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'[EE] Image scanning'
2012\10\23@182908 by IVP

face picon face
Hi all,

I'm working on a project which involves scanning line drawings into
memory (a large SRAM). Ideally the images will be laser printed on
white paper, so the contrast will be good and lines should be sharp.
But other users may not adhere to recommendations, for a variety
of reasons, so I'm looking for components or techniques that will
reasonably cover all eventualities

My aim is to be able to resolve to 0.5mm or better. I've made an
X-Y bed, 600mm x 600mm (but I may well go bigger), with a
couple of steppers and threaded rod that has good positional
resolution, now I need a read head

Some things I hope to try ASAP -

Illuminate from the back with an LED with a opto sensor above the
paper. This would involve an extra mechanism for the LED to follow
the read head. No big deal

A reflective or proximity opto, which would bounce IR off the paper

Some lens system to enlarge the detection area

I've used these techniques for other projects but not with resolution
as the primary goal. Mostly for event detection. I expect I may have
to restrict a sensor's field of view (eg pinhole mask)

Any other ideas or experiences ? I keep daydreaming about cameras
but I don't think that's necessary, and I want to use components that
are cheap and repeatedly available. Even something like an optical
mouse sensor perhaps. Cheap enough to scavenge from a bought one
or pick up as broken

TIA

Jo

2012\10\23@183945 by Bob Blick

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flavicon
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I've used fiber optic cable for that exact purpose. You can use it for
both illumination and sensing. It's neat because it reduces the mass you
need to zip around. Back when I did it (1985?) you could just use a
fiber emitter and detector pair. Nowadays they probably integrate
electronics into them, which might get in the way of what you want to
do. But you could always hack together some way to couple fiber to an
led and a photodiode.

Cheerful regards,

Bob

On Tue, Oct 23, 2012, at 03:28 PM, IVP wrote:
{Quote hidden}

> -

2012\10\23@185327 by John Coppens

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On Wed, 24 Oct 2012 11:28:58 +1300
IVP <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:

> Any other ideas or experiences ? I keep daydreaming about cameras
> but I don't think that's necessary, and I want to use components that
> are cheap and repeatedly available. Even something like an optical
> mouse sensor perhaps. Cheap enough to scavenge from a bought one
> or pick up as broken

I think you'll be better off with a camera. In fact the only drawback
I can think of is speed. The camera will give you only tens of images
per second.

On the other hand, even a cheap camera could give you a much faster
'prescan' of the drawing and quickly detect where the actual drawing is, so you could skip white areas. Even a cheap webcam with bad optics
would work, as long as you use the same reference point for the precision
scan.

John

2012\10\23@185702 by IVP

face picon face
> I've used fiber optic cable for that exact purpose

Sounds interesting. I've got a short length of the plastic type, I
think it's 1mm inside a black sheath. Probably too thick

But we do have this fibre optic table lamp with lots of fine
strands, and no one's around ...... tiptoe tiptoe .... snip

Thanks

Joe

2012\10\23@185945 by Harold Hallikainen

face
flavicon
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> I've used fiber optic cable for that exact purpose. You can use it for
> both illumination and sensing. It's neat because it reduces the mass you
> need to zip around. Back when I did it (1985?) you could just use a
> fiber emitter and detector pair. Nowadays they probably integrate
> electronics into them, which might get in the way of what you want to
> do. But you could always hack together some way to couple fiber to an
> led and a photodiode.
>
> Cheerful regards,
>
> Bob

That's an interesting idea! Another idea is a photodiode for a sensor and
a laser diode for illumination. The laser diode would light a very small
area so you would not need much, if any, optics on the detector.

Harold


-- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!
Not sent from an iPhone

2012\10\23@190320 by IVP

face picon face
> I think you'll be better off with a camera. In fact the only drawback
> I can think of is speed. The camera will give you only tens of images
> per second.

