Searching \ for 'Electrolytic Capacitors and Heat [OT]' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=
Search entire site for: 'Electrolytic Capacitors and Heat [OT]'.

Truncated match.
PICList Thread
'Electrolytic Capacitors and Heat [OT]'
1998\09\15@131951 by lilel

flavicon
face
Ok, so this time it doesn't have a PIC in it.  But my prototype IS on
the same table as my ICEPIC, so it's remotely related.....


I'm having trouble with an electrolytic capacitor (100uF, 85 C,
50WVDC) that drops in  value as it gets hot.  It is in an RC
timing circuit, so a change in capacitance is a problem.  The circuit
has to work in an environment that starts at room temperature, and
climbs to 80C.  I don't know how mush the capacitor drops, but the
slope of the voltage on the capacitor gets steeper the hotter it
gets.

The question is:  Do all electrolytic capacitors change capacitance
as they get hot?  If so, how much and what direction?  Is there a
type that is more stable at higher temperatures?
-- Lawrence Lile

    "The ideal design has zero parts"  -
           (attributed to Harold Hallikainen)

Download AutoCad blocks for electrical drafting at:
http://home1.gte.net/llile/index.htm

1998\09\15@133414 by Sean Breheny

face picon face
Hi Lawrence,

All electrolytic caps are terrible when it comes to tempco, initial
manufacturing tolerance, and leakage. Perhaps you could use a larger R, and
a smaller C from a different capacitor type, such as polystyrene,
polycarbonate, or polypropylene. There may be some other types that are
good for tempco as well, I just took these from a table in Horowitz and
Hill. How long a delay are you looking for in your RC circuit? How much
tolerance is allowed. Also, I think that electrolytic caps won't tolerate
many repeated changes in temp from room temp to 80C.

Good luck,

Sean


At 11:57 AM 9/15/98 +0000, you wrote:
{Quote hidden}

+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
spam_OUTshb7TakeThisOuTspamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\09\15@150406 by Peter L. Peres

picon face
> RC timing, capacitor C changes with rising temp

The only option is to use a thermistor (ptc) together with the original
timing resistor (in series).

I don't know how accurate your timing must be but using an 85 C cap at 80
C is not such a good idea imho. A 105 C rated one is a better choice imho.
This will also likely be more accurate and have less problems with
temperature changes (different electrolyte etc).

BTW does the mains voltage not affect your design ? It can vary by +5/-5%
usually, f.ex. due to increased load in a longer house feed line.

hope this helps,

Peter

1998\09\15@152443 by daddio

flavicon
face
Thank you for your quick response and you help.  It is greatly appreciated.


Max

-----Original Message-----
From: Peter L. Peres <.....plpKILLspamspam@spam@ACTCOM.CO.IL>
To: PICLISTspamKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Date: Tuesday, September 15, 1998 3:03 PM
Subject: Re: Electrolytic Capacitors and Heat [OT]


{Quote hidden}

1998\09\15@175707 by paulb

flavicon
face
Lawrence Lile wrote:

> Ok, so this time it doesn't have a PIC in it.  But my prototype IS on
> the same table as my ICEPIC, so it's remotely related.....

> I'm having trouble with an electrolytic capacitor ... It is in an RC
> timing circuit, so a change in capacitance is a problem.

 Timing circuit ... long time constant ... stability  ...

 Isn't it just *so* obviously time you put a PIC in it and made it work
simply and reliably first off?
--
 Cheers,
       Paul B.

1998\09\15@210912 by Russell McMahon

picon face
An important additional aspect - you didn't ask this but it's vital.
Electrolytic Capacitor lifetime drops by approx a factor of 2 times
(pessimistic rule of thumb) for every 10 degree Celsius temperature
rise. If you are consistently running at 80C you MUST use 105 degree
C capacitors or your lifetime will be minimal. Specs vary but
typically caps are specified for eg 1000 hours at rated temperature
on the assumption that you will run them MUCH lower than this. eg an
85C part run at 45C is 40 degrees lower so lives 2^4 = 16 times
longer = 16000 hours. Actually it would be somewhat better than this.
Pseudo Randomly opening my Philips cap book (well thumbed page) gives
specs for their 037 series which are common.
85C    2000 hours
40C    70000 hours
.
Another CRITICAL fact is that if the capacitor has no voltage applied
or low voltage compared to its rating it will die much quicker at
elevated temperature. The above 037 caps are rated for 500 hours at
85C when not powered !!!!. this may not be intuitive!




{Original Message removed}

1998\09\16@021137 by William Chops Westfield

face picon face
Anyone have a quick cheat-sheet for different types of electrolytic
capacitor types?  The didgikey catalog lists lots, and skimming the
"benefits" of each type seems to show the same benefits for each type.
(I don't necessarilly need an explanation of all the panasonic types,
just a general feeling of the types available.  My BSEE education didn't
include any such practical matters.)

I'd guess low leakage, low esr, low inductance, high temp, and high tolerance
as "special classes" that ought to be popular?  And where do tantalums fit
in the picture, anyway.

Thanks
Bill W

1998\09\16@103435 by Martin McCormick

flavicon
face
William Chops Westfield writes:
>I'd guess low leakage, low esr, low inductance, high temp, and high tolerance
>as "special classes" that ought to be popular?  And where do tantalums fit
>in the picture, anyway.

       Electrolytic capacitors are definitely not precision devices.
I have been told that there is as much as a 50% tolerance in the
actual capacitive value from one sample to the next and, as several
others have stated, heat positively kills them.  More heat kills them
more quickly, but it's just a matter of time before they dry out and
stop being capacitors.  All the ones I have seen fail that didn't
short and become firecrackers did so by gradually loosing their
capacitance until they effectively took themselves out of the circuit.
In this case, a little heat from a heat gun, hair drier, or warm
soldering tip will bring them back a little until they cool back
down.  This helps find the bad ones much like Freeze Mist, only in
reverse.  You can also take a known good capacitor of suitable value
and rating and momentarily sub it across the suspect capacitor to see
if the trouble goes away.

