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PICList Thread
'Circuit Board Trace thickness'
1997\08\26@125538 by Tim Crist

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    Can anyone tell me what is the minimum thickness for a 1/2 ounce
    copper trace on FR4 would be to carry 1 amp continuous?  FWIW, the
    trace would be about 1/2" long.  I would also be interested in the
    souce of such information.

    TIA,

    Tim

1997\08\26@140031 by David Wong

picon face
According to the IPC-D-275 specs. for a 0.5 oz copper trace to carry an amp
of current you need a thickness of at least 0.030 inches.  The data was
obtained from figure 3-4 from said spec.

David

1997\08\26@141504 by James Musselman

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10C temp rise=  35 mils width
30C temp rise= 18 mils width
source: Bishop Graphics reference book (now out of print, I believe)
James
PS: won't a 1/2"trace have some possible heat sinking to whatever
it is connected to?

----------
{Quote hidden}

1997\08\26@150811 by Site Y

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>On Tue, 26 Aug 1997  Tim Crist <tjcristspamKILLspamCCGATE.HAC.COM> wrote:
>     Can anyone tell me what is the minimum thickness for a 1/2 ounce
>     copper trace on FR4 would be to carry 1 amp continuous?  FWIW,
>     the trace would be about 1/2" long.  I would also be interested in
>     the source of such information.
>

  Try the Printed Circuits Handbook by Coombs, published by McGraw Hill.

  A 100 mills should be adequate.  A more complete answer would depend
on what temperature rise and voltage drop is acceptable in your
application.

Lunchtime,
  Marv

1997\08\26@170531 by Joe Little

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    Can anyone tell me what is the minimum thickness for a 1/2 ounce copper
    trace on FR4 would be to carry 1 amp continuous?  FWIW, the trace would be
    about 1/2" long.  I would also be interested in the source of such
    information.

    Reply--------------------------

    Resistance of the trace can be figured out from the cross sectional area of
    the copper trace , cross sectional area of the plating on the trace,
    resistance of the copper, resistance of the plating, length of the trace.

    Minimum trace width is important for two reasons:

    1) Maximum affordable voltage drop of the trace. The current through the
    trace, its' resistance and ohms law can give you the voltage drop.

    2) How thin can you make it without it burning out.  The current through
    the trace, and its' resistance gives you the power dissipated in the trace,
    and that has an associated temperature rise in the conductor.  The glue
    that holds the copper to the fiberglass can only stand so much heat.
    Pretty soon a hot trace melts the glue, the trace lifts off the board, the
    trace heats even more because the fiberglass was acting like a heat sink,
    and the copper melts and the trace burns out.

    Engineers seem to get picky when it comes to voltage drops and tend to
    widen traces.  PWB designers that are driven to get ten pounds of stuff
    into a 5 pound bag tend to narrow them as much as possible.

    Figure 3-4 in the IPC-D-275, is a set of charts to aid estimating
    temperature rises in traces.  The chart says that for 1 Amp, on a 1/2 ounce
    copper PWB, that a 20 mil wide trace will cause a 20 degree temp rise in
    the trace.  Typical Fiberglass Pwb material is stable up to about 125
    degrees C.  So the pwb can then be used up to 105 degrees ambient.

    You say 20 mil????  Get real.  If the trace is on a connector, then the
    heat from the current through the wire and the gold pin needs to be added.
    Solder is not as good as copper... Add a little heat there.  If its' near a
    hot transistor???? Add some there too.  The Pwb vendor etching traces a
    little thin this week? Add some heat there....

    I typically make traces that carry more than ~100 mA at least as wide as
    pads they run to, and always much wider than the IPC charts allow.  Higher
    currents may require careful planning.  I have run wide traces on all
    available layers, and added copper stubs wherever they fit to make heat
    sinks, and specified extra thick copper plating on the PWB.  You can also
    open up the solder mask along the trace, so that the trace will pick up
    extra solder plating during the wave solder process.

    Sorry about the ranting.... but heat is the enemy and I get a little
    mercenary at times.

    Joe

1997\08\26@172933 by Reginald Neale

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>     Can anyone tell me what is the minimum thickness for a 1/2 ounce
>     copper trace on FR4 would be to carry 1 amp continuous?  FWIW, the
>     trace would be about 1/2" long.  I would also be interested in the
>     souce of such information.
>
>     TIA,
>
>     Tim

You need to specify the width and the max voltage drop and/or temp rise
allowable for your 1/2" trace.

Page 5-35 of the sixth edition of "Reference Data for Radio Engineers" has
a chart. Arguments are oz of Cu, conductor width, current, cross section
and temp rise. If you can't find it, privately email me and I'll look it up
for you.

Reg Neale


'[OT] Thick Film and Dust?'
2000\03\21@200834 by hgraf
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       For one of my 2nd year EE courses I have a report to write dealing with
Thick Film resistors and in a minor way the effect of dust. Does anybody
have any sources (preferably online) dealing with thick film transistor
design and the electrical and thermal effects of dust? Thanks in advance for
any info. TTYL


'[EE]: Troubles with thick solder paste'
2002\03\19@203952 by Djula Djarmati
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Hi,

   A friend of mine is doing SMD assembly and he uses a quite expensive
dispenser - the type with a pneumatic piston in a syringe, timer, different
needles etc.
   He has troubles with the solder paste - it's too thick to dispense
nicely. He tried to dilute the paste with different thinners and it worked
but the flux lost its properties and the solder balls happily oxidized.
  Maybe the solder paste is too old? Can it be rejuvenated? The dispensing
wasn't very smooth even when the paste was new...

Djula

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2002\03\19@205244 by Daniel E. Kleinert Jr.

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If the tube is not being used on a regular basis or was old before you
bought it, the paste will dry out and become hard to use.  You must make
sure you take the tip off after use and cover the tube.

One trick I have had success with is to remove the tip and pump out a good
amount of paste and then put on a new tip.  Hate to be wasteful but it is
better than tossing the entire tube.

Also to possibly save the tube one might try the next size up of tip.  This
is tricky if you are doing a great deal of soldering but is sometimes the
only solution.

Also, I keep the new tubes I buy in the refrigerator until a day or so
before use.  Seems to help keep them fresh.

Dan

At 02:36 AM 3/20/2002 +0100, you wrote:
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'[EE]: What thickness PCB? & cutting?'
2002\11\11@190031 by Tony Harris
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How does one choose what thickness PCB they wish to use?  I have some stuff
that is .064", but I also have some quantity of some REALLY thin copper clad
board.   .032" or maybe less (not sure, my eyes get crosseyed when looking
at it;).  I'd really like to use the .032" stuff I have, but I am not sure
how to determine if a project needs the thicker board.

I have mostly been using .064" (single board purchases and such), but if I
can, I want to use up the other material I have.

Also, on thicker boards, what are you all doing in terms of cutting the
copper clad board?  I still have several 3x5's (or there abouts) but I only
need 3x2's - so far I've been suffering thru hacksawing - anyone have
easier/quicker suggestions?  I have heard of PCB guilliteans (sp?) but I
haven't been able to find small ones in the states (all I seem to find are
"industrial" size units).

Any suggestions would be most appreciated!!

-Tony

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2002\11\11@190846 by Charles Craft

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I've had good luck cutting PCB with a lever blade paper cutter. Not where I
can measure the board material now but it seemed like regular thinkness single
and double-sided PCB material.

chuckc


On Mon, 11 Nov 2002 18:05:29 -0600 Tony Harris <EraseMEtonyspam_OUTspamTakeThisOuTELROYNET.COM> wrote:

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2002\11\11@192545 by Rick C.

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Electrically, no real difference. The .032 will flex a little more but if its in
a box, it shouldn't be a problem. It is easier to cut and drill. You can use a
pair of tin snips or heavy duty shears.

The .0625 (1/16) board is more rigid and will need to be cut with something like
a paper cutter and edges cleaned with a file.
Rick

Tony Harris wrote:

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2002\11\11@232045 by Tony Harris

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> I've had good luck cutting PCB with a lever blade paper cutter. Not where
I
> can measure the board material now but it seemed like regular thinkness
single
> and double-sided PCB material.
>
> chuckc

What kind of paper cutter are you using?  the lever blade I picked up won't
cut thru the thicker boards - feels like I'm going to snap the arm (I think
I may have one that just isn't tough enough for this situation) - the
thinner boards cut easy though.

-Tony

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2002\11\11@232240 by Tony Harris

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> Electrically, no real difference. The .032 will flex a little more but if
its in
> a box, it shouldn't be a problem. It is easier to cut and drill. You can
use a
> pair of tin snips or heavy duty shears.

Well, that is definitly good to know, since I have about 10 12x12 double
sided sheets of the thin stuff.

>
> The .0625 (1/16) board is more rigid and will need to be cut with
something like
> a paper cutter and edges cleaned with a file.

What type do you use more often and how do you cut it?

-Tony

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2002\11\12@014724 by Charles Craft

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www.officedepot.com/shop/catalog/sku.asp?ID=330379&LEVEL=SK

Quartet GT II Series Trimmer, 12"

Stack up 15 sheets of paper and compare to your PCB thickness.

On Mon, 11 Nov 2002 22:25:02 -0600 Tony Harris <RemoveMEtonyspamTakeThisOuTELROYNET.COM> wrote:

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2002\11\12@015824 by Roman Black

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Tony Harris wrote:

> Also, on thicker boards, what are you all doing in terms of cutting the
> copper clad board?   I have heard of PCB guilliteans (sp?) but I
> haven't been able to find small ones in the states (all I seem to find are
> "industrial" size units).


Try any decent office supply shop. They sell
hand-lever guillotines in a few sizes and qualities,
about $40 USD should get you a nice big one. Get one
with metal frame (not plastic) and the strongest
lever blade.
There are good ones and flimsy ones. :o)
-Roman

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2002\11\12@023658 by Jesse Lackey

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I destroyed a good $40 paper cutter after 20 cuts of FR4 board.

I've used a grinding / cutting wheel on a dremel to cut boards, but its
very limited due to wheel / dremel body clearances, creates an enormous
amount of fiberglass dust, and often breaks wheels spectacularly.

I still don't have any sort of good means to cut up PCBs.  Its a
problem.  Hacksaw and nibbler.  Both tedious and make jagged edges.

Anyone?

J

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2002\11\12@025445 by Dominic Stratten

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Fine toothed jigsaw ? Works for me on a high speed. Just take it slowly and
try and support both sides of the board as close to the blade as possible.


{Original Message removed}

2002\11\12@030336 by Robert Rolf

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I've used a cheap paper cutter on .032 board for years. Not too
good for paper now, but I have another 'good' cutter for paper.

Small metal shear. Works great even after hundreds of boards.

Deep scoring both sides with utility knife and metal straight edge,
then breaking the board by pulling up against METAL straight edge while
pinning the board to the table top with great pressure. Make sure
you have at least 0.050 trace clearances to edge to ensure success.

It all depends on what budget you have and how fussy you need to be.

Robert

Jesse Lackey wrote:
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2002\11\12@063346 by Kyrre Aalerud

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If I need to do a board to test on really fast I use 0.8mm board.
Then I can simply cut it with a pair of scissors!

This isn't anything for a production version but is great for a simple
prototype.
They are also thin enough that there may be a printer here somewhere capable
of feeding them...

   Kyrre

{Original Message removed}

2002\11\12@064008 by Philip Pemberton

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Quoting Kyrre Aalerud <EraseMEkreaturespamspamspamBeGoneC2I.NET>:
> If I need to do a board to test on really fast I use 0.8mm board.
> Then I can simply cut it with a pair of scissors!
0.8mm board is also great for DIYing PIC-based smartcards - now most of my
sources have dried up. I used to get them from Crownhill Associates (?), who
could also print a design/photo/whatever onto them. But alas, they have
discontinued the entire range of PIC based smartcards they used to sell...
Perhaps because they found out that people in the satellite TV world were
using them for - shall we say, "illicit" - purposes.

> This isn't anything for a production version but is great for a simple
> prototype.
I just use 1.4mm (standard) SRBP board and dead-bug or copper-island stuff
onto it. I keep the FR4 for high-quality prototypes.

> They are also thin enough that there may be a printer here somewhere
> capable
> of feeding them...
Hmm... Laserprint straight onto a PCB... Is it possible??? Anyone want to
sacrifice a LaserJet II to find out?

Later.
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2002\11\12@081020 by Rick C.

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I've been using my cheap paper cutter for about 25 years and have been cutting
many hundreds of 1/16th boards. It will still cut a single sheet of paper with
precision. I think it is a Premier brand cutter. Any office store like Office
Max or Staples should have something like it. I cut the regular 12X12
sensitized boards purchased from Kepro. Just keep the sheet of thick spacer
paper on the bottom so as not to damage the resist. Use a little pressure to
the inside when pushing the lever down, and walk the 12 inch board into the
cutter (since its only a 8 inch cutting blade). If you search the PIC archives
back about 6 months ago, we went through this discussion in detail.
Rick

Tony Harris wrote:

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2002\11\12@092337 by Dale Botkin

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On Tue, 12 Nov 2002, Jesse Lackey wrote:

> I still don't have any sort of good means to cut up PCBs.  Its a
> problem.  Hacksaw and nibbler.  Both tedious and make jagged edges.

I have to wonder how well a cheap tile saw would work.  They've got
diamond blades that make very thin cuts, and are wet saws to keep the dust
under control.  Nice flat table saw with a guide to keep the piece
straight as it's cut.  And of course water won't bother the fiberglass...
I know you can pick these up at Home Depot or Lowe's pretty cheap.  I used
one to go through porcelain tile like butter.

Dale

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2002\11\12@112304 by Alan B. Pearce

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>And of course water won't bother the fiberglass...

No but ..................

typically for PCB's assembled for use in space, where every solder joint is
getting a visual inspection etc, we specify that the bare PCB be baked for
several hours (typically overnight) at 50C immediately prior to soldering.
This is to free the epoxy of any water content, as moisture will cool the
solder as it flows through a plated through hole, and causes the solder to
go into its pasty, not quite hot enough, won't wet the copper mode. In this
situation you are required to suck the solder out and remake the joint,
which counts as a rework, and with a maximum of 3 reworks to a component
joint, this is highly non-desirable (what were we saying about English as
she is spoke in another thread?).

Yes, water does not bother fibreglass, in that it will not cause
degradation, but it does affect its solderability properties (and I'm sure
someone like RF Jim will tell you that moisture in it will affect its RF
properties).

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2002\11\12@114609 by Dale Botkin

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On Tue, 12 Nov 2002, Alan B. Pearce wrote:

> >And of course water won't bother the fiberglass...
>
> No but ..................

Yeah, but you're in a production environment with stringent controls and
we would assume proper PCB cutting facilities.  I thought this discussion
was about hobbyist and low-volume production.  There is of course nothing
stopping one from baking the PCBs after cutting and before soldering.

As long as some drying technique is used, I'd suspect a minute or so of
exposure to water during cutting would not be a significant (or even a
detectable) detriment to anyone who would be using a tile cutting saw to
cut PCBs instead of whatever a real production facility would use.

