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'Prototyping technology (was: Re: PIC Prototyping b'
1998\02\05@080821 by Morgan Olsson

picon face
>You don't need an etched circuit board to make a small PIC circuit work.
>Nearly all of my prototypes are on perforated board (available at Radio
>Shack at astronomical markup).  It's low cost, infinitely rewirable, and
>usually has room for last-minute changes.  Good soldering skill is
>required.  If you don't have it, you ought to learn sometime anyway.

YES, this technology is very nice.

>Wire ground and power to all the ICs using #24 bare
>copper wire before installing any other wiring.  Put capacitors near the
>other ICs as needed (Sequential circuits, like shift registers, memory
>chips, counters, etc. definitely should have them).

Also keep the power and ground close and parallel. That reduces impedance,
and less capacitors needed. I use to route them along the ICs, either on
top side before mounting IC or IC sockets, or on the solder side.

>- Use wire-wrap wire for the signal wires.  Cut it to length, and strip
>1/8" off of each end.  Bend a hook in the end and wrap it tightly around
>the pin, then solder.  

I've found that take too much time. I use unisolated tinned 0.5mm copper
and a very fine bent plier to route the cirquit like normal tracks. No need
to bend around components pins! Use good solder (Multicore 399) and exact
control of temperature. One track between each IC pin is no problem,
sometimes 2 possible.
Take time though, before you got the skill, then it«s pretty fast.

Of course, most component pins except IC«s are long enough to just bend,
cut and solder. Very quick.

There is also those nice thin isolated wires that do not need to be
stripped; they strip themselves when heated!

After a while you will develop a skill to see both sides of pcb, and the
scematic at the sime time in your mind, so you are actually doing the cad
in this stage.

>Circuits made this way can be the same size or smaller than printed ones
>(of course, not if SMT parts were to be used) and quite durable.  It only
>takes a couple of hours, and no special materials, to make a
>one-of-a-kind circuit with 3 or 4 chips.

Actually theese kind of boards are exellent
1)      Very easy to reroute.
2)      Mechanically flexible.
3)      Can handle many times higher current. (I«ve used wires up to 2mm diam)

Therefor I sometines make small scale production on them.
Almost every special one-unit design have I made this way.

(Well small scale... The record is 1000+ of a small 15 components
regulator! There was not time to CAD and send to PCB manufacturer.
I can still make them in my sleep...)

To make SMT prototype:
1)      Print the SMT side of PCB on your printer. Use heavy paper sheet.
2)      Cover the PCB area with transparent double sided adhesive. (I use a 3M
3)      Use a needle to make holes to other side (if double sided PCB)
4)      Use very small pliers etc to route the whole side. I use 0.1 to 0.3 mm
tinned or silvered copper wires. I strip off the isolation from normal
Multi-core cables get them.
5)      Use a very narrow needle-style solder point to solder components.
6)      Route other side. If components on back side too, cover it with adhesive
tape there too before (3) above, but don«t remove adhesive«s protection then.

The prototype will perform much like a "real" PCB would!

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

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