       As for tantalums, they tend to be high in capacitance for
their size.  If they go bad or are connected in reverse, they tend to
announce this condition with a horrendous bang, lots of shrapnel, and
a bad odor.  All that's usually left afterwards are the two leads with
gobs of burnt material attached to the ends.  I had one go off in my
hand when I accidentally connected it to a reverse polarity terminal
on a board I was trying to trouble-shoot.  It burned a nice little
spot on my thumb and really got my attention.

       As for time constants, Most of the projects I have read about
or built that worked well  used silver mica or polistyreen capacitors.
I have built plenty of circuits with electrolytics as the C in a RC
constant, and they really don't work all that well over a long period
of time.

       After a while, they may start to reduce their capacitance as
they dry out or they  may develop leakage current which acts like a
resistor in parallel or they may just go "bang!"  I have joked before
that electrolytic capacitors should be socketed like tubes used to be
for all the grief they cause.

       Obviously, electrolytics serve a valuable function in
electronics, but they are the weak link.

Martin McCormick

1998\09\16@130410 by Morgan Olsson

picon face
I just want to mention dry electrolytics;

Good:
They can«t dry out (are already...)
Sustain very high temperature (and also low) with long life
Don't have the sudden self-short potential of tantalums

Bad:
Expensive

Don't know:
cap/temp coefficient

BTW: Thanks everybody responding to my accelerometer request
My customer want the solution ready yesterady (as always)   :)


/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  EraseMEmrtspam_OUTspamTakeThisOuTiname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\09\16@130418 by Morgan Olsson

picon face
(resending as it did not make piclist)

At 11:57 1998-09-15 +0000, you wrote:
>Ok, so this time it doesn't have a PIC in it.  But my prototype IS on
>the same table as my ICEPIC, so it's remotely related.....
>
>
>I'm having trouble with an electrolytic capacitor (100uF, 85 C,
>50WVDC) that drops in  value as it gets hot.  It is in an RC
>timing circuit, so a change in capacitance is a problem.  The circuit
>has to work in an environment that starts at room temperature, and
>climbs to 80C.  I don't know how mush the capacitor drops, but the
>slope of the voltage on the capacitor gets steeper the hotter it
>gets.
>
>The question is:  Do all electrolytic capacitors change capacitance
>as they get hot?  If so, how much and what direction?  Is there a
>type that is more stable at higher temperatures?
>-- Lawrence Lile

If I remember correct tantalum capacitors *increase* capacitance at raised
temperature.  Maybe use a 47uF tant and 47uF elyt (or another combination)
in parallel to cancel the drift?

Other idea is to use a positive temperature dependant resistor PTC in
either the timing ckt or trigger level ckt.  Or, preferrably use NTC in
trigger ckt since you then can use NTC.

Might be hard to get the same for all temperatures anyway.

Any method to use much lower capacitance, and there will be much more
alternatives. Maybe use a CMOS4060 (osc + 14bit cntr?)

Why not a cheap pic and ceramic resonator?
/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrtspamspam_OUTiname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\09\16@163625 by lilel

flavicon
face
To summarize several comments:

Electrolytic capacitors reek.

Unfortunately I'm trying to build an extremely low cost device, and
I can tolerate a lot of variation from part to part.  I looked into a
PIC design, and it effectively increases the price of the whole
assembly by some 30% (do the math, this thing is really cheap.)

So ya get what ya pay for.

I Spent the last 2 days building an oven that can test components at
elevated temperatures and graph them vs. temperature.  My
conclusions are that electrolytics have a slightly positive
temperature coefficient (this was verified by a mfr)  a 100 uF
nominal cap at 25C was more like 105 uF at 85C.  That was just before
the can split open, however (sheesh) at 120C.

I've been afraid to use tantalums because the probably have excessive
leakage compared to a low leakage electrolytic.  But I'm not so sure.
I may look into tantalums again soon.

My first experiment which seemed to indicate capacitance dropping is
still a mystery.  There are several components that could be
exibiting troublesome leakage or tolerance change at elevated
temperatures.  I'm testing them in my oven one by one.  I think my
original conclusion was erroneous.

To sum up, at high temperatures diodes are not diodes, resistors
become thermistors, capacitors become bombs, SCR's become
transistors, black becomes white,  politicians become honest, and
pigs can fly   etc. etc.   This is worse than designing for RF
circuits, it's like black magic.

Everyone who suggested a Timer or a PIC is right.

-- Lawrence Lile


Download AutoCad blocks for electrical drafting at:
http://home1.gte.net/llile/index.htm

1998\09\16@164245 by lilel

flavicon
face
>
> BTW does the mains voltage not affect your design ? It can vary by
> +5/-5% usually, f.ex. due to increased load in a longer house feed
> line.


Mains voltage will definitely affect me.  My appliance uses resistive
heating, so the power (and temperature) will vary as the square of
the mains voltage.  My circuit uses linear components (resistors,
etc.) and the time varies linearly with mains voltage.  Extreme
variations in line voltage (105 down from 120) will cause really poor
behavior, but small variations (5%) will cause similar size
variations in performance.  The short answer is the timer will
compensate for line voltage a little bit, and this little bit is
within acceptable limits.
-- Lawrence Lile

"If this were easy they'd have hired somebody else to do it."

Download AutoCad blocks for electrical drafting at:
http://home1.gte.net/llile/index.htm

1998\09\16@181653 by Russell McMahon

picon face
Last question first - its important:

> And where do tantalums fit
>in the picture, anyway.

Tantalums have their place but should be avoided if at all possible.
Tantalums have excellent ESR and low impedance and small physical
size per capacity relative to wet aluminium.
HOWEVER,
and it is a big however, their voltage rating is critical - if an
overvoltage spike even slightly above their rated value is applied
they often (usually?) break down and go short circuit. if the circuit
has enough energy they produce some or all of noise, flame,
explosion, smell and dispersion of metallic tantalum. I have seen all
of these at one sitting on occasion - something like a good Guy
fawkes day cracker.
Solid aluminium is about as good, doesn't have this problem and may
be cheaper.
Fun demonstration.
   Turn off bench supply
   Place tantalum cap across terminals with reverse polarity.
    Stand back.
   Turn on supply.
   Enjoy.
   Repeat with aluminium cap.