Dale

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2002\11\12@121321 by Spehro Pefhany

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At 08:22 AM 11/12/02 -0600, you wrote:
>I have to wonder how well a cheap tile saw would work.  They've got
>diamond blades that make very thin cuts, and are wet saws to keep the dust
>under control.  Nice flat table saw with a guide to keep the piece
>straight as it's cut.  And of course water won't bother the fiberglass...
>I know you can pick these up at Home Depot or Lowe's pretty cheap.  I used
>one to go through porcelain tile like butter.

A shear is the very best way to go, no itchy swarf (very little, anyhow),
and the cuts are always straight. A few hundred bucks to a few thousand
depending on size and brand.

>Best regards

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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'[EE]: What thickness PCB? LJ II'
2002\11\12@131640 by Robert.Rolf

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Philip Pemberton wrote:
> > They are also thin enough that there may be a printer here somewhere
> > capable
> > of feeding them...
> Hmm... Laserprint straight onto a PCB... Is it possible??? Anyone want to
> sacrifice a LaserJet II to find out?

If it were Kapton substrate it might work although the copper would suck
away the fuser heat a bit.
There are minor bends in the path so anything 100% rigid won't work.
You can test it easily by using cereal box cardboard. At worst the rollers
slip.

R

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'[EE]: What thickness PCB? & cutting?'
2002\11\12@180557 by Josh Koffman

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Ironically, I was given a paper cutter today. Big beastie, about 19
inches square. So...does anyone have any tips and techniques they wish
to share about using it to cut PCBs? I'm guessing just holding the board
against the back stop, and cutting it will be best. Will the blade cut
in one motion, or will I need to "hammer" it a bit?

Thanks,

Josh
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fools.
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Charles Craft wrote:
>
> http://www.officedepot.com/shop/catalog/sku.asp?ID=330379&LEVEL=SK
>
> Quartet GT II Series Trimmer, 12"
>
> Stack up 15 sheets of paper and compare to your PCB thickness.

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2002\11\12@182432 by Rick C.

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It's best to use a continuous firm motion, holding the handle with pressure
toward the inside. Sometimes the cut will tend to drift on a curve and the
board will start to twist. Compensate by rotating the board in the opposite
direction of the curve. Hammering the handle with your fist will cause the
cut to drift and possibly get away from you. Watch your fingers too! If you
use factory pre-sensitized bords, leave the spacing paper that comes between
the boards on the bottom to prevent the resist from scratching.
Rick

Josh Koffman wrote:

> Ironically, I was given a paper cutter today. Big beastie, about 19
> inches square. So...does anyone have any tips and techniques they wish
> to share about using it to cut PCBs? I'm guessing just holding the board
> against the back stop, and cutting it will be best. Will the blade cut
> in one motion, or will I need to "hammer" it a bit?
>
>

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2002\11\12@223530 by Josh Koffman

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Do you normally cut with copper up or down? I don't use photosensitive
boards.

Josh
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"Rick C." wrote:
> It's best to use a continuous firm motion, holding the handle with pressure
> toward the inside. Sometimes the cut will tend to drift on a curve and the
> board will start to twist. Compensate by rotating the board in the opposite
> direction of the curve. Hammering the handle with your fist will cause the
> cut to drift and possibly get away from you. Watch your fingers too! If

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2002\11\12@225136 by Rick C.

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Josh Koffman wrote:

> Do you normally cut with copper up or down? I don't use photosensitive
> boards.
>

Never gave it any thought. I guess I always cut with the copper side up. I lay my
negative on the board as a template and cut about a half inch extra all the way
around. This allows for taping the negative, handling of the board and possible
irregularities in the resist near the edges.
Rick

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2002\11\13@005632 by Roman Black

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Dale Botkin wrote:
>
> On Tue, 12 Nov 2002, Alan B. Pearce wrote:
> > >And of course water won't bother the fiberglass...

> Yeah, but you're in a production environment with stringent controls and
> we would assume proper PCB cutting facilities.  I thought this discussion
> was about hobbyist and low-volume production.  There is of course nothing
> stopping one from baking the PCBs after cutting and before soldering.


Which is not hard, we have a wooden box with a
100W light globe and a couple of wire "kitchen"
racks and temp control which is 3 transistors
a pot and a 240v relay. It regulates temperature
very well and cost almost nothing to build. I
think the dearest part was a $7 digital thermometer.

Being able to dry boards and cure glues and inks
at 40'C or 50'C is very handy, it is one of our
most used pieces of equipment.

Another handy technique is to put the board on
the table and a 60W "arm type" desk lamp 3"
above it, this gives a fairly constant 50'C.
-Roman

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2002\11\13@032447 by Ashley Roll

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Hi Everyone,

Tile Saws work Great!

I bought one about a year ago and use it for PCBs..

They have a diamond blade which eats fibreglass like butter :) The edges are
ground smooth (assuming that you can move the PCB without going all over the
place - I use the guide and run the board edge along it. Just like a table
top saw for wood.

The blade that came with mine is about 3mm wide, but you can purchase
replacements that are much thinner.

The only problem is that you do need the water to keep the blade cool and to
stop the dust, but it gets EVERYWHERE! (you'll get damp if not wet when
using it) and when it dries out there is fibreglass powder where the water
was, but a little care and this is not too much of a problem.

Cheers,
Ash.

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> {Original Message removed}

2002\11\13@043012 by Alan B. Pearce

face picon face
Dale Botkin wrote:
>
> On Tue, 12 Nov 2002, Alan B. Pearce wrote:
> > >And of course water won't bother the fiberglass...

> Yeah, but you're in a production environment with stringent controls and
> we would assume proper PCB cutting facilities.  I thought this discussion
> was about hobbyist and low-volume production.  There is of course nothing
> stopping one from baking the PCBs after cutting and before soldering.

Hmm, for some reason Dale's reply didn't make it to me, so I'll use Roman's
quote

Yeah, sure we are doing it in a production environment, but I was more
thinking of the warning about having moisture impregnated fibreglass, and
wondering why your solder joints keep turning up as dry joints right at the
critical time in testing immediately before delivery :))) Certainly baking
the PCB's (well just put it in the oven after Mum has finished cooking
dinner, while the oven cools down) is worth doing to get around this
problem.

--
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'calculator for PCB route thickness'
2006\01\20@033340 by Vasile Surducan
face picon face
Hi all,

A few time ago there was a discussion about computing PCB routes thick
and a link for an online calculator.
Do you know the link address ?

thx,
Vasile

2006\01\20@204657 by Alex Parkinson

flavicon
face
Is this what you're looking for?

http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm

Alex

Vasile Surducan wrote:
> Hi all,
>
> A few time ago there was a discussion about computing PCB routes thick
> and a link for an online calculator.
> Do you know the link address ?
>
> thx,
> Vasile
>
>  

2006\01\21@144205 by Vitaliy

flavicon
face
Vasile wrote:
> A few time ago there was a discussion about computing PCB routes thick
> and a link for an online calculator.
> Do you know the link address ?

http://www.circuitcalculator.com/4pcb/trace_width_calculator.php

Best regards,

Vitaliy

2006\01\21@163402 by Shawn Wilton

picon face
An even more robust link:  <
http://www.google.com/search?hl=en&q=pcb+trace+width+calculator&btnG=Google+Search
>

More copies of that script than you can shake a stick at.

On 1/21/06, Vitaliy <spamEraseMEspammaksimov.org> wrote:
{Quote hidden}

> -

2006\01\22@012458 by Vasile Surducan

face picon face
Thanks all,
I've seen that all people here are doing pcb computation almost the same.
More, some sites are just copies of other sites.

greetings,
Vasile

On 1/21/06, Shawn Wilton <RemoveMEblack9EraseMEspamspam_OUTgmail.com> wrote:
{Quote hidden}

2006\01\22@043402 by Shawn Wilton

picon face
Yeah, as far as I could tell they were all based on calculations from the
same paper.  Pick your favorite and bookmark it.

On 1/21/06, Vasile Surducan <EraseMEpiclist9spam@spam@gmail.com> wrote:
{Quote hidden}

>


'[EE] "Shear thickening fluid" provides flexible ar'
2006\09\06@080040 by Russell McMahon
face
flavicon
face
For a graphic demonstration of this sort of effect add water to a few
tablespoons of cornflour until you have a paste on the wet side of
stiff and then try stirring it with a spoon at various speeds. The
properties are quite mind boggling.

       http://www.timesonline.co.uk/article/0,,2087-2340507,00.html

"
SOLDIERS are to begin trialling a futuristic “liquid armour” that is
worn like ordinary clothing but turns into a rigid shield as soon as
it is hit by bullets or shrapnel.
The armour consists of material impregnated with liquid silica that
has been modified using nanotechnology. It is designed as a flexible
alternative to the current military armour, which consists of Kevlar
material reinforced by heavyweight ceramic plates.


The American army hopes to use the liquid armour — which has been
likened to the skin of cyborgs in films such as Terminator and
RoboCop — in a new combat outfit that will enter service in 2010.
British troops are also examining the concepts behind the armour, the
technical name of which is shear thickening fluid (STF), for the
Ministry of Defence’s Future Infantry Soldier Technology project.
“We can’t yet say STF will stop every bullet, but we are already
seeing how it provides enhanced protection for less weight,” said Eric
Wetzel, the co-inventor of the substance at the US Army Research
Laboratory’s materials centre in Natick, Massachusetts.
A small British company, d3o Lab based in Hove, East Sussex, has
already developed an STF-based foam that provides extra stiffening
against impact in commercial products such as goalkeeper gloves,
snowboarding shoes and ski suits. But the American armour, developed
in conjunction with the University of Delaware, goes much further.
The silica nanoparticles in STF move around like a liquid under normal
conditions, but when struck lock together in a solid lattice-like
structure that lasts only as long as the impact.
A lightweight vest impregnated with STF has already been tested and
has proved able to stop knife-stabs, fragmentation blasts, lower-power
bullets and even hypodermic needles. At this level of development, it
is suitable for staff such as police and prison officers.
The next stage is to strengthen the armour sufficiently to withstand
high-velocity bullets and shrapnel from roadside bombs.
American and British officials are anxious to improve the
effectiveness of body armour because of the constant stream of deaths
and injuries in Iraq and Afghanistan.
Conventional Kevlar body armour with ceramic plate inserts has cut the
death rate, but is heavy and unwieldy and leaves legs and arms
vulnerable to severe wounds."

2006\09\06@230359 by Gus S Calabrese

face picon face
^I want this for motorcycle helmets and other civilian-type armour.
AGSC^


On 2006-Sep 06, at 05:57hrs AM, Russell McMahon wrote:

For a graphic demonstration of this sort of effect add water to a few
tablespoons of cornflour until you have a paste on the wet side of
stiff and then try stirring it with a spoon at various speeds. The
properties are quite mind boggling.

        http://www.timesonline.co.uk/article/0,,2087-2340507,00.html

"
SOLDIERS are to begin trialling a futuristic “liquid armour” that is
worn like ordinary clothing but turns into a rigid shield as soon as
it is hit by bullets or shrapnel.
The armour consists of material impregnated with liquid silica that
has been modified using nanotechnology. It is designed as a flexible
alternative to the current military armour, which consists of Kevlar
material reinforced by heavyweight ceramic plates.


The American army hopes to use the liquid armour — which has been
likened to the skin of cyborgs in films such as Terminator and
RoboCop — in a new combat outfit that will enter service in 2010.
British troops are also examining the concepts behind the armour, the
technical name of which is shear thickening fluid (STF), for the
Ministry of Defence’s Future Infantry Soldier Technology project.
“We can’t yet say STF will stop every bullet, but we are already
seeing how it provides enhanced protection for less weight,” said Eric
Wetzel, the co-inventor of the substance at the US Army Research
Laboratory’s materials centre in Natick, Massachusetts.
A small British company, d3o Lab based in Hove, East Sussex, has
already developed an STF-based foam that provides extra stiffening
against impact in commercial products such as goalkeeper gloves,
snowboarding shoes and ski suits. But the American armour, developed
in conjunction with the University of Delaware, goes much further.
The silica nanoparticles in STF move around like a liquid under normal
conditions, but when struck lock together in a solid lattice-like
structure that lasts only as long as the impact.
A lightweight vest impregnated with STF has already been tested and
has proved able to stop knife-stabs, fragmentation blasts, lower-power
bullets and even hypodermic needles. At this level of development, it
is suitable for staff such as police and prison officers.
The next stage is to strengthen the armour sufficiently to withstand
high-velocity bullets and shrapnel from roadside bombs.
American and British officials are anxious to improve the
effectiveness of body armour because of the constant stream of deaths
and injuries in Iraq and Afghanistan.
Conventional Kevlar body armour with ceramic plate inserts has cut the
death rate, but is heavy and unwieldy and leaves legs and arms
vulnerable to severe wounds."

2006\09\07@035713 by Russell McMahon

face
flavicon
face
^I want this for motorcycle helmets and other civilian-type armour.
AGSC^

You want a cornflour motorcycle helmet ? :-)

       R


On 2006-Sep 06, at 05:57hrs AM, Russell McMahon wrote:

For a graphic demonstration of this sort of effect add water to a few
tablespoons of cornflour until you have a paste on the wet side of
stiff and then try stirring it with a spoon at various speeds. The
properties are quite mind boggling.

        http://www.timesonline.co.uk/article/0,,2087-2340507,00.html

'[EE]: High Speed Thickness Measurement'
2006\09\25@134222 by John

flavicon
face
Hi Guys

I would like some suggestions for a thickness measurement project that I
have in mind. Its purpose when built will be to measure the thickness of
tissue coming out of a paper machine - ave speed 1500m/min

The standard means involve radioactive sensors or laser. Does anyone have
any suggestions for alternatives?

I am planning to base the design around an ARM processor. It needs to
provide a data stream, a digital output to show a warning alarm, a digital
output for paper break, aswell as a configurable 4-20mA output. The data
stream will be fed into a Honeywell DCS.

My main concern at this stage is choosing the measurement head - maybe even
designing one. I feel that it may need an array of sensors spread across the
sheet so that the even-ness of the sheet can be measured too. The
measurement heads could be mounted on an oscillating arm if need be.

Regards

John

2006\09\25@143950 by Steve Smith

flavicon
face
This a stupid (maybe) idea (long way out of my field)

Light permeability
For a lamp of given intensity the translucence of the sheet could be used as
a thickness measurement

Regards Steve

{Original Message removed}

2006\09\25@145945 by Vasile Surducan

face picon face
On 9/25/06, John <johnspamBeGonespamraystorm.co.uk> wrote:
> Hi Guys
>
> I would like some suggestions for a thickness measurement project that I
> have in mind. Its purpose when built will be to measure the thickness of
> tissue coming out of a paper machine - ave speed 1500m/min

Microwave around 10Ghz, if the paper's temperature and moisture are constant.

Vasile

2006\09\25@150324 by John

flavicon
face




> This a stupid (maybe) idea (long way out of my field)
>
No Idea is stupid Steve, thanks for the suggestion

> Light permeability
> For a lamp of given intensity the translucence of the sheet could be used
as
> a thickness measurement
This could work if the light source is self calibrating, allowing for the
gradual degradation of the lamp.