Not particularly worried about speed, mostly because the processing
and eventual use of the image is comparitively very slow. Liken it to
downloading a two hour film in minutes. Whilst you're processing (or
watching) the first image, that time can be used to scan many more

Jo

2012\10\23@190504 by Bob Blick

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One thing you'll find out quickly enough - get the brightest LED you can
find and drive it hard. You need to drown out ambient light. Plus, the
more light you have, the faster and more accurate your detection will
be.

If you use an RGB LED you can sequence and scan color :)

Best regards,

Bob


On Tue, Oct 23, 2012, at 03:56 PM, IVP wrote:
{Quote hidden}

> -

2012\10\23@190634 by Denny Esterline

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On Tue, Oct 23, 2012 at 3:56 PM, IVP <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:

> > I've used fiber optic cable for that exact purpose
>
> Sounds interesting. I've got a short length of the plastic type, I
> think it's 1mm inside a black sheath. Probably too thick
>
> But we do have this fibre optic table lamp with lots of fine
> strands, and no one's around ...... tiptoe tiptoe .... snip
>
> Thanks
>
>
I don't think I have any really helpful suggestions, but you've peeked my
interest...

Can you better describe your application? 0.5mm resolution is really pretty
low
for most scanning applications I can imagine (600 DPI is about 10 times
better)
And scanning with an X-Y plotter.... And a single pixel pickup... 600mm
/0.5mm
1200 passes... at even 1 ms per pixel that's like 24 minutes of scanning...

And I know you're sharp enough to have already thought this... So if you're
still
looking for a solution, your application must be... Interesting :-)

-Denn

2012\10\23@190707 by IVP

face picon face
> That's an interesting idea! Another idea is a photodiode for a sensor
> and a laser diode for illumination. The laser diode would light a very
> small area so you would not need much, if any, optics on the detector

I have some IR laser diodes and optics from scrapped CD drives. It
would certainly add street cred if I could say the scanner uses lasers
and fibre optics !

Thanks

Jo

2012\10\23@192856 by IVP

face picon face
> If you use an RGB LED you can sequence and scan color :)

Ah, now that rang a bell

I dug into my pile of mags and found a Silicon Chip project from
June 2005 - "PICAXE Colour Recognition System"

It uses the TCS230 colour sensor IC and an 8-pin PICAXE,
probably a basic one (12F675 ?) given the date

http://www.w-r-e.de/robotik/data/opt/tcs230.pdf

http://www.edaboard.com/thread248427.html

Colour sensing isn't on the immediate agenda, and the IC perhaps
a bit coarse, but I thought I'd pass that on while I remember

Jo

2012\10\23@194953 by IVP

face picon face
> And scanning with an X-Y plotter.... And a single pixel pickup...
> 600mm /0.5mm = 1200 passes... at even 1 ms per pixel that's like
> 24 minutes of scanning...
>
> your application must be... Interesting :-)

Well, that's two of us who think it might be ;-)

It's part of an idea suggested a while back about burning cutting
patterns onto wood with a laser, primarily for fine bandsawing or
scrollsawing

The universal method presently is to print out the pattern and stick
the paper to the wood with contact adhesive. Cut the wood and
then remove the paper. It's quick, but glueing is a bit invasive and
can cause staining, plus you've got more sanding

The idea I'm trying is to scan the pattern, store the image, and then
play it back through a burner. Either that or have two X-Y tables,
one for reading, one for burning, just like you'd copy a CD, with
no intermediate storage. Although it's very easy to store a file so
not adding an SRAM would be short-sighted

I've tried it non-mechanically and it's certainly very doable, if slow.
For what I have set up here that's mostly due to the burning speed
of the laser. I am considering a small router with a fine bit to do
the drawing, pretty much a basic 2D CNC, but of course you'd
have to make sure any routing is done outside the line and that
would take s/w a little smarter than simple lines. Plus the size of the
bit (1.8mm I think is the smallest commonest carbide) limits the
resolution, but you'd pick the right jobs to use it on

Woodworkers are a mellow laid-back bunch. Even if a scan and
burn took an hour, that time can be spent on many other things in
the workshop, especially once you have the first item to work on