>I'd guess low leakage, low esr, low inductance, high temp, and high
tolerance
>as "special classes" that ought to be popular?

You seem to have thought of most of the categories.
Presumably high tolerance means high precision?
There is also 'low profile" usually meaning high capacitive density
per size
.
The Philips electrolytic capacitor handbook "PA01" or similar has a
range of information and may be free depending on your supplier.
.
Philips identify -
.
Low leakage    RLC013
Bipolar             RB036, RBA036
High voltage    RSH
Low Z               RLI135
105 C               RSX164
125 C               RHT165
105c, very low Z    RVI 136
Types RSL, RLI, RLL, RML are also long life - 1500-4000 hours at
105C.
RHT RSX RVI are extra long life - 1500 hrs at 125 C. >4000 hrs at
105C
.
Power cans come in economy. euro-din, long life (5000-10000 hrs at
105C!)



.
Other makers have similar types.
Philips are always there (or have been for the last xxx years).


>
>Thanks
>Bill W
>

1998\09\16@191731 by Sean Breheny

face picon face
Hi All,

Quick question:

In a class that I was taught here the prof. said that electrolytic caps
consisted of rolled up conductors internally (to increase surface area)
with the electrolytic dielectric deposited between the layers of the roll.

Now, I know that non-electrolytic caps often use this configuration (old
paper caps, some mica caps, etc.), but DO electrolytics? I seem to remember
sawing one open years ago and finding no roll of anything, mostly a large
piece of insulating material (rubber?) and I can't remember the rest of the
details (it was when I was only about 7 years old!). I may saw one open now
to see this, but I am a bit relutcant because I'm not sure of whether the
dielectric might be hazardous, however I have had them blow up before and
it didn't hurt me (although it didn't get in my eyes!). I did have a rude
awakening a while back when I found out that some RF power semiconductors
use BeO (Beryllium Oxide) internally (I think as a compond to ensure proper
heat transfer). Well anyway, I found out that this is a VERY hazardous
compound if its dust is inhaled (causes liver damage even in rather small
quantities) and its is possible for its dust to be created if you say,
crack an RF power transistor or break/bend one of its leads.


Thanks for any answers,

Sean

At 12:21 AM 9/17/98 +1200, you wrote:
{Quote hidden}

+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
@spam@shb7KILLspamspamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\09\16@225311 by Mike Keitz

picon face
On Wed, 16 Sep 1998 19:15:43 -0400 Sean Breheny <KILLspamshb7KILLspamspamCORNELL.EDU>
writes:
>I seem to remember sawing one open years ago and finding no roll of
>anything, mostly a large piece of insulating material (rubber?) and I
>can't remember the rest of the details

If you take another one apart, you'll find there is indeed a roll of two
aluminum plates seperated by paper inside.  However it doesn't work like
a paper capacitor (the paper isn't the dielectric).  Instead the paper is
dampened with an electrolytic solution that makes it conduct quite well.
The paper serves only to seperate the aluminum plates from touching and
shorting the capacitor out.

Actual capacitor action occurs on the surface of the plates.  Notice that
they aren't shiny aluminum, instead they are dull gray.  That's because
they have been treated by etching (for more surface area) and a thicker
layer than natural of aluminum oxide built up.  The oxide serves as the
capacitor's dielectric.  The underlying metal is one of the plates, and
the liquid electrolyte from the damp paper is the other.

So, the unit contains effectively two capacitors in series, one at each
plate.  Usually the negative plate has less oxide on it, as the positive
one has to withstand the operating voltage of the capacitor.  The thin
oxide on the negative plate causes it to have a large capacitance, and
the positive plate largely determines the effective capacitance.
Capacitors designed for non-polarized operation have both plates the
same, thus they have to be larger for the same capacity.  But even an
ordinary one can withstand some reverse voltage since the negative plate
has a thin oxide on it.

> I'm not sure of whether the dielectric might be hazardous.

I've never heard of it being hazardous.  It is just an inorganic salt of
some sort.  There may be some proprietary additives.

>some RF power semiconductors use BeO (Beryllium Oxide) internally (I
>think as a compond to ensure proper heat transfer). Well anyway, I found

>out that this is a VERY hazardous compound if its dust is inhaled
(causes
>liver damage even in rather small quantities)

BeO is one of the less toxic forms of berylium since it is quite
insoluble and unreactive.  However it will cause lung and skin damage if
contacted in powder form.  Early (before 1949) fluorescent lamps
contained BeO powder as one of the phosphors.  It was determined to be
toxic after lamp factory workers started becoming ill.  Although BeO was
taken out of the formula, advice to not handle the powder from broken
lamps persists to this day (though it is still a good idea not to because
of the mercury).

> and its is possible for its dust to be created if you say,
>crack an RF power transistor or break/bend one of its leads.

The BeO is in the round insulating base disk between the transistor die
and the mounting flange or stud.  In transistors with the emitter
connected to a metal case, there is a small piece of BeO inside. It is
used there because of very high thermal conductivity, about half that of
copper, which is impressive for a material that is a good electrical
insulator.  The top cap of a ceramic RF power transistor is made of
ordinary alumina ceramic.  You may also encounter BeO in hybrid modules
especially from military equipment, and in insulating plates under power
transistors (where mica or gray plastic is used now).

Since BeO is widely used in industry, a lot has been written about its
safe handling.  Any college library should have material to research
further.


_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]

1998\09\16@230402 by Mike Keitz

picon face
On Wed, 16 Sep 1998 15:35:16 +0000 Lawrence Lile <RemoveMElilelTakeThisOuTspamtoastmaster.com>
writes:

>Unfortunately I'm trying to build an extremely low cost device, and
>I can tolerate a lot of variation from part to part.  I looked into a
>PIC design, and it effectively increases the price of the whole
>assembly by some 30% (do the math, this thing is really cheap.)

