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LED's and PCB's and why the sky is gnillaF



 
 
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Old April 13th 06, 11:22 AM posted to rec.aviation.homebuilt
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Default LED's and PCB's and why the sky is gnillaF


...Everything came out BACKWARDS! ...half a dozen of you said, some angrily, others with vigor.


They were the adventurous folk who read my post about using a laser
printer to make circuit board masks and actually tried it. The point
they missed was the bit in the article where I pointed out that with
this method you were working with a POSITIVE image.

Transfer a positive image to your copper-clad circuit board material,
the result is a MIRROR image (as opposed to a negative image). If you
want to end up with a positive image (and in this case, you do) then
you need to START with a mirror image.

Which is pretty easy to do, assuming you've used a simple CAD program
such as DeltaCAD, to create your mask. That is, you do the lay-out for
your circuit board then simply flip it over. Everything is now
reversed... except for the LETTERING. (Like all good CAD programs,
when you flip the drawing of a floor plan, a wing rib or whatever, the
software is very careful to preserve the lettering. I assume the High
Priced software allows you to select the orientation of your letter;
with DeltaCAD, what you see is what you get.)

So how do you end up with the lettering and numbers going the right
way? You start with a mirror image font... and type everything in
BACKWARDS. Yeah, I know... kinda wacky. But it works, as you'll see
on the circuit board masks once I post them.

So where do you get a mirror image font? Well... you can always make
one, which is what I did, 'way back when I was making fake antique
astrolabes and other 'ancient' instruments as up-scale decorator items.
Of course, the characters I was making were from languages that no
longer exist, in some cases. Which is why I had to create the fonts.
And then do it in a mirror image so the etching masks I was generating
with a laser printer would come out with the characters facing the
proper direction.

But if we're talking about circuit boards and a modern language, I
assume you can buy a mirror image font from the folks who sell such
things, since creating a circuit board mask using thermal transfer
isn't exactly new.

Once you have mirror image font in True Type format, if you have
Windoze you simply add it to your file of other fonts. ( DeltaCAD
allows you to use any font in the Windows font file.) Thereafter, when
you make up a circuit board mask, when you're ready to add the
nomenclature, you call up your mirror image font and simply type the
words in backwards, DER for 'red,' NEERG for 'green' and so on. Hold
it up to a mirror and that's what your circuit board will look like
after it's etched... assuming you're using the thermal transfer method.

-----------------------------------------------------

I'm sorry if your printing came out backwards but it shouldn't have any
impact on how the circuit board works. But I got the impression that
several guys reversed the whole circuit, a fairly common problem the
first time you try the thermal transfer method. Just go back to your
CAD program and flip it over. And erase any nomenclature. What you
want to see coming out of the laser printer is the image of the circuit
as seen looking down through the circuit board, as if you had xray
vision.

-R.S.Hoover

 




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