Jo

2012\10\23@200558 by Brent Brown

picon face
These chips came to mind... built in photodiodes (1x visible, 1 x infrared), ADC, drive external LED with programmable current (the Si1143 can drive 3 x LEDs independently).

http://www.silabs.com/products/sensors/Pages/default.aspx

-- Brent Brown, Electronic Design Solutions
9 Titoki Place, Pukete,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  brent.brownspamKILLspamclear.net.nz

2012\10\23@200743 by Isaac Marino Bavaresco

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face
Old automatic cutting machines used a line-following circuit to copy
directly from a paper print.
They cut using acetylene or plasma torches, and were completely analog,
no processors.

Isaac



Em 23/10/2012 21:49, IVP escreveu:
{Quote hidden}

> Joe

2012\10\23@201148 by Denny Esterline

picon face
On Tue, Oct 23, 2012 at 4:49 PM, IVP <.....joecolquittKILLspamspam.....clear.net.nz> wrote:

{Quote hidden}

Ok, interesting was the right adjective.. :-)

Some random thoughts...
If you want really small carbide router bits, the PCB industry uses some
down in the 0.020" range (about 0.5mm)
What you've described is basically a raster scanning operation, but, I'd
expect your laser marker/burner to
execute vector moves (raster is certainly possible... single pixel dot
matrix...) that's a non-trivial bit of conversion
math. Aside from the math, what you described above is about 1.5 Mpixels..
And storing multiple "scans"..
The whole thing suggests PC to me. A second hand PC, cheap web cam on a
stand with a good light,
Inkscape and some of the available plugins and you're about there.

Though I freely admit, I've used some "highly unconventional" solutions
before when the journey
was more important than the destination.

:-)

-Denn

2012\10\23@202829 by IVP

face picon face
> Old automatic cutting machines used a line-following circuit to
> copy directly from a paper print

There are two options for me to try

One is the simple X-Y complete scan, recording even white space.
That method would be the easiest, if less elegant, to implement

The other is line following. I'm sure if I think about it I could come
up with a method to do that. As you can imagine, scroll patterns
can be quite detailed and there could be many isolated lines for
holes etc

Both obviously need a read head, which is the mission du jour

For the second method, line following, off the top of my head
I might start with X-Y scanning until black is detected. Record
its position and follow the line. On completion, return to the
recorded position and X-Y scan again until the next black
detection. Record its position and track the line, etc etc

But I don't see how you could do this without recording where
the read head has been, to avoid multiple follows of the same
same line and detect false starts with the X-Y scanning

My intention was to X-Y scan and bitmap the page into SRAM.
I've a tray of 512k x 8 SRAM doing nothing. At 500mm square
by 0.5mm step that's only 1M bits

Joe

2012\10\23@205304 by IVP

face picon face

> Some random thoughts...
> If you want really small carbide router bits, the PCB industry uses
> some down in the 0.020" range (about 0.5mm)

Yes, I'd thought about PCB router bits. The catalogue I first looked
at was for a local bit supplier who makes them with 1/4 shafts for
standard hand routers. I expect PCB bits would work well on
wood if they can cope with GFRP. Perhaps a bit wary of hitting
a very hard knot though, which can cause even a big flute to burn.
I'd want only 1 or 2mm of the bit proud to avoid snapping as it
would be solid carbide and brittle

Wood of course is very variable. I've already found that to get the
best burn you have to jiggle the laser up and down very slightly to
compensate for any irregularities in the wood's surface putting the
beam out of focus. Possibly this could be done with a constant
vibration of either the whole burn head or the lens. A fine depth
gauge for the beam might be workable but it would be on quite
a small scale, although a coarse depth gauge would be needed if
the wood isn't perfectly flat overall

> The whole thing suggests PC to me. A second hand PC, cheap
> web cam on a stand with a good light, Inkscape and some of the
> available plugins and you're about there

I'm hopeless with PCs. But I do like to think I'm good at making
things from scratch and love my shed time

Jo

2012\10\23@212915 by IVP

face picon face
> The whole thing suggests PC to me

BTW, how's your computer desk ?