Morgan Olson suggested the 4060 chip, which sounds like a good idea to
me.  It is a 14-stage counter with a few extra inverters to make an RC
oscillator out of.  If you use the last stage as the output, it'll go
high after 8192 RC periods.  You'd need an RC network on the reset pin to
be sure the count starts at 0 after the power is turned on.  Speaking of
power, it can run from 3 to 18 V, a big advantage over PIC.  Probably no
regulator will be needed.

>I've been afraid to use tantalums because the probably have excessive
>leakage compared to a low leakage electrolytic.  But I'm not so sure.
> I may look into tantalums again soon.

I think the tantalum will work well, but ruin the budget.  They are
usually used as a last resort in consumer devices when leakage would be a
problem, such as the loop filter in a PLL.


_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]

1998\09\16@232815 by Sean Breheny

face picon face
Thanks, Mike, for the answer.

Exceptionally clear! Wish my prof. had said that.

More knowledge gleaned from the great PICLIST.

Sean

At 10:51 PM 9/16/98 -0400, you wrote:
{Quote hidden}

+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
TakeThisOuTshb7EraseMEspamspam_OUTcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\09\17@011311 by Dwayne Reid

flavicon
face
>Mains voltage will definitely affect me.  My appliance uses resistive
>heating, so the power (and temperature) will vary as the square of
>the mains voltage.  My circuit uses linear components (resistors,
>etc.) and the time varies linearly with mains voltage.  Extreme
>variations in line voltage (105 down from 120) will cause really poor
>behavior, but small variations (5%) will cause similar size
>variations in performance.  The short answer is the timer will
>compensate for line voltage a little bit, and this little bit is
>within acceptable limits.

You might be able to fake out the E^2 power changes in the heaters by
putting a zener diode in series with the timing resistor (assuming the whole
thing is line powered).  Pick the zener voltage so that the timer is about
the right time at both 105V and 120V.  Essentially, you shift the linear
change in time as V varies so that you can increase the slope of that change
to more closely match the power curve.  I'm assuming that zeners don't cost
much more than resistors in the kinds of quantities you buy in.  Just a thought.

dwayne


Dwayne Reid   <RemoveMEdwaynerspamTakeThisOuTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice     (403) 487-6397 fax

1998\09\17@023300 by Morgan Olsson

picon face
I often mend/upgrade a varitey of equipment.

In my experience there is larger probability of a electrolytic being dried
out than a tantalum being damaged.

Also a shorted tant is much easier to identify than a wrong value elytic.

This is one of the criteria making I most often prefer using tants,
selecting to double my operating voltage, except for stages where
overvoltage might be a concern where i use elytics.

Other concerns is greater life time, small size, and low leakage.

/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrtEraseMEspam.....iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\09\17@035523 by g.daniel.invent.design

flavicon
face
Mike Keitz wrote:

<cut>
> The BeO is in the round insulating base disk between the transistor die
> and the mounting flange or stud.  In transistors with the emitter
> connected to a metal case, there is a small piece of BeO inside. It is
> used there because of very high thermal conductivity, about half that of
> copper, which is impressive for a material that is a good electrical
> insulator.  <cut>

Diamond is the realy awesome thermal conductor, insulator etc.
(very good for heat exchangers if you can afford it).

regards,
Graham Daniel.

1998\09\17@111825 by lilel

flavicon
face
> Morgan Olson suggested the 4060 chip, which sounds like a good idea
> to me.

I've worked with a design using the 4060, as well as the 4541
counters.  The last board I worked on using a 4541 costs $1.80 in
quantity, this one costs well under US$1.00.  I'd like to have the
luxury of using a 4541 or 4060.

Despite the warnings  (which are well taken and much appreciated) I'm
going to continue looking at an RC timer.
-- Lawrence Lile

"If this were easy they'd have hired somebody else to do it."

Download AutoCad blocks for electrical drafting at:
http://home1.gte.net/llile/index.htm

1998\09\17@112547 by lilel

flavicon
face
> I seem
> to remember sawing one open years ago and finding no roll of
> anything, mostly a large piece of insulating material (rubber?) and
> I can't remember the rest of the details (it was when I was only
> about 7 years old!). I may saw one open now to see this, but I am a
> bit relutcant because I'm not sure of whether the dielectric might
> be hazardous, however I have had them blow up before and it didn't
> hurt me (although it didn't get in my eyes!).

I've started wearing safety glasses anytime I'm working on live
circuits or soldering (When I'm soldering anything big enough to see
through blurry safety glasses!)  or when sawing open components out
of curiosity!

The first time an electrolytic exploded on my bench it shot a hole in
the cieling, and blasted paper all over my CB. Could've put out an
eye.   My 12V power supply had failed and began putting out 60VDC,
which fried the main filter cap.  That was when a handheld four
function calculator cost $150.

Meanwhile I sawed open a golfball, without safety glasses (Why do
young engineers saw so many things open?) and it was some kind of
special pressurized core, that blasted me in the face with gunk.  I
sawed open a shotgun shell without killing myself, and a few caps
too.  Don't saw things open without safety equipment and maybe a good
shower handy.

Just yesterday I shorted two 120V leads together, destoying a good
part of the leads and a signifigant chunk of a PC board, meanwhile my
Tech put an electrolytic in backwards and shut it off when it began
to sound like frying chicken.  A bad day, all around.  I'd like to
still be watching sunsets when I retire.  These things explode and
arc and spark, and a little polycarbonate lens between you and it may
be crucial someday.
-- Lawrence Lile

"If this were easy they'd have hired somebody else to do it."

Download AutoCad blocks for electrical drafting at:
http://home1.gte.net/llile/index.htm

1998\09\17@112839 by John Shreffler

flavicon
face
part 0 611 bytes
Metallic Be is very toxic.  My first job out of school was at
a division of GM that made gyroscopes for missile guidance.
Be has a useful characteristic:  virtually zero temp coefficient,
so that the tight tolerances of the air bearings are maintained.
The dust from the tooling will do you in big time.  Every
lathe and milling machine was inside a plexiglass air chamber
with air pumped to huge filters on the roof.