Anyone know how well this could be used to measure a change of fractions of
a micron?

Regards

John

>
> Regards Steve
>
> {Original Message removed}

2006\09\25@151833 by John

flavicon
face
Something just occured to me -

Light is probably not the best because tissue production is very dusty, so
the light sensors will end up covered in dust, unless theyre continually
washed off.

Regards

John
----- Original Message -----
From: "Steve Smith" <RemoveMExygax@spam@spamspamBeGoneblueyonder.co.uk>
To: "'Microcontroller discussion list - Public.'" <.....piclist@spam@spamEraseMEmit.edu>
Sent: Monday, September 25, 2006 6:38 PM
Subject: RE: [EE]: High Speed Thickness Measurement


> This a stupid (maybe) idea (long way out of my field)
>
> Light permeability
> For a lamp of given intensity the translucence of the sheet could be used
as
> a thickness measurement
>
> Regards Steve
>
> {Original Message removed}

2006\09\25@152220 by John

flavicon
face
Hi Vasile

The temp and moisure content vary.

Temp is dependant on the amount of steam being fed into the dryer drum, and
the speed of the machine - both operator set. The moisture content varies
depending on what the product requirement is - budget to luxuary and many
stages inbetween.

This doesnt mean that it cant be calibrated according to the conditions - it
will just make it a very complex measurement.

Regards

John
{Original Message removed}

2006\09\25@162303 by Bob Axtell

face picon face
I believe that thickness measurement is done with a radioactive source
and a "geiger" counter. The
thicker the material, the more attenuation. Easily calibrated.

--Bob

John wrote:
{Quote hidden}

> {Original Message removed}

2006\09\25@231209 by Vasile Surducan

face picon face
On 9/25/06, John <.....johnRemoveMEspamraystorm.co.uk> wrote:
> Hi Vasile
>
> The temp and moisure content vary.
>
> Temp is dependant on the amount of steam being fed into the dryer drum, and
> the speed of the machine - both operator set. The moisture content varies
> depending on what the product requirement is - budget to luxuary and many
> stages inbetween.
>
> This doesnt mean that it cant be calibrated according to the conditions - it
> will just make it a very complex measurement.

20 years ago we've designed 10GHz moisture meters for some similar
"sheet" type DUT.
There are now on the market complex moisture meters in microwave range
measuring three parameters: moisture, temperature and thickness of the
material. Thickness is a constant inside the algorithm but could be
easily recalibrated for becoming the measuring parameters. I had an
advertising issue printed somewhere but probably will be hard to found
it now.

Vasile

2006\09\26@040142 by Alan B. Pearce

face picon face
>> This a stupid (maybe) idea (long way out of my field)
>>
>No Idea is stupid Steve, thanks for the suggestion

So here is my suggestion. Assuming the paper can be run over a rounded
surface (it could be an existing guide roller) so that you know it is flat
against the surface (i.e. under some tension), then my thought was to use
ultrasonic sensors to measure the thickness difference between the paper
height and the roller. You could have a number of sensors across the width
of the paper if necessary.

>> Light permeability
>> For a lamp of given intensity the translucence of the sheet
>> could be used as a thickness measurement
>> This could work if the light source is self calibrating,
>> allowing for the gradual degradation of the lamp.
>
>Anyone know how well this could be used to measure a change
>of fractions of a micron?

Yes. The way I would do it, taking the roller arrangement I suggested above,
is to shine the light so it is shining along the tangent of roller onto a
linear CCD. The roller will cause a shadow, which you use as reference, and
the paper will increase the shadow height. Readout speed will probably be
limited to the clockout rate of the CCD.

2006\09\26@044324 by Russell McMahon

face
flavicon
face
Id have thought that capacitive measurement could be quite accurate
for this.


       Russell


2006\09\26@045251 by John

flavicon
face
Thanks for the ideas guys.

I will investigate the use of ultrasonic, because the final stage had a
number of rollers on which this could work.

I am also interested in the 10GHz meter because it provides other
interesting measurements.

Will keep you all posted on progress as it forges on.

Regards

John
{Original Message removed}

2006\09\26@050429 by John

flavicon
face
Hi Russell

How would you do this? I can imagine using the sheet as the dielectric
between 2 plates. Would a tiny change in thickness create enough variance of
capacitance to measure accurately?

Regards

John
----- Original Message -----
From: "Russell McMahon" <.....apptechSTOPspamspam@spam@paradise.net.nz>
To: "Microcontroller discussion list - Public." <piclistEraseMEspam@spam@mit.edu>
Sent: Tuesday, September 26, 2006 8:38 AM
Subject: Re: [EE]: High Speed Thickness Measurement


> Id have thought that capacitive measurement could be quite accurate
> for this.
>
>
>         Russell
>
>
> --

2006\09\26@084558 by Rolf

face picon face
part 0 44 bytes
his is a multi-part message in MIME format.
part 1 3253 bytes content-type:text/plain; charset=ISO-8859-1; format=flowed (decoded 7bit)

Since I have absolutely no idea about this sort of industrial control,
let me throw in my one idea...

... how about oblique laser light, and measuring the change in reflected
distance... let me explain...

Run the tissue over a a roller which is measured precisely. Put a sensor
which can detect the wavelength of the laser light immediately above the
paper with perhaps a light tube.

Shine the laser at a very oblique angle on to the tissue, and measure
the angle you need to shine the laser on in order to get the beam under
the light tube... like this... actually, perhaps a better method will be
to shine the laser at a known but very oblique angle, and to then use a
"heliostat" mechanism to track where the dot is reflected... like the
attached image. The thickness of the tissue will be proportional to the
angle you have to adjust the sensor to to get the sensor pointed at the
laser dot.

Rolf

John wrote:
{Quote hidden}

> {Original Message removed}

2006\09\26@093645 by John

flavicon
face
Hi Rolf

I kinda like this one. It allows the light source and sensor to be located
away from the machine workings. It also makes for easy experimentation on a
live systemwithout affecting production. Thanks

Regards

John
{Original Message removed}

2006\09\26@120338 by Russell McMahon

face
flavicon
face
> How would you do this? I can imagine using the sheet as the
> dielectric
> between 2 plates. Would a tiny change in thickness create enough
> variance of
> capacitance to measure accurately?

If you can maintain a sensor at a small distance above the paper as it
eg travels over a roller then the change in capacitance should be
highly proportional to paper thickness. Dielectric constant of paper
relative to air (1) governs how large a swing you'll get.



       Russell


2006\09\26@124033 by Dominic Stratten

picon face
Dont forget the vast amounts of static these machines generate.

I used to run a paper converting machine many many years ago and the sparks
from the static generated by the paper unrolling, cutting and re-rolling was
enough to jump 3 or 4 inches.

I still have nightmares to this day about walking up to the machine and
getting zapped by a couple of hundred thousand volts lol.

Dom
{Original Message removed}

2006\09\26@125643 by John

flavicon
face
Hi Dom

I am not sure how they combat static on our machine, all I know is that I
havent been shocked yet. It may be because most of the process is wet, with
only the very last stage being drying, creping and rolling onto the reel.

Cheers

John.
{Original Message removed}


'[EE] "Shear thickening fluid" provides flexible ar'
2006\10\15@223746 by Sean Schouten
face picon face
On 9/7/06, Russell McMahon <RemoveMEapptechspamspamBeGoneparadise.net.nz> wrote:
>
> ^I want this for motorcycle helmets and other civilian-type armour.
> AGSC^
>
> You want a cornflour motorcycle helmet ? :-)
>
>         R
>


I just fell off of my chair after reading that! lol.

2006\10\15@233853 by Jinx

face picon face

> > You want a cornflour motorcycle helmet ? :-)
>
> I just fell off of my chair after reading that! lol.

So we need them for reading too now ? Jeepers, not
safe anywhere are we.....


'[EE] minimum multilayer PCB thickness&prepreg'
2006\11\08@015024 by Vasile Surducan
face picon face
Hi,

Which is the minimum PCB thickness per layer pairs you have ever used
for a multilayer (10 or more layer) board ?
3 mil for prepreg and 3 mil for PCB thickness could be a feasable
dimension for a hitech PCB manufacturing house ?
If yes, who is the manufacturer ?
Have you ever measured the epsilon of the prepreg ?
thx,
Vasile

2006\11\08@022611 by Tamas Rudnai

face picon face
10 layers? Where do you need that many?

Tamas


On 08/11/06, Vasile Surducan <spamBeGonepiclist9KILLspamspam@spam@gmail.com> wrote:
{Quote hidden}

> -

2006\11\08@025333 by Xiaofan Chen

face picon face
On 11/8/06, Tamas Rudnai <tamas.rudnaispam_OUTspam@spam@gmail.com> wrote:
> 10 layers? Where do you need that many?
>
> Tamas
>

For example, a planar transformer (2 isolated primary windings + 6
isolated secondary windings).

2006\11\08@054900 by Alan B. Pearce

face picon face
> 10 layers? Where do you need that many?

Would be quite easy with high density of BGA chips on a PCB.


'[EE] converting PCB copper thickness specs'
2007\06\22@155740 by James Newton, Host
face picon face
How does one convert oz/ft2 into mils as it relates to the thickness of
copper on a PCB?

The other day, a question was asked about calculating trace width for a
given current, etc... And one of the sites that came up as an answer belongs
to an ex-piclister who gave me permission to copy his trace with calculation
javascript. I wanted to make some minor changes to it (temperatures in F as
well as C) and feature creep led me to want to automatically convert the C
value to F and back as the units were changed which then led to me wanting
to add that feature for the other unit selectable fields, one of which is
oz/ft2 or mils for copper thickness.

But Google doesn't seem to know how to do that conversion. Any ideas? I seem
to be too stupid to figure it out today.

BTW the new page is at
http://www.piclist.com/techref/pcb_traces.htm

---
James Newton: PICList webmaster/Admin
spamBeGonejamesnewton@spam@spampiclist.com  1-619-652-0593 phone
http://www.piclist.com/member/JMN-EFP-786
PIC/PICList FAQ: http://www.piclist.com


2007\06\22@163233 by Snail Instruments

flavicon
face

>How does one convert oz/ft2 into mils as it relates to the thickness of
>copper on a PCB?

It should be converted thru copper density, which is 8 920
kilogram/cubic meter = 8 910 oz/ft3.

>to add that feature for the other unit selectable fields, one of which is
>oz/ft2 or mils for copper thickness.

Yet another way is thickness in micrometers.

Josef


2007\06\22@164325 by Sean Breheny

face picon face
Hi James and Josef,

My notes show 1.4 mils (thousandths of an inch) per oz/ft2. I think I
got that from one of the online PCB calculator sites.

Sean


On 6/22/07, Snail Instruments <RemoveMEsnailEraseMEspamKILLspamsnailinstruments.com> wrote:
{Quote hidden}

> -

2007\06\22@171923 by James Newton, Host

face picon face
> >How does one convert oz/ft2 into mils as it relates to the
> thickness of
> >copper on a PCB?
>
> It should be converted thru copper density, which is 8 920
> kilogram/cubic meter = 8 910 oz/ft3.

Errr.. Huh? Yes I really am that dumb when it comes to this sort of thing.

Let me try again:

If I have copper thickness in mills, what mathematical formula yields
oz/ft2?

If I have copper thickness in oz/ft2, what mathematical formula yields
mills?

> >to add that feature for the other unit selectable fields,
> one of which
> >is
> >oz/ft2 or mils for copper thickness.
>
> Yet another way is thickness in micrometers.

K. Give me a set of formula and I'll add another option.


Thanks for trying to help.

---
James.


2007\06\22@174544 by Peter P.

picon face
James Newton, Host <jamesnewton <at> piclist.com> writes:

> How does one convert oz/ft2 into mils as it relates to the thickness of
> copper on a PCB?

convert oz/ft^2 -> grams/cm^2

then insert copper density (from Wikipedia:copper): rho = 8.96 g/cm^3 @ 20C

so the thickness is: h [cm] = grams / ( rho * 1 cm^2 )

convert to mils or pounds or carats or whatever.

Peter P.


2007\06\22@174955 by Sean Breheny

face picon face
Hi James,

volume density=area density/thickness

therefore:

thickness=area density/volume density
area density=volume density*thickness

Using Josef's numbers, we have:

thickness (in feet)=area density (oz/ft2)/8910 (oz/ft3)

For 1 oz/ft2, this gives 1.12e-4 feet or 1.34 thousandths of an inch
(just about what I had).

To put the formula itself into thousandths, multiply by 12000:

thickness (mils)=1.35*area density (oz/ft2)

The reverse formula would then be:

area density (oz/ft2)=thickness(mils)/1.35

Sean


On 6/22/07, James Newton, Host <spamBeGonejamesnewtonspam_OUTspamRemoveMEpiclist.com> wrote:
{Quote hidden}

> -

2007\06\22@175928 by Kevin Timmerman

flavicon
face

>If I have copper thickness in mills, what mathematical formula yields
>oz/ft2?
>
>If I have copper thickness in oz/ft2, what mathematical formula yields
>mills?

oz * 1.4 = mils

mils / 1.4 = oz

2007\06\22@181729 by Hector Martin

flavicon
face
James Newton, Host wrote:
> But Google doesn't seem to know how to do that conversion. Any ideas? I seem
> to be too stupid to figure it out today.

Sure it does. Here's the link to get the conversion constant - note the
lack of any explicit calculations (save for the inverse - take it out
and reverse the output units for the inverse conversion constant);
Google figured the units out itself.
http://tinyurl.com/2rklt7
(where 8.96g/cm^3 is the density of copper)

Here's how you go one way:
http://tinyurl.com/2ubxn8
And here's the other:
http://tinyurl.com/2udow5

Of course, you have to input the density of copper with proper units,
but you can't expect Google to assume you're dealing with copper!

As an aside, I've found Google to be a very good aid when doing
technical calculations like these, not only because it auto-handles
units (which is useful but can get strange sometimes), but because if
you mess up the units anywhere it will either not return an answer or
give out the wrong units.

--
Hector Martin (.....hectorspamRemoveMEmarcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

2007\06\22@181948 by James Newtons Massmind

face picon face
Thanks very much Sean, I've updated the program.

---
James.



{Quote hidden}

2007\06\23@025553 by Vasile Surducan

face picon face
On 6/22/07, Snail Instruments <spamBeGonesnailspam@spam@snailinstruments.com> wrote:
>
> >How does one convert oz/ft2 into mils as it relates to the thickness of
> >copper on a PCB?
>
> It should be converted thru copper density, which is 8 920
> kilogram/cubic meter = 8 910 oz/ft3.
>
> >to add that feature for the other unit selectable fields, one of which is
> >oz/ft2 or mils for copper thickness.
>
> Yet another way is thickness in micrometers.