http://www.dailymail.co.uk/news/article-2221821/Filthy-home-offices-piled-high-cigarette-butts-beer-cans-make-commuting-living-room-nightmare.html

I now consider mine just a little untidy

Joe

2012\10\23@225635 by Denny Esterline

picon face
>
> > The whole thing suggests PC to me. A second hand PC, cheap
> > web cam on a stand with a good light, Inkscape and some of the
> > available plugins and you're about there
>
> I'm hopeless with PCs. But I do like to think I'm good at making
> things from scratch and love my shed time
>
> Joe
> --
>
>
I know the feeling. :-)

I've recently been playing with some CNC stuff. there's an interesting
video on youtube of
a dirt cheap machine cutting thin foam (6mm ish) with an oscillating
needle. Obviously
not a laser, but within some limitations, similar capabilities. I was
considering making
one, and I tripped on the EGGBOT... Really nice part about eggbot is it's
open source
HW and SW and they have a plugin for Inkscape (also free) that makes it
literally draw
line on screen, click plot and the steppers are moving.

Adding a couple new ideas to my "tool kit" has seriously expanded my "if I
had time" list.

-Denn

2012\10\24@034725 by IVP

face picon face
> I've used fiber optic cable for that exact purpose

Just to clarify, did you have two pieces of fibre, one to illuminate
and the other next to it as the detector ?

Jo

2012\10\24@043845 by alan.b.pearce

face picon face
> Any other ideas or experiences ? I keep daydreaming about cameras but I don't think
> that's necessary, and I want to use components that are cheap and repeatedly
> available. Even something like an optical mouse sensor perhaps. Cheap enough to
> scavenge from a bought one or pick up as broken

A linear sensor from an old printer port connect scanner? Most of these machines have minimal electronics in the scanner, and use smarts in the host machine.

If the idea sounds good, I would use an old XP machine with a printer port and logic analyzer to look at the signals and see how they clock the data out of the sensor.
-- Scanned by iCritical.

2012\10\24@045225 by alan.b.pearce

face picon face
> BTW, how's your computer desk ?
>
> www.dailymail.co.uk/news/article-2221821/Filthy-home-offices-piled-high-
> cigarette-butts-beer-cans-make-commuting-living-room-nightmare.html
>
> I now consider mine just a little untidy

Makes mine look positively tidy ... ;)))
-- Scanned by iCritical.

2012\10\24@062719 by alan.b.pearce

face picon face
Going OT from subject line, but along the lines of why the Op asked the question ...

3D printed band instruments ???

http://www.bbc.co.uk/news/technology-20047744

4 minute video of 3D Print Show in London recently ...


-- Scanned by iCritical.

2012\10\24@111149 by Bob Blick

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Yes, two pieces of fiber, one with a detector and the one with emitter.
I polished the ends, then tapered the outer sheath so they could be
bound together at an angle with their light paths intersecting (as best
as possible) at the scanning end. The fiber I used was fat, maybe almost
1 mm. I got scans that were fax quality.

The emitters and detectors I used looked sort of like the attached
picture but only had two wires each.

Friendly regards,

Bob
On Wed, Oct 24, 2012, at 12:47 AM, IVP wrote:
> > I've used fiber optic cable for that exact purpose
> > Just to clarify, did you have two pieces of fibre, one to illuminate
> and the other next to it as the detector ?
> > Joe

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2012\10\24@143915 by Sergey Dryga

flavicon
face
IVP <joecolquitt <at> clear.net.nz> writes:
>
> It's part of an idea suggested a while back about burning cutting
> patterns onto wood with a laser, primarily for fine bandsawing or
> scrollsawing
>
The way I see the objective is to print a pattern on a piece of wood, right?  If yes, then why not use an ink-jet print head (parallax used to have them while
ago, or "repurposed" one from a printer), and use your x-y table to print
directly onto wood?  Scanning can be done using regular scanner, camera etc.. Alternatively, a modification of an ink-jet printer to feed wood instead of
paper would make it easier to interface to a PC.  In this case, printing options
are practically unlimited, with the exception of blurring due to capillary
action of wood.
This might be not as interesting as the "cool" project with 2 x-y tables etc,
depends on your goals.
Sergey Dryga

http://beaglerobotics.com

2012\10\24@173346 by IVP

face picon face
> If yes, then why not use an ink-jet print head

Hi Sergey

I'd definitely thought of using a printhead. And daydreamed about
it long and hard last week when I was stripping down scrap printers