I have never seen any cautionary notes on Be oxide, however.
Some compounds of hazardous elements are safe.  Sodium
and Chlorine are both nasty stuff.  But we sprinkle NaCl on our
hamburgers.

1998\09\17@121245 by John Payson

flavicon
face
|Anyone have a quick cheat-sheet for different types of electrolytic
|capacitor types?  The didgikey catalog lists lots, and skimming the
|"benefits" of each type seems to show the same benefits for each type.
|(I don't necessarilly need an explanation of all the panasonic types,
|just a general feeling of the types available.  My BSEE education didn't
|include any such practical matters.)

|I'd guess low leakage, low esr, low inductance, high temp, and high tolerance
|as "special classes" that ought to be popular?  And where do tantalums fit
|in the picture, anyway.

Capacitor manufacturing technology does change from time to time, so knowing tha
t froboznium
silicate caps are good from an ESR standpoing isn't as important as knowing what
properties
of electrolytic caps are normally less than ideal and recognizing which properti
es really
matter in which applications.

One way to look at a normal electrolytic cap (or any cap for that matter) is as
follows:
         R1
  +---+-/\/\--- TERMINAL 1
  |   |
C1 =   > R2
  |   <
  |   |   L1
  +---+--UUUU-- TERMINAL 2

C1 is an ideal cap (100% efficient energy storage, etc.).  You'd like C1's capac
itance to
match precisely the value specified, for R1 and L1 to be zero, and R2 to be infi
nite.
Unfortunately, real caps don't behave ideally in ANY of those regards.  Since im
provements
in any of those characteristics will cost money (significant money in the case o
f large
caps) it is usually desirable to determine which of those characteristics partic
ularly
matter in any given application and pay to improve only those that do.

If, for example, you need a cap to keep a sleeping PIC powered for a day or so,
it doesn't
really matter what R1 and L1 are; since the PIC draws basically no current, ther
e won't be
any real losses in those.  If R2 isn't huge, however, the cap will lose charge e
ven though
the PIC is hardly drawing anything.  In such an application, therefore, what's n
eeded is a
cap with a large capacitance (the exact value doesn't matter) and minimal leakag
e (maximum
R2); R1 and L1 can be huge, though, and it won't matter.  If you look in Digi-Ke
y, you'll
see "SuperCaps" that meet the above characteristics: R1 and L1 are comparatively
big, but
for this application that doesn't matter.

On the other hand, if you're using a cap to try to filter half-wave AC for a hig
h-current
load, R2 doesn't really matter (since the cap only needs to keep a charge for a
few ms
between waves) but R1 must be small.  If R1 is even 1/10 ohm and the load draws
10 amps,
then R1 will drop a volt much of the cycle; not only does this mean your load vo
ltage has
more ripple than would be ideal, but it also means almost 10 watts of heat will
be diss-
ipated WITHIN the capacitor.  If the cap isn't designed to handle that, such tre
atment
could easily cause it to fail catastrophically.

BTW, my physics professor was explaining to me about electrolytics and their rat
ed voltage:
if you place across a cap voltage in excess of its rating, the cap will leak off
the excess
voltage (generating heat) but will also build up the electrolyte inside which wi
ll have the
simultaneous effects of increasing the cap's breakdown voltage and reducing its
capacitance.
If you want to try this, you need to limit the power going into the cap (so it d
oesn't blow
its top) but my physics professor said that many caps are actually manufactured
this way:
starting with a large-value, low-voltage cap, slowly drive it with enough voltag
e to produce
more electrolyte until the cap's voltage/capacitance are within the desired spec
ification.
Cute, huh?

1998\09\17@130448 by Eisermann, Phillip

flavicon
face
> > I seem
> > to remember sawing one open years ago and finding no roll of
> > anything, mostly a large piece of insulating material (rubber?) and
> > I can't remember the rest of the details (it was when I was only
> > about 7 years old!). I may saw one open now to see this, but I am a
> > bit relutcant because I'm not sure of whether the dielectric might
> > be hazardous, however I have had them blow up before and it didn't
> > hurt me (although it didn't get in my eyes!).
>
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!
>
>
       This is, IMHO, probably one of the most important pieces of
advice
       ever given.

       [snip examples of how to put out an eye]


       you only have one set of eyes. they cannot be replaced. I used
to
       feel silly wearing my safety glasses while doing electronics
work,
       so i just didn't. i thought, what can happen, after all?

       until i had a similar experience, and a cap blew up in my face,
and
       nailed me in the forehead, just above my left eye. I now have a
       little 'indentation' there...

       -phil

1998\09\17@135849 by Peter L. Peres

picon face
On Wed, 16 Sep 1998, Lawrence Lile wrote:

> > BTW does the mains voltage not affect your design ? It can vary by
> > +5/-5% usually, f.ex. due to increased load in a longer house feed
> > line.
>
> Mains voltage will definitely affect me.  My appliance uses resistive
> heating, so the power (and temperature) will vary as the square of
> the mains voltage.  My circuit uses linear components (resistors,
> etc.) and the time varies linearly with mains voltage.  Extreme
> variations in line voltage (105 down from 120) will cause really poor
> behavior, but small variations (5%) will cause similar size
> variations in performance.  The short answer is the timer will
> compensate for line voltage a little bit, and this little bit is
> within acceptable limits.

The more I hear about this the more often I keep saying "how much is a
4060 in 10.000's" ? You can use a 4060 or 4040 clocked by the mains. With
2 or 3 1N4148 diodes to select the required end voltage you get a very
accurate timer. These parts require so low a power that they can be run
relatively safely from rectified mains through a resistor with a 2 mA LED
and another resistor setting the voltage. Clock can be fed directly from
mains through another resistor (5.6 Megs I've used on 220/310 V). There is
a cunning thyristor firing circuit that uses the charge storage principle.
It uses the miserly power supply of the CMOS and a primitive gate to
slowly charge a large capacitor without loading the supply and then when
the time comes, this energy is available to fire the triac or thyristor.
All of this can be done by a PIC of course (again).