Which is the correct way used even on clever american PCB houses
(which are trying with efforts to change everything on metric system).
see:
http://www.pcblibraries.com/forum/
or
http://www.pcblibraries.com/resources/GEN-docs.asp

0.5 oz = 17.5 um = 0.7mil (rounded value)
1 oz = 35 um = 1.4mil (rounded value)

Vasile

2007\06\23@084325 by Gerhard Fiedler

picon face
Hector Martin wrote:

> As an aside, I've found Google to be a very good aid when doing
> technical calculations like these, not only because it auto-handles
> units (which is useful but can get strange sometimes), but because if
> you mess up the units anywhere it will either not return an answer or
> give out the wrong units.

Which is of course a general advantage of doing calculations with the
proper units throughout (including conversion factors). In many cases,
you'll see immediately when something is wrong. I'm glad that I was
introduced to physics in high school this way and have it done like this
ever since.

Gerhard

2007\06\23@091255 by Carl Denk

flavicon
face
The units (grams, ounces, feet, meters, or whatever) should be carried
along with the numbers, and then crossed out when able to cancel. Then
remaining will be ONLY  the final units, which must be what you are
looking for. :)

Gerhard Fiedler wrote:
{Quote hidden}

2007\06\23@151141 by Hector Martin

flavicon
face
Gerhard Fiedler wrote:
> Which is of course a general advantage of doing calculations with the
> proper units throughout (including conversion factors). In many cases,
> you'll see immediately when something is wrong. I'm glad that I was
> introduced to physics in high school this way and have it done like this
> ever since.

Of course - this is the way I do it. However, you can make mistakes with
units in much the same way you can mess up numbers when doing things on
paper. For example, you could inadvertently flip a unit around when
cancelling things out (essentially taking the reciprocal). Google is to
calculations with units as a calculator is to calculations without
units. Sometimes there just isn't enough time to do it carefully, too -
with today's education, sometimes there is way too much
formula-crunching. Google serves as a nice doublecheck on your formula
units vs. operations, as well as calculating the answer at the same time.

As for conversion factors, I try to use SI throughout most things to
avoid them - if you do the full copper thickness calculation by hand,
you'll see most of the work is due to the use of funky imperial units.


--
Hector Martin (RemoveMEhectorspam_OUTspammarcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

2007\06\23@204722 by Gerhard Fiedler

picon face
Hector Martin wrote:

> As for conversion factors, I try to use SI throughout most things to
> avoid them

Unluckily it seems that Google Calculator doesn't understand a number of
proper SI units, at least not the standard abbreviation.

> if you do the full copper thickness calculation by hand, you'll see most
> of the work is due to the use of funky imperial units.

Yes, that's why I have somewhere stored in non-volatile memory that 1 oz of
copper is roughly equivalent to 35 um thickness :)

Gerhard

2007\06\25@211817 by peter green

flavicon
face
Carl Denk wrote:
> The units (grams, ounces, feet, meters, or whatever) should be carried
> along with the numbers, and then crossed out when able to cancel. Then
> remaining will be ONLY  the final units, which must be what you are
> looking for. :)
>
>  
The problem I find with trying to do this is that in many cases the unit
symbols are the same bloody letters as the variable names. Maybe some
people have handwriting where upright and italic can be distinguished
but I sure as hell don't.


2007\06\25@212633 by Carl Denk

flavicon
face
If need be just spell out long  hand, but the method was one of the
first things I learned as a freshman at Univ. of Mich. in 1960, and I
still do it. :)

peter green wrote:
{Quote hidden}

2007\06\26@163018 by Gerhard Fiedler

picon face
peter green wrote:

>> The units (grams, ounces, feet, meters, or whatever) should be carried
>> along with the numbers, and then crossed out when able to cancel. Then
>> remaining will be ONLY  the final units, which must be what you are
>> looking for. :)
>
> The problem I find with trying to do this is that in many cases the unit
> symbols are the same bloody letters as the variable names. Maybe some
> people have handwriting where upright and italic can be distinguished
> but I sure as hell don't.

I've never found this to be a problem. A unit never comes alone; it always
follows a number. A variable never follows a number without an operator in
between. (Ok, there's the math shortcut of "6 A" that could mean "six times
the variable A", but usually the context makes clear what is meant, and if
not, you can make the implied multiplication operator explicit.) Also
normally I either work in variables (on the right side) or in numbers;
rarely mixed.

Gerhard


'[EE] 2D graphics: Drawing thick lines?'
2007\10\16@222145 by M. Adam Davis
face picon face
So I've implemented a line drawing algorithm, and even understand how
to draw anti-aliased lines

But I haven't seen anything about drawing lines of varying width.

I suspect that simply drawing several single pixel wide lines adjacent
to each other will leave unmarked pixels interior to the overall line
in many cases with the default bresenham line algorithm.

I suspect that the "correct" method is to draw a filled polygon (or
filled rectangle).

But I'm hoping there's an easier answer.

Any pointers or clues?

This is going on an ARM processor with an LCD controller, but no
graphics accelerator.  It is running Linux, and I've looked at a
variety of graphics libraries, but the majority appear to target X
(which I'm not running), and the others don't appear to do what I need
or are poorly supported to the point where implementing my own
primitives appears to be speedier than trying to get their code
working on this embedded platform.  This is going straight to a frame
buffer, but I've already got the pixel routines (including alpha
blending).

Ultimately I want to be able to draw semi-transparent open polygons
(non filled) with borders that are more than one pixel wide.

Any ideas or suggested appreciated.  I'll probably have to implement
this next week (hey, I'm planning ahead - who'd'a thunk it?)

Of course, as usual the project is growing in complexity the further I
pursue it, so any suggestions on simple windowing libraries with
framebuffer/alpha/PNG/font support would be appreciated as well.  As
would suggestions for mailing lists and forums where such information
can more eaily be found.

-Adam

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2007\10\17@000157 by Marcel Birthelmer

picon face
Adam,
you could try going through the math for your line-drawing algorithm,
but using a virtual grid where each virtual pixel is NxN pixels of
your actual buffer. That way, the line would end up appropriately
fatter.
- Marcel

On 10/16/07, M. Adam Davis <stienmanspamspamgmail.com> wrote:
{Quote hidden}

> -

2007\10\17@041042 by Peter P.

picon face
M. Adam Davis <stienman <at> gmail.com> writes:
> So I've implemented a line drawing algorithm, and even understand how
> to draw anti-aliased lines
>
> But I haven't seen anything about drawing lines of varying width.

Almost all raster renderers use byte or word wide storage in the display section
(not last for speed reasons). So optimizing for pixel drawing will not help so
much. In most raster rendering systems the general case can be studied using a
'mini-screen' made up of 2 x 2N words of storage, where N is the number of
pixels in a word. This assumes that most lines drawn are less than sqrt(N)
pixels wide. This results in 4 cases of this 2x2N matrix for any line to be
drawn, of any length and of any thickness between 1 and sqrt(N):

1. the matrix holding the start of the line
2. the matrix holding the end of the line
3. the matrix holding any middle section(s) of the line (this one repeats)
4. in the special case where the line is short, and both start and end fir in 1
matrix.

This makes the drawing a tiling operation. Also inside the tiles drawing is done
bit-range by bit-range not bit by bit. So there are algorythms but there is no
general easy way to fit them to any word width (and bit plane depth). The matrix
looks like so:

AAAA BBBB
CCCC DDDD
EEEE FFFF
GGGG HHHH

IIII JJJJ
KKKK LLLL
MMMM NNNN
OOOO PPPP

for N=4 and scan from left to right and top to bottom. There are other possible
arrangements for other scan schemes.

Peter P.


2007\10\17@052337 by peter green

flavicon
face

>> But I'm hoping there's an easier answer.
>>    
Use bresenhams or similar but rather than plotting a single pixel at
each location plot a  cluster of pixels.

Using a larger grid is a bad idea because it will make the line far
rougher than it needs to be, you should still plot at every location you
normally would.



2007\10\17@083245 by M. Adam Davis

face picon face
On 10/17/07, Peter P. <spam_OUTplpeter2006spam_OUTspamspam_OUTyahoo.com> wrote:
> M. Adam Davis <stienman <at> gmail.com> writes:
> > So I've implemented a line drawing algorithm, and even understand how
> > to draw anti-aliased lines
> >
> > But I haven't seen anything about drawing lines of varying width.
>
> Almost all raster renderers use byte or word wide storage in the display section
> (not last for speed reasons). So optimizing for pixel drawing will not help so
> much. In most raster rendering systems the general case can be studied using a
> 'mini-screen' made up of 2 x 2N words of storage, where N is the number of
> pixels in a word. This assumes that most lines drawn are less than sqrt(N)
> pixels wide. This results in 4 cases of this 2x2N matrix for any line to be
> drawn, of any length and of any thickness between 1 and sqrt(N):

So, my display is 15 bit (16 bit ignored), and a 32 bit processor.
Therefore N = 2 (two pixels per word).

The mini screen you mention would therefore require 8 words (32 bytes,
256 bits) of storage, and in this mini screen I could not have lines
wider that 1.414 pixels.

> 1. the matrix holding the start of the line
> 2. the matrix holding the end of the line
> 3. the matrix holding any middle section(s) of the line (this one repeats)
> 4. in the special case where the line is short, and both start and end fir in 1
> matrix.

I assume you're talking about vectors here.  I hadn't thought about
that - time to pull out my linear algebra book and see what it has.

{Quote hidden}

Is there a name or set of terms that characterize this method so I
could do more research?  I admit to being lost here...

Thanks for your time!

-Adam

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2007\10\17@083621 by M. Adam Davis

face picon face
Peter,

Thanks.  If I did this (and I'm considering it) I'd have to make
another buffer to hold the result, then overly it on top of the screen
as it needs to be alpha transparent.  If I wrote it directly to the
screen some pixels would be written more than once, falsely
multiplying the alpha effect.  Before I did this I'd probably
implement polygons and do it that way.

Unless there's some secret cluster that guarantees each pixel gets
written exactly once...

-Adam

On 10/17/07, peter green <plugwashspam_OUTspamp10link.net> wrote:
{Quote hidden}

> -

2007\10\17@092351 by Peter P.

picon face
M. Adam Davis <stienman <at> gmail.com> writes:
> So, my display is 15 bit (16 bit ignored), and a 32 bit processor.
> Therefore N = 2 (two pixels per word).
>
> The mini screen you mention would therefore require 8 words (32 bytes,
> 256 bits) of storage, and in this mini screen I could not have lines
> wider that 1.414 pixels.

More like sqrt(2)*N . My mistake.

Anyway the mini matrix makes it easy to deal with chamfer and line ending
stuff that is otherwise horrible to deal with in a 'pure' math solution.

> > 1. the matrix holding the start of the line
> > 2. the matrix holding the end of the line
> > 3. the matrix holding any middle section(s) of the line (this one repeats)
> > 4. in the special case where the line is short, and both start and end
> > fit in 1
> > matrix.
>
> I assume you're talking about vectors here.  I hadn't thought about
> that - time to pull out my linear algebra book and see what it has.

Not vectors but sprites ... the mini-matrix is used to tile the scan storage
thus drawing the line. The 'middle' matrix needs to be shifted for this to
work (#3 above). If you are cheap you can use a middle matrix that is only as
tall as the y height of the thickness of the line is.

> Is there a name or set of terms that characterize this method so I
> could do more research?  I admit to being lost here...

Not that I know of. It is related to scanline raster fill algorythms and
blitting or pattern filling with sprites or textures I think. Maybe someone
else has a better name for this. In general reinventing algorythms is not
productive ... buying a book or two of graphics algorythms may help a lot more
than my message.

Peter P.


2007\10\17@092651 by Peter Bindels

picon face
On 17/10/2007, M. Adam Davis <RemoveMEstienmanKILLspamspam@spam@gmail.com> wrote:
> Unless there's some secret cluster that guarantees each pixel gets
> written exactly once...

Horizontal or vertical line stretched so that the resulting line is as
wide as you want it to be, at an angle of 45-135 degrees to the
direction you want to go. Everytime you skip ahead one line in
bresenham, it moves at most one pixel. Your line will be as wide as
this line is and all pixels will be drawn at most once. Make sure to
scale the width according to the angle of the line (if you go at a 45
degree angle, make it 1.4 times the desired width etc.).

Regards,
Peter

2007\10\17@101815 by M. Adam Davis

face picon face
Excellent suggestion!  I'll have to try this out.  I wonder if I can
extend this to the Wu antialiasing line algorithm...  Seems like it
would essentially be the same.

-Adam

On 10/17/07, Peter Bindels <dascandyspamBeGonespam.....gmail.com> wrote:
{Quote hidden}

> -

2007\10\18@084104 by olin piclist

face picon face
M. Adam Davis wrote:
> But I haven't seen anything about drawing lines of varying width.

There is a lot I could say about this, having designed several commercial
display controllers back when I used to be a graphics guy.  But I'm not
going to do it here.  Post the question on the Microchip forums and send me
a PM to make sure I don't miss it.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\10\18@122924 by M. Adam Davis

face picon face
Thanks for your assistance, Olin.  I sent the PM.

For others interested in following this, apparently mobile, discussion
you can see the thread here:
http://forum.microchip.com/m.aspx?m=289560
Microcontroller Discussion Group >> Tips and Tricks >> Drawing thick lines

I'll probably summarize the outcome here later as well.

-Adam

On 10/18/07, Olin Lathrop <spam_OUTolin_piclistspamKILLspamembedinc.com> wrote:
{Quote hidden}

> -

2007\10\18@141726 by Peter Bindels

picon face
Hello Adam,

Knowing this and having quickly read up on Wu's algorithm, I can be
sure the Wikipedia description is either wrong or the algorithm is.
You need to interpolate the values for three pixels for a one-pixel
wide line for it to be accurate, with increasing error as the slope
goes to 45 degrees.

You determine the cosine of the slope of the line (as in bresenham)
compared to the horizontal or vertical line nearest to where you're
going. You multiply it with the distance in pixels of the pixel you're
drawing compared to the centerpoint you're drawing toward and
determine whether the outcome is within ((line width - 1) / 2). If so,
it's black. If it's larger but below ((line width + 1) / 2),
interpolate the value linearly between these values. If it's larger
than that, it's white.

For getting a "round" starting point you have to extrapolate the "line
width" to match the distance. You would also have to compensate for
that in the starting point line width as the outer most points will
deviate from the "rounded" distance.

Regards, good luck and keep us posted,
Peter

On 17/10/2007, M. Adam Davis <RemoveMEstienmanRemoveMEspamEraseMEgmail.com> wrote:
{Quote hidden}

2007\10\20@052115 by Peter P.

picon face
Olin Lathrop <olin_piclist <at> embedinc.com> writes:
> There is a lot I could say about this, having designed several commercial
> display controllers back when I used to be a graphics guy.  But I'm not
> going to do it here.  Post the question on the Microchip forums and send me
> a PM to make sure I don't miss it.

Why are you hijacking a thread, and why are you proposing the repeated
calculation of the bresenham line for both edges of a thick line ? The equation
must be calculated only once followed by the length of the bit run to fill
across the raster. The Bresenham need not be calculated twice. However, doing it
like this will cause problems in the form of special heuristics to make the
ends, so they end up as needed (chamferred, rounded etc).