It's not out of the question. Each method has its pros and cons

For example red laser marks darker materials best (probably a
frequency match between red light and brown wood), printer marks
light materials best (pine, balsa, tawa etc), unless you use a colour
cartridge and switch from blue to yellow

It would be fairly easy to mechanically convert a desktop printer
to feed wood instead of paper. Scaling that to A0 might be tricky,
but still doable

Maybe a bit more daydreaming will help

Jo

2012\10\24@183211 by IVP

face picon face
> Yes, two pieces of fiber, one with a detector and the one with
> emitter. I polished the ends, then tapered the outer sheath so
> they could be bound together at an angle with their light paths
> intersecting

OK, sounds like a mini version of the reflective opto I tried first

The strands of my fibreoptic lamp are much thinner than 1mm,
probably simplest to mount them in fine holes drilled in a block
of metal. Why do I get the feeling I'll be shopping for replacement
bits some time this week ?

Thank

2012\10\24@192733 by IVP

face picon face
Thanks for all replies and suggestions

You'll understand if I try first with what I have to hand already.
Next time I do a Mouser or Digikey order I could have a look
at some of the specialised ICs

Thanks

Jo

2012\10\31@215249 by IVP

face picon face
> The emitters and detectors I used looked sort of like the attached
> picture but only had two wires each

Bob,

Over the past few days I've tried various methods and think I've
decided what will be best for my application

First thing I tried was a standard reflective opto, OPB702. OK,
but coarse resolution, even when restricting the apertures and using
matte laser printing on shiny paper to give it the best contrast

So I made my own reflective sensor with 0.1mm optic fibre + IR
LED and an optic fibre channelling the reflection to an RPM1700
IR receiver. OK, fussy to set up and still coarse resolution

>From The Drawer Of Parts That'll Come In Handy One Day came
a Siemens SFH551V fibreoptic housing, like the one you posted,
complete with a couple of inches of 1mm plastic fibre. Same result
as before unfortunately

But it was easy to do a quick test with light transmitted through the
paper, and it worked very well. I'll make an adapter to use 0.1mm
fibre. I'm assuming the RPM1700 will work equally well. It seems
to be a lot more sensitive than the SFH551V, which may or may not
be an advantage

This means a sheet of glass with the IR receiver on top tracked
by an IR transmitter below, something I instinctively thought from
the gitgo might the most reliable. A little bit more mechanics but
not a big deal for getting a better result

Jo


'[EE] Image scanning'
2012\11\01@110012 by Denny Esterline
picon face
> This means a sheet of glass with the IR receiver on top tracked
> by an IR transmitter below, something I instinctively thought from
> the gitgo might the most reliable. A little bit more mechanics but
> not a big deal for getting a better result
>
> Joe
> --
>
>
At that point it would be interesting to see if you really needed to
have both the emmiter and detector track on the X-Y scan.
May be able to move the detector along the top and simply
illuminate the entire bottom of the page with IR....

Actually, depending on environment, users, and the type of
glass you use for the bed, it may be better to put the detector
under the glass to keep it cleaner. Obviously that increases
the distance between the page and the detector, so it may
have resolution consequences.

-Denn

2012\11\01@114600 by Bob Blick

face
flavicon
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Hi Joe,

What I remember is the most important thing for detail is to get the
fiber as close to the subject as possible. Since there is no focus, it's
like a contact print. With your OPB702 reflective sensor, it probably
has a molded lens with a definite focal point where it will work best.
You might try adding additional illumination, at least temporarily, to
figure out where that focal point is.