Now, for capacity affecting temperature and getting rid of this: Once upon
a time there used to be a lot of bucket charger timers and other circuits.
Apparently their secret has been lost. I'll refresh this as I think that
it might solve your problem (in an almost analog way <g>).

A bucket charger is a circuit where there are 2 capacitors. One is large
and serves to integrate the charge, and the second is small and is charged
to a constant voltage and discharged into the large capacitor on every
cycle of a constant frequency clock (such as, the mains). The temperature
dependency of such a circuit can be zeroed as, if the 2 capacitors have
the same temperature coefficient, then the temperature won't affect the
final voltage vs. time on the integrating cap (I leave the proof as an
exercise). The simpler incarnations of this system require only 2 diodes,
but a more accurate one adds a zener, like this:

       R1          C1       D1
AC O---/\/\/\---*---||---*---|>|---*---O Vout, rises in steps from 0
               |        |         |
              ---      ---        |
                /      / \       ---
              / \      ---       ---
              ---       |         |
               |        |         |
              ===      ===       ===
            Zener1     D2        C2

The key is the fact that C1 << C2. The zener is required to make the
system more accurate but if the mains (AC) voltage deviation is acceptable
then it can be missing. R1 limits the inrush through D1 and C1 and C2 and
must be dimensioned with consideration of the zener current, dissipated
power and its effect on charging/discharging C1 fully (this is the 2nd
key requirement) on each half cycle.

NOW can we move to more PICish things ? This theread has been going on for
so long, that the next time i'll post a timer implementation source for
16C54 ;)

Peter

1998\09\17@143541 by Peter L. Peres

picon face
> safety glasses in electronics lab

FYI every school now has the pupils wear them, the military included as
far as i know, EVERYWHERE. I don;t know if it's insurance-driven or
whether they have finally realized that a 100 uF / 350 V charged cap is
far more dangerous than a hammer.

Peter

1998\09\17@145904 by goflo

flavicon
face
Peter L. Peres wrote:
> > safety glasses in electronics lab
> FYI every school now has the pupils wear them, the military included as
> far as i know, EVERYWHERE. I don;t know if it's insurance-driven or
> whether they have finally realized that a 100 uF / 350 V charged cap is
> far more dangerous than a hammer.

I got bagged WITH safety glasses on by a tiny metal splinter from
a hammer-stroke near me. Oblique fire, so to speak. Worked out OK,
but better avoided.

Regards, Jack

1998\09\17@150313 by Ansel Sermersheim

flavicon
face
Lawrence Lile <EraseMElilelspamtoastmaster.com> writes:
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!
[snip]
> Just yesterday I shorted two 120V leads together, destoying a good
> part of the leads and a signifigant chunk of a PC board, meanwhile my
> Tech put an electrolytic in backwards and shut it off when it began
> to sound like frying chicken.  A bad day, all around.  I'd like to
> still be watching sunsets when I retire.  These things explode and
> arc and spark, and a little polycarbonate lens between you and it may
> be crucial someday.
> -- Lawrence Lile

Just had an interesting idea that might be useful.  If you wear
glasses normally, make sure to get them with polycarbonate lenses.  I
always do, and it's saved my eyesight a couple of times.

If you don't wear glasses, why not get some?  I'm sure the lens shops
would have no problem making flat glasses; it wouldn't be hard.
They'd be a lot more comfortable than safety glasses, though not quite
as sturdy.  (However, polycarb normal glasses are pretty strong.  Got
hit once by a paperclip shot off a rubber band (don't ask) and it
didn't even make a scratch.)

-Ansel
ObPIC: does anyone have plans to a PIC programmer?  I've got quite a
well-established junk box, but no $$$ to make one.

It would be really nice if I can work with it in Linux.
--
GCS/CM/IT d- s+:-- a--- C++++ UL++++>$ V? P+++ L++(++++) E++ W+ N++ w---
M-- PS++ PE Y+ PGP++ t++(*) 5+++ X+ R tv b++++ DI++++ D---(+) G++ e*>++
h!>++ r--- y?

1998\09\17@150313 by Ansel Sermersheim

flavicon
face
Lawrence Lile <RemoveMElilelEraseMEspamEraseMEtoastmaster.com> writes:
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!
[snip]
> Just yesterday I shorted two 120V leads together, destoying a good
> part of the leads and a signifigant chunk of a PC board, meanwhile my
> Tech put an electrolytic in backwards and shut it off when it began
> to sound like frying chicken.  A bad day, all around.  I'd like to
> still be watching sunsets when I retire.  These things explode and
> arc and spark, and a little polycarbonate lens between you and it may
> be crucial someday.
> -- Lawrence Lile

Just had an interesting idea that might be useful.  If you wear
glasses normally, make sure to get them with polycarbonate lenses.  I
always do, and it's saved my eyesight a couple of times.

If you don't wear glasses, why not get some?  I'm sure the lens shops
would have no problem making flat glasses; it wouldn't be hard.
They'd be a lot more comfortable than safety glasses, though not quite
as sturdy.  (However, polycarb normal glasses are pretty strong.  Got
hit once by a paperclip shot off a rubber band (don't ask) and it
didn't even make a scratch.)

-Ansel
ObPIC: does anyone have plans to a PIC programmer?  I've got quite a
well-established junk box, but no $$$ to make one.

It would be really nice if I can work with it in Linux.
--
GCS/CM/IT d- s+:-- a--- C++++ UL++++>$ V? P+++ L++(++++) E++ W+ N++ w---
M-- PS++ PE Y+ PGP++ t++(*) 5+++ X+ R tv b++++ DI++++ D---(+) G++ e*>++
h!>++ r--- y?

1998\09\17@152354 by Sean Breheny

face picon face
[ALL INTERESTING STUFF ABOUT SAFETY SNIPED]

Thanks for the advice, guys. When I get a chance, I will put on a pair of
safety glasses and saw open another electrolytic to satisfy my curiosity
once again.