To Adam: if you have a 15 bit display and a 32 bit processor it is likely that
you  want to use a plain algorithm. There is not enough room in the word to put
more than one display pixel and its mask.

Peter P.


2007\10\20@082300 by M. Adam Davis

face picon face
On 10/20/07, Peter P. <RemoveMEplpeter2006spamBeGonespamRemoveMEyahoo.com> wrote:
> Why are you hijacking a thread

I'm more than happy to 'travel' for information.  Rather than
hijacking, I tend to think of this as "forking" a thread.  Just
because another thread exists on microchip now doesn't take anything
away from this thread - those who are comfortable here will work with
the thread here, and those more confortable there will work with it
there.  As I'm going to be porting info from there to here then this
thread will actually be better than it would be without the fork.  As
I'm not comfortable at microchip, I won't be porting in that direction
- perhaps someone else will.

So I hope this doesn't become a heavily discussed issue, but if it is
for anyone please fork off a new [OT] thread... :-D

> and why are you proposing the repeated
> calculation of the bresenham line for both edges of a thick line ? The equation
> must be calculated only once followed by the length of the bit run to fill
> across the raster. The Bresenham need not be calculated twice. However, doing it
> like this will cause problems in the form of special heuristics to make the
> ends, so they end up as needed (chamferred, rounded etc).

Yes, I realize that.  Although any line algorithm is going to have
ending special cases.  And yes, bresenham needn't be calculated more
than once.

> To Adam: if you have a 15 bit display and a 32 bit processor it is likely that
> you  want to use a plain algorithm. There is not enough room in the word to put
> more than one display pixel and its mask.

Well the line is going to be a single color/alpha, and the end line
issue makes me think I may have to buffer the output of any good line
drawing algorithm.  Since that's the case it makes sense to pretend
that I have a 1 bit display (320x240, or 2,400 32 bit words).  Would
that give the algorithm you suggest an edge?

-Adam

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2007\10\20@094451 by M. Adam Davis

face picon face
On 10/20/07, Peter P. <KILLspamplpeter2006spamBeGonespamyahoo.com> wrote:
> why are you proposing the repeated calculation of the bresenham line
> for both edges of a thick line?

Re-reading Olin's post, I believe he was suggesting two steps:
Develop a trapezoid renderer (assumes flat top and bottom).
Decompose line into a series of trapezoids.

For a thick line the sides would indeed have the same slope, so
bresenham need be run once.

However, a general trapezoid renderer would require two calculations
(unless the sides have the same slope).

I'm still working my brain through all this, but it seems that such a
method might provide opportunities for nice line ends, which are not
taken care of automatically in a simple duplication of bresenham with
vertical or horizontal lines between.

-Adam

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'[EE] 2D graphics: Drawing thick lines?'
2007\11\20@021416 by M. Adam Davis
face picon face
As a follow up, I've implemented the following algorithm:

http://www.cs.rit.edu/~icss571/filling/index.html

Polygon filling.  It's quite keen!  I really enjoyed learning about
the theory and then implementing it (no code given).  It's a fairly
quick tutorial, so even if you aren't implementing something like this
soon, I suggest going through it just for the fun of it.

I suppose I just ought to go buy a good graphics books one of these days...

-Adam

On Oct 16, 2007 9:21 PM, M. Adam Davis <@spam@stienmanSTOPspamspam@spam@gmail.com> wrote:
{Quote hidden}

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2007\11\20@024614 by Nate Duehr

face
flavicon
face

On Nov 20, 2007, at 12:14 AM, M. Adam Davis wrote:

> As a follow up, I've implemented the following algorithm:
>
> http://www.cs.rit.edu/~icss571/filling/index.html
>
> Polygon filling.  It's quite keen!  I really enjoyed learning about
> the theory and then implementing it (no code given).  It's a fairly
> quick tutorial, so even if you aren't implementing something like this
> soon, I suggest going through it just for the fun of it.

That was kinda fun, and I hate graphics coding.  :-)

I'm by no means up to speed on anything graphics-related... but things  
like this, aren't they typically implemented in hardware these days in  
the high-end graphics cards?  I seem to recall (admittedly  from  
reading up on how various heavy-graphics games work) that the GPU  
handles most of this low-level stuff, like filling polygons, shading  
things on the screen, shadows/other effects... in most cases nowadays.

What I don't know is the "stuff" only a real graphics expert would  
know -- just how much of these features is handled by things like both  
the GPU and the software engines above it like OpenGL and DirectX...  
but I get the impression those layers make it "easy" for the graphics  
coders to ignore these low-level algorithms and implement things.

I wonder if it's like CPU's/microcontrollers though, where an intimate  
knowledge of how to do it by hand can be used (Assembly vs. HLL) to  
really make things fly, if you know what you're doing and have the  
time to implement it by hand.  (Or have the graphics engines out-paced  
the humans, where it would take the humans too long and too many man-
hours to do any of that stuff by hand?)

Wonder if there's any graphics programmers on the list who could  
answer that question simply in terms that the rest of us could  
follow?  :-)

I've always been fascinated by graphics sub-systems, but I really  
disliked writing all the repetitive 'stuff' it took to drive them to  
do anything that looked "neat".  That and I've never had much of an  
imagination for how to make something NEW that looked nice on-screen,  
but I can only recognize the style features that I like... without  
being able to always fully explain them.

--
Nate Duehr
natespamBeGonespamspamBeGonenatetech.com




'[EE] Cutting holes in thick uPVC pipe caps'
2011\02\10@210609 by Philip Pemberton
face
flavicon
face
(EE because "making stuff" is part of engineering :P )

This has been annoying me since about 8PM.

I'm building a case for the night-vision tube using a couple of lengths of PVC pipe. One 90mm dia. length holds the tube proper, and a 50mm-dia. length serves as a spacer to keep the focal-plane distance (distance from the lens to the input coupler) correct. There's a 90mm pipe cap on either end -- one to hold the eyepiece, the other to hold the lens mount and spacer.

What I need to do is knock a ~45mm hole in the front of one of the pipe caps.

Problem 1: these are EXTREMELY thick pipe caps. The plastic walls are about 15mm thick!

Problem 2: I don't have a hole-saw suitable for PVC (actually, I don't have a hole-saw at all: the one in the toolbox has a broken setscrew so the drill bit won't pass any motion onto the saw-blade).

I've tried using the hot-knife bit on an Antex GasCat, which sort-of worked... apart from the fact that it filled my kitchen with acrid smoke and I had to give up part-way through. Turning the heat down only served to completely stop the PVC from melting. Lovely.

The Dremel won't work either -- the router bit gets clogged with bits of PVC very, VERY quickly and just plain stops cutting. I suspect my PCB router bit isn't geared up for uPVC, or the Dremel is moving too fast and melting the plastic (not surprising).

Short of "buy a new holesaw" (apparently *not* stocked by the local B&Q), does anyone have any ideas how I might be able to cut these holes?

Thanks,
-- Phil.
spamBeGonepiclistspamphilpem.me.uk
http://www.philpem.me.uk

2011\02\10@212208 by doug metzler

picon face
maybe a stepped drill bit?

http://www.amazon.com/Neiko-Titanium-Step-Drill-Bit/dp/B000FZ2UOY

It might not solve your 15mm thick problem, though, but it'll do a great job
going through the material.

That said maybe you could use it in some ingenious manner to not only drill
the hole but also step-drill a shelf against which the lens can sit.

DougM

On Thu, Feb 10, 2011 at 6:06 PM, Philip Pemberton <spam_OUTpiclistSTOPspamspamphilpem.me.uk>wrote:

{Quote hidden}

>

2011\02\10@213001 by Mark Rages

face picon face
On Thu, Feb 10, 2011 at 8:06 PM, Philip Pemberton <TakeThisOuTpiclistspamspamRemoveMEphilpem.me.uk> wrote:
> (EE because "making stuff" is part of engineering :P )
> Short of "buy a new holesaw" (apparently *not* stocked by the local
> B&Q), does anyone have any ideas how I might be able to cut these holes?
>

http://www.mini-lathe.com

PVC cuts like butter in a lathe.

Regards,
Mark
-- Mark Rages, Engineer
Midwest Telecine LLC
KILLspammarkragesspamspamspam_OUTmidwesttelecine.co

2011\02\10@213800 by IVP

face picon face

> Problem 1: these are EXTREMELY thick pipe caps. The plastic
> walls are about 15mm thick!

Can you cut it down to 5mm with a hacksaw

2011\02\10@214123 by Marc Nicholas

picon face


Sent from my iPhone
416.414.6271

On 2011-02-10, at 9:22 PM, doug metzler <doug.metzlerRemoveMEspamgmail.com> wrote:

> maybe a stepped drill bit?
>
> www.amazon.com/Neiko-Titanium-Step-Drill-Bit/dp/B000FZ2UOY
>
I bought one of those to cut holes in a 55 gal steel drum. Worked like a champ!

-mar

2011\02\10@214228 by Matt Callow

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On 11 February 2011 13:06, Philip Pemberton <EraseMEpiclistSTOPspamspamRemoveMEphilpem.me.uk> wrote:
{Quote hidden}

How about chain-drilling the hole, then finishing off with a sharp knife?

Mat

2011\02\10@214912 by PICdude

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- You can use the dremel, but keep it well lubricated -- have someone  spray WD-40 on it while you route.

- Get a hole saw (or next smaller size), and cut it, while keeping it  lubricated (as above).

- Lathe.

- CNC mill.

FWIW, making stuff is engineering, but not *electrical* engineering.

Cheers,
-Neil.



Quoting Philip Pemberton <spam_OUTpiclistRemoveMEspamEraseMEphilpem.me.uk>:

{Quote hidden}

>

2011\02\10@223811 by Bob Blick

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On Fri, 11 Feb 2011 02:06 +0000, "Philip Pemberton"  wrote:
> (EE because "making stuff" is part of engineering :P )

Yes! Someone who gets it!

> Short of "buy a new holesaw" (apparently *not* stocked by the local
> B&Q), does anyone have any ideas how I might be able to cut these holes?

Immerse it in a pail of water to keep it cool and then use your dremel
or drill multiple holes in it.

Cheerful regards,

Bob

P.S. don't electrocute yourself in the process!

-- http://www.fastmail.fm - One of many happy users:
 http://www.fastmail.fm/docs/quotes.html

2011\02\10@230730 by jim

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How about buy a large diameter auger bit or spade bit?

Jim

-----Original Message-----
From: EraseMEpiclist-bouncesRemoveMEspammit.edu [spampiclist-bounces.....spamspammit.edu] On Behalf Of
Bob Blick
Sent: Thursday, February 10, 2011 9:38 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Cutting holes in thick uPVC pipe caps

On Fri, 11 Feb 2011 02:06 +0000, "Philip Pemberton"  wrote:
> (EE because "making stuff" is part of engineering :P )

Yes! Someone who gets it!

> Short of "buy a new holesaw" (apparently *not* stocked by the local
> B&Q), does anyone have any ideas how I might be able to cut these holes?

Immerse it in a pail of water to keep it cool and then use your dremel
or drill multiple holes in it.

Cheerful regards,

Bob

P.S. don't electrocute yourself in the process!

-- http://www.fastmail.fm - One of many happy users:
 http://www.fastmail.fm/docs/quotes.html

2011\02\10@230842 by Josh Koffman

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On Thu, Feb 10, 2011 at 10:38 PM, Bob Blick <bobblickspam_OUTspam@spam@ftml.net> wrote:
> Immerse it in a pail of water to keep it cool and then use your dremel
> or drill multiple holes in it.

My machinist often puts certain plastics in the freezer before
engraving or cutting them.

Josh
-- A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
        -Douglas Adams

2011\02\11@030102 by Picbits Sales

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Do you not have a Screwfix near you Philip ?

Its a bit expensive at £40 but its infinitely variable and even clears up after itself ;-)

http://www.screwfix.com/prods/48984/

Dom

{Original Message removed}

2011\02\11@044419 by Philip Pemberton

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On 11/02/11 02:49, PICdude wrote:
> FWIW, making stuff is engineering, but not *electrical* engineering.

And the [EE] tag means "Everything Engineering", not "Electrical Engineering"...

http://www.piclist.com says:
  [EE]: This label is for topics that, while not necessarily about PICs, are of general interest to the engineering community.

Although maybe [TECH] might have been a better choice...

-- Phil.
.....piclistspamspam.....philpem.me.uk
http://www.philpem.me.uk

2011\02\11@045730 by IVP

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> Although maybe [TECH] might have been a better choice...

[TECH] is for stuff you can't do at hom

2011\02\11@065322 by RussellMc

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> > Although maybe [TECH] might have been a better choice...
>
> [TECH] is for stuff you can't do at home

But, he's asking about it BECAUSE he hasn't been able to do it at home ... ;-)

2011\02\11@075543 by Justin Richards

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That is thick plastic.

My 2 cents ...

Jigsaw

Lots of drill holes drilled close together in a circle.

Drill a large hole for a hacksw blade then re-assemble blade into
hacksaw while located in hole drilled in cap.

Fret saw similar to above.

borrow a hydraulic hole punch, these are great fun

Sharpen a socket with angle grinder/bench grinder then use as a punch
with the aid of a vice and a larger socket.  I have often used the
vice with home made punches to press thru thick material.  Have often
used stanley blades to cleanly knife thru thick material with the aid
of a vice.

Chisel and hammer. Might fracture the plastic.
>
> What I need to do is knock a ~45mm hole in the front of one of the pipe
> caps.
>
> Problem 1: these are EXTREMELY thick pipe caps. The plastic walls are
> about 15mm thick

2011\02\11@075735 by John Chung

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Use a drill first. Drill all the way. Then use a round file
to file out the plastic into circle.... Not pretty but it will work
well. You will need a round file and half round ring file.

John



--- On Fri, 2/11/11, Philip Pemberton <piclistKILLspamspamEraseMEphilpem.me.uk> wrote:

{Quote hidden}

> -

2011\02\11@075747 by Justin Richards

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Below may be refereed to as chain-drilling which was previously
offered as an option
>
> Lots of drill holes drilled close together in a circle.

2011\02\11@084047 by Dave Lagzdin

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Melting sounds like a feed rate issue, did you slow down the dremel?

Alternately the outrigger style cutters( as Dom suggested)  in a drill
press set very slow should work
www.acehardware.com/product/index.jsp?productId=1333354
D

On 11 February 2011 03:00, Picbits Sales <RemoveMEsalesKILLspamspamRemoveMEpicbits.co.uk> wrote:
> Do you not have a Screwfix near you Philip ?
> Its a bit expensive at £40 but its infinitely variable and even clears up
> after itself ;-)
> http://www.screwfix.com/prods/48984/
> Dom

2011\02\11@084921 by Carl Denk

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First I would suggest a hole saw, they are inexpensive,  don't require a huge drill to drive it, make a fairly neat hole, and are available in 1/16" (1.6 mm) increments.
2nd, a hand held jigsaw with a blade that is thin enough to allow tight radius cuts.

