Homebrew PCBs

>> roel_cnc wrote:
>> i like the idea of making me own laserplotter.
<SNIP>

I like the idea too - so am going to try recreate
something half way between the pico-systems one
and the one bungard are selling.

> Adam Seychell wrote
> Are you talking a rotating drum laser photoplotter ?

Only sensible way to do it.

> Any idea of suitable low cost (<$5 A3 sheet) red
> light photosensitive film ?

Have just found out I can get some red sensitve film
for about <$3 AUD an A4 sheet. (<$6AUD for A3 if that
is close enough to the mark for you Adam)

<SNIP stuff about other colours>

> At say 20um wide pixel, that gives 15000 drum
> revolutions to scan a length of 300mm.  If drum
> spins at 1000 RPM, thats 15 minutes to complete,
> which is acceptable.

I can't remember the last time I did a board 300mm
wide.  So at 1000 RPM I reckon I would only be
waiting 5 minutes.

Still - I would be happy at 1 hour to get a decent
density to my blacks.  In fact having it take an hour
would be an avantage to me - it would make me check
for mistakes more thouroughly :D

<SNIP stuff about mechanics>

> Would be interesting hearing ideas too.

I have started having a go at it.  Have put together
a board with a 74HCT4046 Phase Lock Loop and some
other stuff to multiply the encoder wheel from a
servo motor. (and an ATMEL - apparently its against
the law these days to build something without either
a PIC or an Atmel on it)

Worked out my 7x10 minilathe isn't big enough to turn
up the drum.  Going to have to steal a mates lathe for
that.

Have speced/thought out an interface to dump a BMP
file from a PC out to a laser (synced to the PLL
above)

Two parts I have not thought through yet are the
laser diode driver circuit and the carraige for the
laser.

Laser diode driver might end end up being an off the
peg solution so should not be too hard.

The carraige however I am undecided on.  A belt, a
coach screw or a ball nut.  The $1000 for a ballnut/
screw does not scare me too much.  However if any
of the other homebrew guys out there want to make
one it might be a silly choice.

Whats everyone elses idea ?

Also do people want to see what I have done so far ?