Friendly regards,

Bob


On Wed, Oct 31, 2012, at 06:52 PM, IVP wrote:

{Quote hidden}

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2012\11\01@123908 by alan.b.pearce

face picon face
> > This means a sheet of glass with the IR receiver on top tracked by an
> > IR transmitter below, something I instinctively thought from the gitgo
> > might the most reliable. A little bit more mechanics but not a big
> > deal for getting a better result
> >
> At that point it would be interesting to see if you really needed to have both the
> emmiter and detector track on the X-Y scan.
> May be able to move the detector along the top and simply illuminate the entire
> bottom of the page with IR....
>
> Actually, depending on environment, users, and the type of glass you use for the
> bed, it may be better to put the detector under the glass to keep it cleaner.
> Obviously that increases the distance between the page and the detector, so it may
> have resolution consequences.

My thought would be to use an LED under the glass without fibre or lens, so it is illuminating the area the fibre is looking at without having fibre alignment issues between the sensor fibre and the illumination fibre. The sensor will still need some form of spot sensing focusing to get the required resolution, whether this is done by fibre of lens will be up to the implementation.
-- Scanned by iCritical.

2012\11\01@170136 by IVP

face picon face
> At that point it would be interesting to see if you really needed
> to have both the emmiter and detector track on the X-Y scan.
> May be able to move the detector along the top and simply
> illuminate the entire bottom of the page with IR....

It's not too difficult for the top and bottom elements to track. I've
worked out a mount which supports the glass and allows a U-shaped
arm to go underneath. The bottom drive is passive, driven by a gear
connection to the active top drive

However ....

I tried the fibre with an IR receiver from a VCR. These ubiquitous
Sharp cans are so sensitive that even with the only port of entry to
the amplifier being the 0.1mm diameter fibre, it will still respond to
a remote control pointed in just about any direction. So flooding the
underside of the image may very well work, er, very well

The alternative is the tracking system with localised (ie focussed)
low power IR

Experiments ensued

Joe

2012\11\01@172635 by IVP

face picon face
> My thought would be to use an LED under the glass without fibre or
> lens, so it is illuminating the area the fibre is looking at without
> having
> fibre alignment issues between the sensor fibre and the illumination
> fibre. The sensor will still need some form of spot sensing focusing to
> get the required resolution, whether this is done by fibre or lens will
> be up to the implementation

It's a definite improvement if the fibre isn't right to the end of the sheath,
otherwise scattered light from wider angles (ie fuzzy resolution) enters
the end or side of the fibre. That goes hand in hand with the sensitivity
of the amplifier

Joe

2012\11\01@172656 by IVP

face picon face
> With your OPB702 reflective sensor, it probably has a molded
> lens with a definite focal point where it will work best.You might
> try adding additional illumination, at least temporarily, to figure out
> where that focal point is

The datasheet says 0.15", which is what I set the guide to, and it does
seem to be its sweet spot. That particular opto might work if a Schmitt
Trigger or PIC smarts was added, as it's not too definite on edges or
thin lines. Think I'm veering towards through-paper though

Jo

2012\11\01@201830 by Richard Prosser

picon face
Joe,
The IR receivers used in TVs & VCRs etc are sensitive to modulated IR. So
to get a good response  from your sensor you may need to apply ~36kHz (can
vary with manufacturer/system) on-off modulation to your emitter. This may
also limit your detection speed depending on scan speed and resolution.

RP


On 2 November 2012 10:18, IVP <EraseMEjoecolquittspam_OUTspamTakeThisOuTclear.net.nz> wrote:

{Quote hidden}

>

2012\11\01@204619 by IVP

face picon face
> The IR receivers used in TVs & VCRs etc are sensitive to modulated
> IR. So to get a good response  from your sensor you may need to
> apply ~36kHz (can vary with manufacturer/system) on-off modulation
> to your emitter. This may also limit your detection speed depending on
> scan speed and resolution

Hi Richard,

yes, apart from the simple optos, I use modulated 38kHz

http://home.clear.net.nz/pages/joecolquitt/irtx2.gif

A second 555 drives Data In with a known frequency so it's easy
to spot a bona fide signal

Jo

2012\11\01@214602 by John Ferrell

face
flavicon
face
I don't think any mechanical scheme will come close to a flying spot scanner (crt) in accuracy or speed.
Raster scanning is also self limiting. However, all of the Laser printers I am aware of are raster printers so anything tighter that that is wasted.