Both of these are very common, if can't buy, rental or borrowing should be a possibility.

No matter which method, drill briefly and allow material and cutter to cool, and if possible a coolant. If the material melts, a rougher hole happens, and possible to seize tool in hole.

3rd, with dremel, use a 1/8" dia. cutter used to cut wood and drywall like Dremel #560, 561, or Rotozip cutters. Here again material needs to be kept cool. A template that the chuck or smooth part of bit rides on will be helpful, these bits like to wander.

If drilling multiple holes in a circle, start with smaller pilot holes, then using progressively larger bits, say start with 1/8" and stop at 1/4". In plastic, if the drill gets near an adjacent hole, it might try to walk into the next hole, then it gets messy.

On 2/10/2011 11:08 PM, Josh Koffman wrote:
> On Thu, Feb 10, 2011 at 10:38 PM, Bob Blick<TakeThisOuTbobblickspamftml.net>  wrote:
>    
>> Immerse it in a pail of water to keep it cool and then use your dremel
>> or drill multiple holes in it.
>>      
> My machinist often puts certain plastics in the freezer before
> engraving or cutting them.
>
> Josh
>

2011\02\11@090544 by Carl Denk

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Spade might (slight chance) work, but I don't think an auger will. Both of these have fly cutters that score the perimeter, and then with a hand plane (wood) or chisel action, shear the fibers. The plastic doesn't doesn't have the fiber structure. Neither of these will cut decently on end grain wood. Try a wood chisel, to shave off thin slices of the plastic, difficult.

On 2/10/2011 11:07 PM, jim wrote:
> How about buy a large diameter auger bit or spade bit?
>
> Jim
>
> {Original Message removed}

2011\02\11@091842 by Carl Denk

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On 2/10/2011 9:06 PM, Philip Pemberton wrote:
> (
>
> Problem 2: I don't have a hole-saw suitable for PVC (actually, I don't
> have a hole-saw at all: the one in the toolbox has a broken setscrew so
> the drill bit won't pass any motion onto the saw-blade).
>    The hole saw shank should be chucked in the drill, not the drill itself, but to use the drill, grind a flat on the drill for the set screw to clamp on.
>
> The Dremel won't work either -- the router bit gets clogged with bits of
> PVC very, VERY quickly and just plain stops cutting. I suspect my PCB
> router bit isn't geared up for uPVC, or the Dremel is moving too fast
> and melting the plastic (not surprising).
>    Wrong bit, one I suggested has about 1.5" cutting length, the flutes (grooves) are sharpened, and the spiral ejects chips. Try lower speed, maybe using 1/4" electric drill. Speed will melt plastic, and make a mess.
> Short of "buy a new holesaw" (apparently *not* stocked by the local
> B&Q), does anyone have any ideas how I might be able to cut these holes?
>    Borrow, or maybe even pay someone to make the hole. With right tools, it's a 10 minute job. Otherwise could be hours and not a neat job.
> Thanks,
>

2011\02\11@103757 by PICdude

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Quoting Carl Denk <spamBeGonecdenkKILLspamspamTakeThisOuTwindstream.net>:

>> The Dremel won't work either -- the router bit gets clogged with bits of
>> PVC very, VERY quickly and just plain stops cutting. I suspect my PCB
>> router bit isn't geared up for uPVC, or the Dremel is moving too fast
>> and melting the plastic (not surprising).
>>
> Wrong bit, one I suggested has about 1.5" cutting length, the flutes
> (grooves) are sharpened, and the spiral ejects chips. Try lower speed,
> maybe using 1/4" electric drill. Speed will melt plastic, and make a mess..


Will have to disagree with this.  Cutting at almost any speed will  generate enough heat to melt the plastic, as the bit lingers in the  just-cut area.  The way to not melt the plastic is to move out of the  area just cut as quickly as possible, so that means faster feed rate.   And that means faster spindle speed.  Yes, that also means greater  side load on the spindle bearings, so the way to compensate for that  is to take shallower cuts... ie: cut a few mm deep very quickly, then  go around the same path again, but another few mm deep, etc.  This is  fairly standard milling procedure.

If you can make a wooden (or other) template for the spindle  guard-ring to ride on, so it follows the circle, this will make the  whole process MUCH easier.  And keep it cool with WD-40 also.

FWIW, you may want to cut the circle a bit smaller, then file or use a  sanding drum to open it up slowly to the perfect shape/size.

Or if all that fails, just send it to me and I'll CNC-mill it for you.

Cheers,
-Neil.


2011\02\11@111207 by Philip Pemberton

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On 11/02/11 13:49, Carl Denk wrote:
> First I would suggest a hole saw, they are inexpensive,  don't require a
> huge drill to drive it, make a fairly neat hole, and are available in
> 1/16" (1.6 mm) increments.

Well, I picked up two hole-saw kits -- a £10 one from Maplin, and a £15 one from B&Q.

The B&Q one is exactly the same as the "monkey-metal" one I rubbished earlier: a setscrew holding a drill bit in the middle of a metal holder. It sort-of works, but if the saw blade locks up while the drill bit continues spinning, it might (probably will) damage the drill bit.

The Maplin one is a little nicer. The saw blades are solid units -- you pick a blade, attach it to the drill bit via a mounting block, which uses an Allen bolt to hold the drill bit in place. The coupler (which goes into the drill chuck) has a few flat edges, apparently to make it easier for a 3-jaw chuck to grip. Similar idea, but the drill bit is more likely to stick in this case -- but even so, once the drill bit is through, it's not a big deal.

Unfortunately my POS cordless drill decided to play silly devils. The battery won't hold a charge, and because it's a noname POS, you can't get replacements. That'll teach me to buy no-name kit...

Solution: another new toy. A Bosch PSR 18 LI-2. Feels like it was built to hammer nails, fast charge battery, and apparently you can buy everything from case components to the motor, gearbox, switches and the even the speed controller module as a spare part...
Wish I'd bought it from Amazon (about £60 cheaper than B&Q) but I wanted it today, and paid the price... It's still worth £160, IMO.

> No matter which method, drill briefly and allow material and cutter to
> cool, and if possible a coolant. If the material melts, a rougher hole
> happens, and possible to seize tool in hole.

That's pretty much par for the course when cutting/drilling any type of plastic. "Go slowly!"

I still ended up using a set of files to clean up the hole (and the Dremel to cut off a few bits for the lens mount), but it went pretty well. Just need to give the plastic a good clean and apply a bit of black Milliput putty to get rid of a few light leaks.

> 3rd, with dremel, use a 1/8" dia. cutter used to cut wood and drywall
> like Dremel #560, 561, or Rotozip cutters.

I went looking for the Dremel round-cutter while I was at B&Q -- but not a Dremel tool to be seen. Spent a good 15-20 minutes perusing the "electric tools" aisle, to no avail.

> Here again material needs to
> be kept cool. A template that the chuck or smooth part of bit rides on
> will be helpful, these bits like to wander.

In my experience all drill bits like to wander unless you're using a drill press...

Plasterboard bits can usually be persuaded into running straight using a bit of masking tape arranged in an "X" over the desired location, and a small hole (made with a bradawl) in the middle. An automatic centre punch works great on aluminium and other soft metals. It's been a while since I've tried the masking-tape trick on plastic, though IIRC it didn't work too well.

> If drilling multiple holes in a circle, start with smaller pilot holes,
> then using progressively larger bits, say start with 1/8" and stop at
> 1/4". In plastic, if the drill gets near an adjacent hole, it might try
> to walk into the next hole, then it gets messy.

And yet... I didn't think of that. A bunch of 3mm holes joined up with a carbide router bit would have worked pretty well...

(... and it's at this point I start re-reading the "panel building" section of Steve Kasten's book, and all the old EPE "Techniques: Actually Doing It!" columns by R. A. Penfold...)

-- Phil.
EraseMEpiclist.....spamKILLspamphilpem.me.uk
http://www.philpem.me.uk/

2011\02\11@114318 by Carl Denk

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On 2/11/2011 11:12 AM, Philip Pemberton wrote:
{Quote hidden}

http://www.rotozip.com/en-us/Pages/CategoryDetail.aspx?pid=9_8#

{Quote hidden}

>

2011\02\11@115018 by Bob Blick

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On Fri, 11 Feb 2011 09:44 +0000, "Philip Pemberton" wrote:
> On 11/02/11 02:49, PICdude wrote:
> > FWIW, making stuff is engineering, but not *electrical* engineering.
>
> And the [EE] tag means "Everything Engineering", not "Electrical
> Engineering"...
>
> http://www.piclist.com says:
>    [EE]: This label is for topics that, while not necessarily about
> PICs, are of general interest to the engineering community.
>
> Although maybe [TECH] might have been a better choice...

Hi Phil,

piclist.com does not have the official description. The subscription
page has the real one:
http://mailman.mit.edu/mailman/listinfo/piclist

The [EE] topic tag is basically for engineering that you can do
yourself. There is some blend into [TECH] depending on the type of
engineering. In this case it is engineering that someone doing EE is
likely to do at some point, so it fits fine in either EE or TECH.

Cheerful regards,

Bob

-- http://www.fastmail.fm - Choose from over 50 domains or use your own

2011\02\11@115202 by Carl Denk

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On 2/11/2011 10:37 AM, PICdude wrote:
{Quote hidden}

>

'[EE] Cutting holes in thick uPVC pipe caps -rebuil'
2011\02\11@115941 by Carl Denk

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>
>> Unfortunately my POS cordless drill decided to play silly devils. The
>> battery won't hold a charge, and because it's a noname POS, you can't
>> get replacements. That'll teach me to buy no-name kit...
>>      I have used these people numerous time to rebuild batteries with good results. But you would have to check with them if your particular model is rebuildable. :)

http://www.primecell.com/howto.ht

2011\02\11@121612 by Philip Pemberton

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On 11/02/11 16:43, Carl Denk wrote:
>> The B&Q one is exactly the same as the "monkey-metal" one I rubbished
>> earlier: a setscrew holding a drill bit in the middle of a metal holder.
>> It sort-of works, but if the saw blade locks up while the drill bit
>> continues spinning, it might (probably will) damage the drill bit.
>>
> Gripping the drill bit, and relying on the bit to turn the hole saw, is
> only for very light work at best.

As I found out... The drill bit tended to slip in the chuck (it's covered in silver marks where the chuck jaws have spun around the bit). Hopefully it didn't damage the chuck...

> Yep that's what the flats are for, the quality drill bits, larger than
> 3/16" that I buy at the local independent tool store, all have the
> flats.

It's pretty rare to see drill bits with a flattened shank around here. The vast majority are round -- even the PCB drills.

> I always buy name brand that there are local repair stations for parts.
> Long term well worth it. A lot better than at most inopportune time,
> having to go chase tools.

Oh, too right. Before I got the Dremel, I used to drill PCBs with an Expo Reliant "mini-drill". That was an exercise in futility. The 3-jaw chuck wasn't mounted straight on the motor shaft, so the bit moved to either side. Broke most of my tungsten bits before I figured out what was going on.

>> Wish I'd bought it from Amazon (about £60 cheaper than B&Q) but I wanted
>> it today, and paid the price... It's still worth £160, IMO.
>>
> Could be counterfeit.

Point taken. I did notice that even the likes of Axminster Tools were only selling them at ~£150 (per Google Shopper) so £169 isn't too bad a price.

Yes, it's complete, yes it works, yes it's the "genuine article" (at least as far as I can tell!).

> I have on order a set of Rayban sunglasses, as
> hard a I try, I am quite sure they are counterfeit, if they arrive at
> all. The Seattle address is for the main Seattle newspaper, and they
> have concurred that they don't have an address there. :(

LOL! So the scammers used the address of a major newspaper in Seattle?
IME, they usually use addresses which just plain don't exist...

> Check out these Rotozip
> http://www.rotozip.com/en-us/Pages/CategoryDetail.aspx?pid=9_8#

I don't think I've ever seen a Rotozip tool in any of the local shops... they seem a bit thin on the ground outside of the USA...

> If you have a router, that should work if you make a jig to hold the
> work and guide the router.

I don't have a router -- what I have are a couple of 2mm tungsten-carbide PCB router bits which just happen to fit the Dremel.

> Sometimes I have spent much more time
> building a jig/guide that actual cutting, but end up with a neat hole.
> Just last night was watching a woodworking show on the TV, the whole
> show was on router jigs. :)

I wish we had shows like that on TV... closest we get to that is "Changing Rooms" or "Grand Designs". Neither of which is even remotely interesting...

And then there's X Factor and American Idol... I wish ITV would just give up on those shows, they really are atrocious. Lowest-common-denominator tripe at its very worst.

(though as long as Auntie Beeb retain some semblance of integrity, the TV license will continue to be paid... ITV could disappear entirely, and I'm not entirely sure I'd be able to give half a tweet, much less an entire hoot!)

-- Phil.
piclistSTOPspamspamphilpem.me.uk
http://www.philpem.me.uk/

2011\02\11@122229 by Walter Banks

picon face
Use a forstner bit. $10-$15 use water or alcohol as a coolant. This will
make very clean holes. I have used them on PVC caps for telescope
parts.


Regards,


w..
--
Walter Banks
Byte Craft Limited
http://www.bytecraft.com



2011\02\11@124107 by Carl Denk

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> The drill bit tended to slip in the chuck (it's covered in silver marks where the chuck jaws have spun around the bit).
> Hopefully it didn't damage the chuck...
>    Not likely to damage the chuck, just tears up the drill shank. Clean it up with a fine file.
>    
>
> It's pretty rare to see drill bits with a flattened shank around here.
> The vast majority are round -- even the PCB drills.
>    These are good quality industrial production machinery quality, but not that much more money.
>    
>> I always buy name brand that there are local repair stations for parts.
>> Long term well worth it. A lot better than at most inopportune time,
>> having to go chase tools.
>>      
>
> I don't think I've ever seen a Rotozip tool in any of the local shops...
> they seem a bit thin on the ground outside of the USA...
>    And on Walter's suggestion of Forstener bits, will have to try that, wouldn't have expected that to work. :)

What I saw those Dremel bits were very similar to the wood/plastic bits.
>    
>
> I wish we had shows like that on TV... closest we get to that is
> "Changing Rooms" or "Grand Designs". Neither of which is even remotely
> interesting...
>    We have Directv satelite, and there is a large variety available including a wide variety of Do it programs. :)
> And then there's X Factor and American Idol... I wish ITV would just
> give up on those shows, they really are atrocious.
> Lowest-common-denominator tripe at its very worst.
>    The local Fox TV channel news always is promoting "Idol", when I  hear that word, it's to a different channel

2011\02\11@124243 by Gary Crowell

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Just a comment, and I don't mean to sound pretentious or arrogant, or
anything; and I know it's not possible for everyone.  But, I think about the
hundreds of hours I've spent over the past 40 years flailing away at bits of
metal and plastic with files, hacksaws and various implements of
destruction...  and I can't believe I didn't buy a mill and lathe sooner.