Oh, I actually have one additional question relating to what Mike Keitz
said about electrolytic caps. He said(paraphrased) that thay are really two
caps in series, and that the dielectric is thicker on the positive plate
and that this is why they can withstand much greater voltage in the proper
polarity than in reverse. What I don't understand is this: Whichever way
you hook them up, the greater voltage will be across the positive end cap
because it has the smaller cap value. SO it would seem to me that there
must be something else causing them to be polarized.

Thanks again,

Sean


+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
RemoveMEshb7spam_OUTspamKILLspamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\09\17@153044 by goflo

flavicon
face
Ansel Sermersheim wrote:

> Just had an interesting idea that might be useful.  If you wear
> glasses normally, make sure to get them with polycarbonate lenses.  I
> always do, and it's saved my eyesight a couple of times.
>
> If you don't wear glasses, why not get some?  I'm sure the lens shops
> would have no problem making flat glasses; it wouldn't be hard.

Did just that quite a few years ago, for the reasons you cite - Wore
them for years - Dropped them one day & they shattered. Not polycarb.
Made by a reputable lab, and quite expensive.
Just thought I'd mention it.

Jack

1998\09\17@154504 by William Chops Westfield

face picon face
The electrolytics I've taken apart (recently, generally trying to remove
them from PC boards) have all had a single Al "foil-like" conductor, and
a fiber separator/electrolyte holder.  I've assumed that the foil serves
as one electrode, and the electrolyte is conductive enough to serve as
the other electrode (which explains polarity pretty nicely.)  I haven't been
careful enough to see what mechanism is used to make electrical contact
with the fiber/electrolyte...

BillW

1998\09\17@160408 by Martin McCormick

flavicon
face
       I was just thinking that another possible approach is to have
some kind of heat shield around the electronics so they never reach
high temperatures.  something along the lines of putting the board on
some part of the case that is not going to get hot immediately if at
all.

       The newer Kodak Carrousel slide projectors I used to fix in my
previous job did amazing things with thin baffles of metal when it came to
keeping the searing heat of the lamp out of places where it didn't
belong.

       Surely, there is a place in the device in question where
things don't get hot.  I can imagine a little well containing the
circuit, anything to keep it away from the heat.

Martin McCormick

1998\09\17@174639 by Morgan Olsson

picon face
At 10:37 1998-09-17 -0500, you wrote:

[snip good explanation of electrolytic cap internal electrics]

>BTW, my physics professor was explaining to me about electrolytics and
their rated voltage:
>if you place across a cap voltage in excess of its rating, the cap will
leak off the excess
>voltage (generating heat) but will also build up the electrolyte

You must mean the *dielectric* (the alumina oxide layer)

> inside which will have the
>simultaneous effects of increasing the cap's breakdown voltage and
reducing its capacitance.
>If you want to try this, you need to limit the power going into the cap
(so it doesn't blow
>its top) but my physics professor said that many caps are actually
manufactured this way:
>starting with a large-value, low-voltage cap, slowly drive it with enough
voltage to produce
>more electrolyte until the cap's voltage/capacitance are within the
desired specification.
>Cute, huh?

Interesting

/Morgan

/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  RemoveMEmrtTakeThisOuTspamspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\09\17@182100 by paulb

flavicon
face
John Shreffler wrote:

> Some compounds of hazardous elements are safe.  Sodium and Chlorine
> are both nasty stuff.  But we sprinkle NaCl on our hamburgers.

 Fluorine is *far*, *far* nastier but Teflon makes for great frypans!
--
 Cheers,
       Paul B.

1998\09\17@183651 by Mark Willis

flavicon
face
Lawrence Lile wrote:
>
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!

 Another good idea: I decided on some projects (One industrial job
that's on hold for now, for example, runs ~500VDC into a huge
electrolytic bank) to put a wall of 2x4's between the capacitors &
myself;  basically the cap bank is built like a black powder magazine
(stout walls, thinner roof) so the roof will go up if if blows, but stop
most of the hard circuitry & parts.

 In more way than one, I'm glad that one's on hold...  Loud bangs make
me nervous, and startle the girlfriend <G>

 One tech who I think is quite smart has this piece of polycarbonate
(could be SAR plastic or plexiglass?) he can snap onto the edge of his
bench when nervous about a project, this also helps enforce the one-hand
law (he can't reach the project at all without some work, just the
circuit breaker...)  Two problems solved with one chunk of scrap plastic
<G>

 Mark, EraseMEmwillisspamspamspamBeGonenwlink.com

1998\09\17@191116 by Mark Willis

flavicon
face
(BTW the addressing domain munging {maps.nwlink.on.com} stuff in this
message was an accident on my part;  "No Spam" spelled backwards at
least will slot down some usenet address harvesters, I hope.  And if
some bozo tries to send mail to there, no valid DNS entry!  I think my
broswer crashed (again) & I forgot to change it back to normal.)

 My concern - why I send this - is it possible for a non-list member to
post to the list?  (Which I may've appeared to be!)  If so, the whole
list could end up being UCE "Spammed", same as one other list I'm on has
been experiencing...  (3 messages of UCE daily, I'd guess.  Most
sex-related.)

 Mark

Mark Willis wrote:
> <snipped>

1998\09\17@230153 by Dan Larson

flavicon
face
On Thu, 17 Sep 1998 12:43:29 PDT, William Chops Westfield wrote:

>The electrolytics I've taken apart (recently, generally trying to remove
>them from PC boards) have all had a single Al "foil-like" conductor, and
>a fiber separator/electrolyte holder.  I've assumed that the foil serves
>as one electrode, and the electrolyte is conductive enough to serve as
>the other electrode (which explains polarity pretty nicely.)  I haven't been
>careful enough to see what mechanism is used to make electrical contact
>with the fiber/electrolyte...

??? The can, perhaps ???

