Homebrew PCBs

>> Roel CNC wrote:
>>
>> i like the idea of making me own laserplotter.
>> tested: a pointerlaser (some cheap thing)
>> with an extra focus lense, a red sensible
>> film gave me super fine lines (close to a
>> single cloth fiber).
>>
>> did any of us fouling around with this idea !!
>> 
>> tips and suggestions always welcome:)
>> 

> Roel also wrote:
> Hi all, 
> M i started this toppic - got lots of replys
> on it with ideas :)
> 
> i gonna use Cunningfellow's pll thing some
> stepper for the laser and a dma-16 card -
> high speed dio card up to 250kB/s some code
> compiled (TPascal)that eats the the 274 (gerber)
> files and output to the drum

Roel - I have done a bit more work on the PLL
thing.  That one posted so far was just a test of
concept / prototype.  There are a few things
un-needed and a few other things that are needed.

It was built to do some tinkering with a
commercial DC servo motor I had lying around.
I finally want to just use a DC brushed motor
with some optos ripped out of mice (to make it
easier for others to get parts to build)

Also - I was planning on getting the data out of
a USB port (via an FT232) instead of some custom
hardware in the PC (again ease to duplicate).

The FT232 can do 4 Mb (which is same ballpark to
250 KB).  However if you compress the 1000dpi
data even with a simple algo like G3 fax you can
fit the data stream down 100 kilo baud (assuming
1000dpi and 10" x 10" board in 10 minutes)

I have sourced some toothed belts and linear
shafts for moving the laser head.  I have also
found a source of cheapish lasers that can be
focused down to small enough dot size if I can't
find a simple repeatable solution for people to
do the same with a cheap laser pointer.

Very interested in your thoughts on the carraige
part.  You seem to have a lot more experience
than I with CNC things (and PVC etch tanks).  Do
you think at 1000 (or 2000) DPI that there will
be a sticktion problem?  Do you think the tooth
belt idea is going to be good enough or do you
think that I might need to use a very fine pitch
leadscrew?

I have done some software on the PC to read a
BMP file compress it and send it out to my
hardware.  I was just going to use and external
gerber to BMP thing.  However - I have no
objections to reading geber directly if you would
like to work together on the project.

The only other though I had from the PC side
was to maybe write a GDI driver.  That might be
a bit out of my league though.

andrewm (or cunningfellow to some)