Gary
----------------------------------------------
Gary A. Crowell Sr., P.E., CID+
Linkedin <http://www.linkedin.com/in/garyacrowellsr>
Elance<www.linkedin.com/redirect?url=http%3A%2F%2Fgaryacrowellsr%2Eelance%2Ecom&urlhash=kJm9>
 KE7FIZ <http://www.arrl.org

2011\02\11@133849 by Walter Banks

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Carl Denk wrote:

> And on Walter's suggestion of Forstener bits, will have to try that,
> wouldn't have expected that to work. :)
>
>

The trick with any cutting of plastic is to keep the bit cool. There have been
suggestions to pre freeze. I have done that works but a better way is to use
coolant to keep the plastic below its melting point as it being cut. Plastic is
an insulator and doesn't conduct heat very well so the bit needs to be cooled.
Alcohol is a good coolant because of its low boiling point. Water will work
quite well but needs more care. It the plastic starts to stick to the bit it isn't
cool enough.

For plastic caps that I have drilled I have usually used a mill or drill press
at relatively low speed.

w..

2011\02\11@144649 by William \Chops\ Westfield

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On Feb 11, 2011, at 10:38 AM, Walter Banks wrote:

> Alcohol is a good coolant because of its low boiling point.

Alcohol would make me very nervous, given the sparks I see the average  drill motor make.

BillW

2011\02\11@163322 by PICdude

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WD-40 and automatic transmission fluid make pretty decent coolants.


Quoting "William \"Chops\" Westfield" <westfwSTOPspamspamKILLspammac.com>:

>
> On Feb 11, 2011, at 10:38 AM, Walter Banks wrote:
>
>> Alcohol is a good coolant because of its low boiling point.
>
> Alcohol would make me very nervous, given the sparks I see the average
> drill motor make.
>
> BillW
>
>

2011\02\11@170354 by Walter Banks

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PICdude wrote:

{Quote hidden}

It is always alcohol and water. I have never had a coolant
ignite. WD-40 will work well

w..

2011\02\14@093748 by Michael Rigby-Jones

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> -----Original Message-----
> From: spampiclist-bounces.....spam.....mit.edu [piclist-bounces.....spammit.edu] On
Behalf
{Quote hidden}

have
> been
> suggestions to pre freeze. I have done that works but a better way is
to
> use
> coolant to keep the plastic below its melting point as it being cut.
> Plastic is
> an insulator and doesn't conduct heat very well so the bit needs to be
> cooled.
> Alcohol is a good coolant because of its low boiling point. Water will
> work
> quite well but needs more care. It the plastic starts to stick to the
bit
> it isn't
> cool enough.
>
> For plastic caps that I have drilled I have usually used a mill or
drill
> press
> at relatively low speed.

I've even managed to use the "spade" bits designed for boring holes into
wood with great success on soft plastics like PVC.

Mike

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'[EE] Shielding sensitive eletronics: is thickness '
2011\11\06@100304 by Electron
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Hello,
when shielding sensitive eletronics is the thickness of the metal shield important?

As I'm gonna pot my small circuit into epoxy, I'm tempted to use cheap aluminium
foil to shield the circuit (which seems necessary since I increased the clock
speed (PLLx16), and the environment is disturbed, at 1/16s speed it never crashed
although all the EMI).

Greets,
Mario

2011\11\06@115525 by Sean Breheny

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Hi Mario,

I believe that the thickness does matter to some degree. Also, it
greatly depends on what you are trying to do - prevent radiation FROM
your device, protect your device from external EM radiation, protect
your device from external low-frequency fields, etc. Can you describe
your application further?

Shielding is a tough subject - it is difficult to get it right the
first time. I would suggest that you get your circuit working
properly, including the shielding aspects, before you pot it.

Sean


On Sun, Nov 6, 2011 at 10:02 AM, Electron <KILLspamelectron2k4spam_OUTspaminfinito.it> wrote:
{Quote hidden}

>

2011\11\06@121504 by David VanHorn

picon face
On Sun, Nov 6, 2011 at 8:02 AM, Electron <spam_OUTelectron2k4spamTakeThisOuTinfinito.it> wrote:
>
> Hello,
> when shielding sensitive eletronics is the thickness of the metal shield important?


Thickness helps with low frequency magnetics. A good resource for this
would be any of the vendors of Mu-Metal.
They have application notes that discuss where Mu-Metal works, and
where copper/aluminum works, and how thickness impacts things.


I would look for other sources for your problem though.. From what
little you've said, it sounds more like a PLL stability problem

2011\11\06@125015 by Yigit Turgut

picon face
That all depends on the structure you want to protect as well as the
dispersion parameters of the foil you use. When you cover it with
aluminium  foil you simply cover it with a Faraday cage where grid
mesh size goes to limit 0. Thickness will be a problem if you are
running high frequency components in your circuit due to skin effect
(not penetration depth). If frequency of the core is 16 times the
peripherials, it would be an unexpected behavior if one/some of the
peripherials malfunction where core operates flawlessly. Because high
frequency components will be more prone to environmental effects. It
ends up evaluating the operation environment of your gadget. I have
encountered cases where the device works %100 at a location and goes
crazy at another location due to magnetic and electric field
components of those specific locations - even it was shielded. It is
NOT about the amplitude of the EM around -directly-, it is about the
vectoral components of the disturbing field/wave.

Model the structure and expose to random(vector) far fields then you
can extract em response of your system. It is also even possible to
determine the electrical level effects of the environmental em
radiation in your circuit via more advanced approaches.

It all ends up in the digits of your budget (:

On Sun, Nov 6, 2011 at 5:02 PM, Electron <.....electron2k4.....spamRemoveMEinfinito.it> wrote:
{Quote hidden}

>

2011\11\06@125605 by Mark Hanchey

flavicon
face
On 11/6/2011 12:15 PM, David VanHorn wrote:
> On Sun, Nov 6, 2011 at 8:02 AM, Electron<spam_OUTelectron2k4TakeThisOuTspamEraseMEinfinito.it>  wrote:
>> Hello,
>> when shielding sensitive eletronics is the thickness of the metal shield important?
>
> Thickness helps with low frequency magnetics. A good resource for this
> would be any of the vendors of Mu-Metal.
> They have application notes that discuss where Mu-Metal works, and
> where copper/aluminum works, and how thickness impacts things.
>
>
> I would look for other sources for your problem though.. From what
> little you've said, it sounds more like a PLL stability problem.

speaking of Mu-Metal I saw this while browsing the other day. $10 for a sheet of it.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16600A

Not sure if that is low or high, but seemed an okay price.
Mark

2011\11\06@152601 by Electron

flavicon
face

Dear Sean,
I need to protect my application from the external environment, namely
from the interference caused by a spark plug. It's a motorbike application.

The spark at the oscilloscope looks like an impulse with 1uS rising edge
and 20-25uS falling edge.

With kind regards,
Mario


At 17.55 2011.11.06, you wrote:
{Quote hidden}

>> -

2011\11\06@152601 by Electron

flavicon
face
At 18.15 2011.11.06, you wrote:
>On Sun, Nov 6, 2011 at 8:02 AM, Electron <RemoveMEelectron2k4spamBeGonespamspaminfinito.it> wrote:
>>
>> Hello,
>> when shielding sensitive eletronics is the thickness of the metal
>shield important?
>
>
>Thickness helps with low frequency magnetics. A good resource for this
>would be any of the vendors of Mu-Metal.
>They have application notes that discuss where Mu-Metal works, and
>where copper/aluminum works, and how thickness impacts things.
>
>
>I would look for other sources for your problem though.. From what
>little you've said, it sounds more like a PLL stability problem.

Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
crystal in XT mode and and PLLx16. The part can reach 30 MHz.

Cheers,
Mario

2011\11\06@215221 by Sergey Dryga

flavicon
face
Electron <electron2k4 <at> infinito.it> writes:

> Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
> crystal in XT mode and and PLLx16. The part can reach 30 MHz.

Without knowing what part you are using, your crystal frequency X 16 >>>> 30
MHz.  Unless the crystal is divided before PLL, that would be a problem.  
Sergey Dyrga
http://beaglerobotics.com


2011\11\07@133820 by Electron

flavicon
face
At 03.52 2011.11.07, you wrote:
>Electron <electron2k4 <at> infinito.it> writes:
>
>> Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
>> crystal in XT mode and and PLLx16. The part can reach 30 MHz.
>
>Without knowing what part you are using, your crystal frequency X 16 >>>> 30
>MHz.  Unless the crystal is divided before PLL, that would be a problem.  
This is a dsPIC30F2011, very basic PLL (x4 or x8 or x16)

Greets,
Mario

2011\11\07@143348 by Isaac Marino Bavaresco

flavicon
face
Em 7/11/2011 15:18, Electron escreveu:
> At 03.52 2011.11.07, you wrote:
>> Electron <electron2k4 <at> infinito.it> writes:
>>
>>> Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
>>> crystal in XT mode and and PLLx16. The part can reach 30 MHz.
>> Without knowing what part you are using, your crystal frequency X 16 >>>> 30
>> MHz.  Unless the crystal is divided before PLL, that would be a problem.  
> This is a dsPIC30F2011, very basic PLL (x4 or x8 or x16)


Beware, many PLLs accept the input frequency only in a very narrow band
(say, 4MHz to 8MHz).
If your crystal frequency divided by the input divider is outside this
range, the PLL may not work.


Isaac

2011\11\07@155614 by David VanHorn

picon face
> Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
> crystal in XT mode and and PLLx16. The part can reach 30 MHz.


PLL circuits can be very interesting to get working properly, under
all conditions.
If you are taking a 7.3728 Mhz clock and multiplying by 16, then you
are trying to run the part at 118 MHz, which seems like it's going to
be a problem. :)

What I would do:

First, get the basic system up on direct crystal oscillator, and
provide an output pin that indicates clock speed by using a timer or
pin toggle, or whatever you can easily diagnose with the tools at
hand.

Then read very carefully the PLL section of the data sheet, including
the step-by-step sequence to transition from the crystal to the PLL.
Implement per data sheet with NO shortcuts.  You may need to implement
an analog PLL filter depending on the particular part you're using.

Verify that the system is now running correctly at the proper speed.


Given that you're working in an automotive environment, are you using
regulation and bypassing designed for this?

Don't look for complicated problems when you have simple ones. :

2011\11\08@024825 by Electron

flavicon
face
At 20.03 2011.11.07, you wrote:
>Em 7/11/2011 15:18, Electron escreveu:
>> At 03.52 2011.11.07, you wrote:
>>> Electron <electron2k4 <at> infinito.it> writes:
>>>
>>>> Thank you. How can I investigate if it's a PLL issue? I'm using a
>7.3728 MHz
>>>> crystal in XT mode and and PLLx16. The part can reach 30 MHz.
>>> Without knowing what part you are using, your crystal frequency X 16 >>>> 30
>>> MHz.  Unless the crystal is divided before PLL, that would be a problem..  
>> This is a dsPIC30F2011, very basic PLL (x4 or x8 or x16)
>
>
>Beware, many PLLs accept the input frequency only in a very narrow band
>(say, 4MHz to 8MHz).
>If your crystal frequency divided by the input divider is outside this
>range, the PLL may not work.

Thank you, but this is not the case, I had checked the errata too to make sure
(indeed there're even bugs on the PLL, but only for 4x and 8x modes, while I'm
using the 16x mode).

A futher examination of the errata made me get doubts about this though, do you
think it could be the cause?

---

15. Module: PLL Lock Status Bit

The PLL LOCK Status bit (OSCCON<5>) can occasionally get cleared and generate an
oscillator failure trap even when the PLL is still locked and functioning correctly.

Work around: The user application must include an oscillator failure trap service
routine. In the trap service routine, first inspect the status of the Clock Failure
Status bit (OSCCON<3>). If this bit is clear, return from the trap service routine
immediately and continue program execution.

---

Unfortunately my app is strictly real-time and I cannot enable any interrupt. But
is this possibly causing the malfunction at near full speed?

Greets,
Mario

2011\11\08@035316 by Electron

flavicon
face
At 21.56 2011.11.07, you wrote:
>> Thank you. How can I investigate if it's a PLL issue? I'm using a 7.3728 MHz
>> crystal in XT mode and and PLLx16. The part can reach 30 MHz.
>
>
>PLL circuits can be very interesting to get working properly, under
>all conditions.
>If you are taking a 7.3728 Mhz clock and multiplying by 16, then you
>are trying to run the part at 118 MHz, which seems like it's going to
>be a problem. :)

It's within specs, the dsPIC30F2011-30 can run up to 120 MHz, the system
clock (Fcy) runs at only 1/4 of that frequency (i.e. 29.4912 MHz). :-)


{Quote hidden}

Well, yes, but currently it's on my bench, not on the vehicle. However,
when I generate sparks (I got the coil and all on my bench, it's a CDI
that I'm designing) then every n (random) seconds the MPU crashes. If
instead of the spark I use a resistor (~same discharge current of the
coil) then no problems arise, hence I thought it was an EMI problem.


>Don't look for complicated problems when you have simple ones. :)

I don't wish to complicate my life, don't worry. :-) Just to make things
reliable, as I'll race on the woods with my CDI, and a failure is gonna
cause me some problems. I may not become the enduro world champion for
example. :P

:D

2011\11\08@040140 by alan.b.pearce

face picon face
> Without knowing what part you are using, your crystal frequency X 16 >>>> 30 MHz.
> Unless the crystal is divided before PLL, that would be a problem.

The datasheet does say that you can use XT crystal mode with x16 PLL, and crystals over the range of 4 - 7.5MHz, provided the maximum operating frequency of 120MHz is met (ref table 17-1 of the Rev C data sheet). So he is within the operating parameters of the PLL.
-- Scanned by iCritical.

2011\11\08@131528 by David VanHorn

picon face
> Well, yes, but currently it's on my bench, not on the vehicle. However,
> when I generate sparks (I got the coil and all on my bench, it's a CDI
> that I'm designing) then every n (random) seconds the MPU crashes. If
> instead of the spark I use a resistor (~same discharge current of the
> coil) then no problems arise, hence I thought it was an EMI problem.


So now you're down to impedance, decoupling and layout issues.
Have you checked your design to see that all circuits are built with
the lowest practical impedance?
Decoupling can be critical. 0.1uF is not always the best value.

Build a noise probe, using a relay wired as a buzzer and a series LC
across the contacts, with the L being a small (pencil-eraser sized)
coil.  Use this to probe for weak points and evaluate.  Change design
as needed

2011\11\08@184811 by Chris Roper

picon face
> Build a noise probe, using a relay wired as a buzzer and a series LC
> across the contacts, with the L being a small (pencil-eraser sized)
> coil.  Use this to probe for weak points and evaluate.  Change design
> as needed.

Any schematics for a noise probe out there?
It sounds interesting, but I have never heard of one before,  I am
used to working with off the shelf hardware, but we are at the stage
where we need our own boards. The current design has been farmed out
to a hardware house, but it would be great to build up my own test
bench so I can QC their QC.