>
>BillW
>

1998\09\17@234949 by Ansel Sermersheim

flavicon
face
>>>>> "goflo" == goflo  <RemoveMEgofloKILLspamspampacbell.net> writes:

> Ansel Sermersheim wrote:
>> Just had an interesting idea that might be useful.  If you wear
>> glasses normally, make sure to get them with polycarbonate lenses.
>> I always do, and it's saved my eyesight a couple of times.
>>
>> If you don't wear glasses, why not get some?  I'm sure the lens
>> shops would have no problem making flat glasses; it wouldn't be
>> hard.

> Did just that quite a few years ago, for the reasons you cite - Wore
> them for years - Dropped them one day & they shattered. Not
> polycarb.  Made by a reputable lab, and quite expensive.  Just
> thought I'd mention it.

Hmm.  I've never had that problem; if my glasses were glass they'd be
over 3" thick.  I _know_ i'm getting polycarb because they don't
weigh five pounds.

Definately something to be aware of though.


(I apologise for continuing this off-topic thread.  I figure if it
saves a single person's eyesight, it's worth it).
-Ansel
--
I used to be convinced that MicroSquish shipped crap because they simply
didn't give a flying fuck as long as the sheep kept buying their shit.
Now, I'm convinced that they really do ship the best products they are
capable of writing, and *that's* tragic.
  - John C. Randolph, about MS quality control.

1998\09\17@235625 by Mark Willis

flavicon
face
Dan Larson wrote:
>
> On Thu, 17 Sep 1998 12:43:29 PDT, William Chops Westfield wrote:
>
> >The electrolytics I've taken apart (recently, generally trying to remove
> >them from PC boards) have all had a single Al "foil-like" conductor, and
> >a fiber separator/electrolyte holder.  I've assumed that the foil serves
> >as one electrode, and the electrolyte is conductive enough to serve as
> >the other electrode (which explains polarity pretty nicely.)  I haven't been
> >careful enough to see what mechanism is used to make electrical contact
> >with the fiber/electrolyte...
>
> ??? The can, perhaps ???
>
> >
> >BillW

 I think the last diagram I saw had two layers of foil, interleaved
(May be made out of one piece of material with Cathode
foil/insulation/Anode foil/insulation nowadays for reliability etc.?!)
and then wound up, Cathode side out, but it's been a while.  It wouldn't
make sense to have anything beyond the outer layer of
conductor/insulator, remember, as the inverse square law's applicable
here and *any* charge -inside- the roll is completely irrelevant, if I
remember my physics of electronics correctly.)

 I'd trace the wires from the contacts to the PCB (or 1/4" tabs or
whatever) - sort of like "Follow the money" but more like "Follow the
electrons" <G>

 Mark, mwillisSTOPspamspamspam_OUTnwlink.com

1998\09\21@184545 by Ansel Sermersheim

flavicon
face
Lawrence Lile <spamBeGonelilelSTOPspamspamEraseMEtoastmaster.com> writes:
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!
[snip]
> Just yesterday I shorted two 120V leads together, destoying a good
> part of the leads and a signifigant chunk of a PC board, meanwhile my
> Tech put an electrolytic in backwards and shut it off when it began
> to sound like frying chicken.  A bad day, all around.  I'd like to
> still be watching sunsets when I retire.  These things explode and
> arc and spark, and a little polycarbonate lens between you and it may
> be crucial someday.
> -- Lawrence Lile

Just had an interesting idea that might be useful.  If you wear
glasses normally, make sure to get them with polycarbonate lenses.  I
always do, and it's saved my eyesight a couple of times.

If you don't wear glasses, why not get some?  I'm sure the lens shops
would have no problem making flat glasses; it wouldn't be hard.
They'd be a lot more comfortable than safety glasses, though not quite
as sturdy.  (However, polycarb normal glasses are pretty strong.  Got
hit once by a paperclip shot off a rubber band (don't ask) and it
didn't even make a scratch.)

-Ansel
ObPIC: does anyone have plans to a PIC programmer?  I've got quite a
well-established junk box, but no $$$ to make one.

It would be really nice if I can work with it in Linux.
--
GCS/CM/IT d- s+:-- a--- C++++ UL++++>$ V? P+++ L++(++++) E++ W+ N++ w---
M-- PS++ PE Y+ PGP++ t++(*) 5+++ X+ R tv b++++ DI++++ D---(+) G++ e*>++
h!>++ r--- y?

1998\09\21@184545 by Ansel Sermersheim

flavicon
face
Lawrence Lile <KILLspamlilelspamBeGonespamtoastmaster.com> writes:
> I've started wearing safety glasses anytime I'm working on live
> circuits or soldering (When I'm soldering anything big enough to see
> through blurry safety glasses!)  or when sawing open components out
> of curiosity!
[snip]
> Just yesterday I shorted two 120V leads together, destoying a good
> part of the leads and a signifigant chunk of a PC board, meanwhile my
> Tech put an electrolytic in backwards and shut it off when it began
> to sound like frying chicken.  A bad day, all around.  I'd like to
> still be watching sunsets when I retire.  These things explode and
> arc and spark, and a little polycarbonate lens between you and it may
> be crucial someday.
> -- Lawrence Lile

Just had an interesting idea that might be useful.  If you wear
glasses normally, make sure to get them with polycarbonate lenses.  I
always do, and it's saved my eyesight a couple of times.

If you don't wear glasses, why not get some?  I'm sure the lens shops
would have no problem making flat glasses; it wouldn't be hard.
They'd be a lot more comfortable than safety glasses, though not quite
as sturdy.  (However, polycarb normal glasses are pretty strong.  Got
hit once by a paperclip shot off a rubber band (don't ask) and it
didn't even make a scratch.)

-Ansel
ObPIC: does anyone have plans to a PIC programmer?  I've got quite a
well-established junk box, but no $$$ to make one.

It would be really nice if I can work with it in Linux.
--
GCS/CM/IT d- s+:-- a--- C++++ UL++++>$ V? P+++ L++(++++) E++ W+ N++ w---
M-- PS++ PE Y+ PGP++ t++(*) 5+++ X+ R tv b++++ DI++++ D---(+) G++ e*>++
h!>++ r--- y?

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...