On 10/23/2012 6:28 PM, IVP wrote:
{Quote hidden}

-- John Ferrell W8CCW
“The greatest lesson in life is to know that even
fools are right sometimes.” Winston Churchill (1874-1965)

2012\11\24@025356 by IVP

face picon face
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> I think you'll be better off with a camera

After trying a few low-tech methods I think you'll be right

My idea was to try and detect down to a 0.5mm black line, using
either through-paper or by reflection, but the variables make it just
too fussy to be consistent. I tried quite a few combinations of
illumination methods, with red/IR (LED and laser), optic fibre,
high- and low-gain detectors, lenses, masks .....

So yesterday I started looking at cameras. A local store has USB
webcams for $10, which I could hack, but I'll plump for the Game
Boy cameras that have been sitting on my shelf since 1999 (an Out
They Go special, $5 each). Uses the Mitsubishi Artificial Retina IC.
At the time I downloaded a pile of paperwork on it, which will at
last come in handy

Would not want the designer of this site picking my decor

http://gieskes.nl/gb_camera_video_out_tutorial/

Isn't that just awful ?

> In fact the only drawback I can think of is speed

The nice thing about this IC, a 128 x 128 grey-scale sensor, is
that you can clock it with the micro. That might not be the case
for a full-colour webcam. So in theory all I need to do is find
out the physical size of a frame which gives me the detail I need
and move the camera in steps that big, processing just one frame

The datasheet says Data Clock period is 2us min, so that does
seem to imply the fastest frame data read time is about 3.3ms.
That's not too bad if a frame covers a reasonably big block of
the diagram. If it took a, say, 25mm square that'd make for a
pretty quick scan. Have to see what the included lens is like
and test out a few grid patterns. The IC also has an enhancement
mode to highlight edges, so that should help make the s/w a bit
simpler

Joe


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2012\11\24@033832 by IVP

face picon face
BTW, one other part of this project was to find a proper speed
control for my scrollsaw and bandsaw, both of which have
permanent split capacitor synchronous motors. I tried dimmer-
type controls but the loading affects the speed too much

I can heartily recommend this

http://www.jaycar.co.nz/productView.asp?ID=KC5509&keywords=kc5509&form=KEYWORD

That's retail, refer to http://www.electusdistribution.com.au for trade
or on-line

AIUI Jaycar has representation in the US, UK and Canadia. It
should run on 120VAC rather than 240VAC as there's no feed-
back from the HV side to the LV side. Maybe an adjustment
here or there to reference voltages. I can ask

The kit is based on a dsPIC and STGIPS20K60

http://www.st.com/internet/analog/product/243135.jsp

Output is single- or 3-phase mains voltage at a frequency variable
from 0 to 75Hz. I've added a footpedal and footswitch as well as
the panel controls

Another advantage of speed control is economy, and the controller
has a setting specifically for pool pumps

I quote and paraphrase from a letter in the November Silicon Chip,
which you'll probably find interesting

"Our pool pump is rated at 1HP and measured 922W when running
without the speed controller with a supply voltage of 241VAC.Using
a tacho I measured the speed at 2800rpm.

Using the Induction Motor Speed Controller I set the speed close
to 2000rpm (a little over 70% of full speed) and this resulted in a
wattmeter reading of 410W.

922W x 6 hours daily = 5.532kWh x 34.419c/kWh = $1.904
per day x 95 days = $180.90 per quarter

410W x 6 = 2.46kWh x 34.419 = $0.8467 x 95 days = $80.43

A saving of $400 per year, the kit paid for itself

The motor runs more quietly, barely gets warm and the filtration
seems to be unaffected"

Joe

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