2011\11\09@054118 by Electron

flavicon
face
At 00.48 2011.11.09, you wrote:
>> Build a noise probe, using a relay wired as a buzzer and a series LC
>> across the contacts, with the L being a small (pencil-eraser sized)
>> coil.  Use this to probe for weak points and evaluate.  Change design
>> as needed.

Thanks, but I'm not sure I understand the implementation, nor if this
noise probe should detect EMI or should be connected to various points
in the circuit.

2011\11\09@093027 by David VanHorn

picon face
The noise probe is a small localized source of magnetic noise.

When the contacts open on the buzzer-relay, the coil inductance has
some fair energy stored that MUST go somewhere.  The series RC network
that is the probe itself provides a convenient place.   If you build
it, you can take a thruhole LED, short its leads and bend them into a
hoop, and light the LED from energy radiated up to about an inch away.

I'll try to post a schematic today

2011\11\09@134056 by Electron

flavicon
face
At 15.30 2011.11.09, you wrote:
>The noise probe is a small localized source of magnetic noise.
>
>When the contacts open on the buzzer-relay, the coil inductance has
>some fair energy stored that MUST go somewhere.  The series RC network
>that is the probe itself provides a convenient place.   If you build
>it, you can take a thruhole LED, short its leads and bend them into a
>hoop, and light the LED from energy radiated up to about an inch away.
>
>I'll try to post a schematic today.

Interesting, thanks.

So the purpose of the noise probe (on my circuit at least) would be to
deliberately cause interference, i.e. to test the reliability of my circuit?

2011\11\09@153841 by David VanHorn

picon face
> So the purpose of the noise probe (on my circuit at least) would be to
> deliberately cause interference, i.e. to test the reliability of my circuit?


Yes.  The small probe coil allows you to do this in a targeted manner.
Alternatively, you can spend some serious bucks illuminating your PCB
in a chamber at various frequencies.

I have a PDF that I can email you directly, but I don't have a way to
post it anywhere convenient

2011\11\10@065940 by Electron

flavicon
face
At 21.38 2011.11.09, you wrote:
>> So the purpose of the noise probe (on my circuit at least) would be to
>> deliberately cause interference, i.e. to test the reliability of my circuit?
>
>
>Yes.  The small probe coil allows you to do this in a targeted manner.
>Alternatively, you can spend some serious bucks illuminating your PCB
>in a chamber at various frequencies.
>
>I have a PDF that I can email you directly, but I don't have a way to
>post it anywhere convenient.

Megaupload maybe? I don't know any other free hosting sites.

Meanwhile, thank You for the eMail.. please feel free to send it! :-)

Cheers,
Mario


'[EE] Looking for potentiometers for thick panels'
2012\10\23@172453 by Neil
flavicon
face
Hi all,

Can anyone recommend a panel-mount potentiometer that I can use on 1/4" thick wood?  Most of the ones I'm finding seem to have 5mm - 6.5mm threaded sections, and factoring in the thickness of the nut and washer, that leaves a max panel thickness of only ~0.080". Ideal would be to avoid countersinking, but if I need to it's fine. It's just that 0.080" is really think for MDF.  Anywhere from 5k to 50k is fine, linear taper.  I need ~30 of these, so lower cost preferred.

Cheers,
-Neil.

2012\10\23@173519 by William Bross

picon face
Neil,

Instead of special pots, do you have enough room behind the panel for an aluminum U bracket to mount the pots and shaft extensions on the pots?  That got me out of a bind on some custom stuff rather inexpensively in the past.

Bill

Neil wrote:

{Quote hidden}

>

2012\10\23@180520 by Dave

picon face
That is usually handled using a sub panel and projecting the shafts thru the front panel.

Neil <@spam@picdude3spamspamnarwani.org> wrote:

{Quote hidden}

>

2012\10\23@180829 by Neil

flavicon
face
Exactly what we were thinking, but I'm trying to avoid the fabrication if I can.  This is part of a display, and there's too much else to do currently.  A simple barrel nut would work well to pick up the thickness difference, but these pots seem to use non-standard M8 x 0.75 threads. :(


On 10/23/2012 5:35 PM, William Bross wrote:
{Quote hidden}

>>

2012\10\23@181603 by IVP

face picon face
> Ideal would be to avoid countersinking

Can you route the back ? It's what I do with 9 and 12mm MDF.
A trench with rounded corners looks OK on the front too, becomes
part of the design and highlights the pots. Failing that, drill holes for
the shafts and mount the pots on metal sheet screwed to the wood

Jo

2012\10\23@181620 by Neil

flavicon
face
You mean a thin layer of some other sheeting?  Avoiding that too.  Epoxy is looking so tempting right now.


On 10/23/2012 6:05 PM, Dave wrote:
{Quote hidden}

>> --

2012\10\23@182940 by Neil

flavicon
face
Originally, we had intended to countersink the back using a square-end milling cutter.  The nuts/washers on the front would be on the actual front face. However, the 0.080" remaining thickness worries me.  It's for a trade-show display and needs to be strong.  We'll be laying adhesive vinyl over the top, so any brackets etc need to be hidden under the knob, else the height differences would be visible under the vinyl.  And we want to use small-diameter knobs.

I like the idea of sheet metal, but on the *back* of the wood, assuming I can find pots with longer shafts.  If that's what you meant, then thank you.  If not, then thank me :)

Cheers,
-Neil.


On 10/23/2012 6:15 PM, IVP wrote:
>> Ideal would be to avoid countersinking
> Can you route the back ? It's what I do with 9 and 12mm MDF.
> A trench with rounded corners looks OK on the front too, becomes
> part of the design and highlights the pots. Failing that, drill holes for
> the shafts and mount the pots on metal sheet screwed to the wood
>
> Joe

2012\10\23@184045 by IVP

face picon face
> Epoxy is looking so tempting right now

Don't know if I'd trust epoxy on its own with a moving part, ie
there will be some stress when the pot is turned and stops at the
extremes. MDF isn't very strong mechanically, it would be the
weakest link in this mounting, and it's easy to pull off the top layer.
Using the pot case tab will help

I might try a slightly under-size hole and either tap it or thread it
with the pot

Jo

2012\10\23@184939 by IVP

face picon face

> I like the idea of sheet metal, but on the *back* of the wood,
> assuming I can find pots with longer shafts.  If that's what you
> meant, then thank you.  If not, then thank me :)

Hey, thanks all round, they're free right ? Everybody, dig in

Yes, I did mean a metal plate on the inside of the case (for
appearances' sake as much as anything), and assumed you
had pots with longish shafts, at least 20mm anyway

My local retail store has a surprisingly good variety of 9, 16
and 24mm for PCB and panel mount, all with long shafts
(although the 9mm are more common with short fluted shafts),
so it shouldn't be too hard to find what you want

Jo

2012\10\23@201837 by Perry Curling-Hope

picon face
If minimum fabrication time / effort is the primary objective, you may like
to substitute thin ABS plastic sheet for sheetmetal,
Such is easily and quickly worked with rudimentary tools, i,e, a box cutter
and steel rule and a cordless drill.

The backplates can be scored and snapped apart from the stock sheet in
seconds, and cun be held in position on the back of the wood and the whole
thing drilled one time  while in place ensuring perfect alignment for small
woodscrews and plastic spacers (which obviates the need to counterbore the
woodl) to fasten the panel

On Wed, Oct 24, 2012 at 12:49 AM, IVP <.....joecolquittRemoveMEspamclear.net.nz> wrote:

{Quote hidden}

>

2012\10\23@215147 by Dave Tweed

face
flavicon
face
Neil wrote:
> Originally, we had intended to countersink the back using a square-end
> milling cutter.  The nuts/washers on the front would be on the actual
> front face. However, the 0.080" remaining thickness worries me.  It's
> for a trade-show display and needs to be strong.  We'll be laying
> adhesive vinyl over the top, so any brackets etc need to be hidden under
> the knob, else the height differences would be visible under the vinyl.  
> And we want to use small-diameter knobs.
>
> I like the idea of sheet metal, but on the *back* of the wood, assuming
> I can find pots with longer shafts.  If that's what you meant, then
> thank you.  If not, then thank me :)

Go with that ... with or without routing from the back to reduce the overall
thickness, and with or without drilling the holes in the wood oversize to
accomodate the nuts (and a nutdriver).

-- Dave Twee

2012\10\24@044826 by alan.b.pearce

face picon face
> The backplates can be scored and snapped apart from the stock sheet in seconds, and
> cun be held in position on the back of the wood and the whole thing drilled one time
> while in place ensuring perfect alignment for small woodscrews and plastic spacers
> (which obviates the need to counterbore the
> woodl) to fasten the panel

I suspect he may want to counter bore the back of the wood to take the threaded boss and nut, so there is only a small hole in the front of the wood, clearance size for the shaft (plus a small positioning tolerance). Otherwise he needs a boss sized hole right through the wood with a shallow countersink to take the nut, or the metal panel is spaced back from the wood by the thickness of the nut.


-- Scanned by iCritical.

2012\10\24@111248 by John Ferrell

face
flavicon
face
Think about mounting with a T-Nut and improvise a shaft extension...

On 10/24/2012 4:46 AM, KILLspamalan.b.pearcespamTakeThisOuTstfc.ac.uk wrote:
>> The backplates can be scored and snapped apart from the stock sheet in seconds, and
>> cun be held in position on the back of the wood and the whole thing drilled one time
>> while in place ensuring perfect alignment for small woodscrews and plastic spacers
>> (which obviates the need to counterbore the
>> woodl) to fasten the panel
> I suspect he may want to counter bore the back of the wood to take the threaded boss and nut, so there is only a small hole in the front of the wood, clearance size for the shaft (plus a small positioning tolerance). Otherwise he needs a boss sized hole right through the wood with a shallow countersink to take the nut, or the metal panel is spaced back from the wood by the thickness of the nut.
>
>

-- John Ferrell W8CCW
“During times of universal deceit,
  Telling the TRUTH becomes a revolutionary act”
     George Orwell

2012\10\24@113635 by Neil

flavicon
face
part 1 1168 bytes content-type:text/plain; charset="Windows-1252" (decoded quoted-printable)

Could not find t-nuts to match the pot threads, so this is what we ended up with... (attached).  This is pretty simple.



On 10/24/2012 11:12 AM, John Ferrell wrote:
{Quote hidden}


part 2 15786 bytes content-type:image/jpeg; name="Pot-mounting-01.jpg" (decode)


part 3 181 bytes content-type:text/plain; name="ATT00001.txt"
(decoded base64)

--
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2012\10\24@114323 by alan.b.pearce

face picon face
> Think about mounting with a T-Nut and improvise a shaft extension...

He said earlier that they have 'non-standard 8 x 0.75 threads' and I don't know if they make T-nuts with M8x0.75 threads. The chart I looked at lists that as a fine thread, and I suspect the normal one is M8x1, although that is also listed as fine, and M8x1.25 is listed as coarse!

I suspect looking at the T-Nuts I have that such things are normally made with the coarse thread for the thread size.

-- Scanned by iCritical.

2012\10\24@131140 by Eoin Ross

flavicon
face
Would drilling and tapping an M6 one be feasible?

On 10/24/2012 11:42 AM, RemoveMEalan.b.pearcespamspamSTOPspamstfc.ac.uk wrote:
>> Think about mounting with a T-Nut and improvise a shaft extension...
> He said earlier that they have 'non-standard 8 x 0.75 threads' and I don't know if they make T-nuts with M8x0.75 threads. The chart I looked at lists that as a fine thread, and I suspect the normal one is M8x1, although that is also listed as fine, and M8x1.25 is listed as coarse!
>
> I suspect looking at the T-Nuts I have that such things are normally made with the coarse thread for the thread size.
>

2012\10\24@134054 by John Ferrell

face
flavicon
face
Mechanical issues can sure be a challenge sometimes.
I would think if you just had loose fit on the threads a few chips of hot melt glue and heat with a soldering tool would make reasonably sturdy mount. The problem with using really tough adhesives like JB Weld is that it is impossible to take apart without damages.
I would not hesitate to cross thread a component into a t-nut if it would do the job!

On 10/24/2012 11:42 AM, .....alan.b.pearceEraseMEspamstfc.ac.uk wrote:
>> Think about mounting with a T-Nut and improvise a shaft extension...
> He said earlier that they have 'non-standard 8 x 0.75 threads' and I don't know if they make T-nuts with M8x0.75 threads. The chart I looked at lists that as a fine thread, and I suspect the normal one is M8x1, although that is also listed as fine, and M8x1.25 is listed as coarse!
>
> I suspect looking at the T-Nuts I have that such things are normally made with the coarse thread for the thread size.
>

-- John Ferrell W8CCW
“During times of universal deceit,
  Telling the TRUTH becomes a revolutionary act”
     George Orwell


'[OT] MEASURE ICE THICKNESS FROM TOP'
2013\11\06@200603 by BOB
picon face
I have a friend who is a die hard ice fisherman.  He was wondering if there is a way to measure the thickness of ice on a lake with out drilling a hole in it.

Anyone know of some type of sensor that would do this?

Bob
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2013\11\06@202606 by Robert Rolf

picon face
Ultrasound. Commercial thickness gauges for steel cover a few inches.
Don't know about ice.
Some experts can tell from sledge hammer thump on top.


On Wed, Nov 6, 2013 at 6:06 PM, BOB <spamBeGonebobscncspamRemoveMEcharter.net> wrote:
{Quote hidden}

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2013\11\06@202935 by Robert Rolf

picon face
Contactless Ice thickness meter
http://uwbs.ru/en/products/izmeritel-tolschiny-lda-picor-ice/

http://www.beckerarena.com/UserFiles/File/Library/Ice%20Tec%208%20Manual.pdf

and plenty more with google search

On Wed, Nov 6, 2013 at 6:26 PM, Robert Rolf <.....Robert.RolfEraseMEspamualberta.ca> wrote:
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2013\11\06@224509 by BOB

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After much reading I think a robot with a drill attachment.
as you apply down pressure the robot front lifts. Start the drill. When the robot drops the drill is through the ice.  Take a measurement and move on.

With a small GPS unit and a radio link you could map out a body of water or ice.

Something to think about for when I have too much time on my hands.

Bob
On 11/6/2013 7:29 PM, Robert Rolf wrote:
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2013\11\06@234039 by Jean-Paul Louis

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Or you could try an ultrasonic Doppler sensor (car back-up device). The interface ice water will cause a reflection, so you can deduct ice thickness.
 
Good luck,

Jean-Paul
AC9GH


"Democracy is two wolves and a lamb deciding what to have for dinner. Liberty is a well-armed lamb."     - Benjamin Franklin -



On Wednesday, November 6, 2013 10:58 PM, BOB <RemoveMEbobscncRemoveMEspamRemoveMEcharter.net> wrote:
After much reading I think a robot with a drill attachment.
as you apply down pressure the robot front lifts. Start the drill. When the robot drops the drill is through the ice.  Take a measurement and move on.

With a small GPS unit and a radio link you could map out a body of water or ice.

Something to think about for when I have too much time on my hands.

Bob

On 11/6/2013 7:29 PM, Robert Rolf wrote:
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-- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
mailman.mit.edu/mailman/listinfo/piclist
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