Homebrew PCBs

Volkan Sahin wrote:  
> Thanks. I'm working on rotating mirror, I've one scanner unit removed
> from laser printer. 


What is the time performance off your machine? Maybe you gave that
information on the uploaded files but i don't have access sorry.

Comparing your printing time to process off printing a mask, align on
pcb and expose is it longer even with small boards??

Was recently discussed here various ways to raster scan the laser,
mirrors, prims or rotate/shake the laser. But the precision work needed
to accomplish this worth the time improvement for small boards?

>From your schematics (thanks again for posting) the servo is driven by
the mcu and the quadrature decoder and position counter is on fpga. Do
you thing the machine mechanics will handle faster speeds? Because if
all the servo drive be on the fpga i guess the speed could be improved.
I realise that will be needed a big logic to make it maybe even more
complex than the common signal and printhead part. But the laser
assembly will the one you already have.

For the rotating mirror i see some difficulties. The rpm speed has to be
low enough as film sensitivity. And it's divided by the 6 mirror faces.
>From the values from Adam Seychell and some lost on mirror and lenses
maybe the rpm needs to be as slow as 100rpm. And maybe the mirror won't
be accurate enough at this speed. But don't know.
>From a fast look to the driver datasheet i didn't get relation between
external clock and rpm.

In laser printers surface photo effect is incredibly sensitive so it has
very fast scans but photoresists need more energy. And these optics sure
have laser power limits they can handle.

I sincerely expect you start selling you board soon. But i still got the
servo driving with fpga idea. Your board don't have more IOs for it but
there are things like ebay 280420650046 and the same seller has a nice
arm board too (i have other one). So please from you experience can the
mechanics allow more speed?


PS
Just more one long email from me BUT! I started writing this email
almost 2 hours ago because something hit my mind in between. Few days
ago on emc2 list someone asked if he could use vga port to drive the
servos drivers. And i start wonder if we could use the hsync signal for
raster sync and vsync for line step. Ok i am crazy its a fresh idea, but
has some potencial.
The laser is connected to one color and the others can be used for other
information. No fast realtime uplink signals needed. The problem is only
synchronization between the hsync and mirror position. This has to be
handled by external circuit. The hsync is much longer than the dot clk
and that is a problem too. 
Imagine you have a full screen software with the normal software things
on top and on bottom the line to rast scan repeated more than 100 times.
All the lines on top will be used give time to the external circuit to
synchronise hsync with the 'zeroing' light sensor. At hsync any laser
signal is instantly blocked and a short pulse is given to laser as long
as the dot clock. If at that pulse the light sensor gets it so it's
synchronised if not the clock in the mirror driver should be modified
(maybe start fast and reducing rpm until synchronisation).
The circuit also has to block laser signal if no synchronisation. Know
in which line it's the raster lines and count successful rasted lines.
At 60hz or so vsync gives enough time to any cnc software to check if
the successful rasted lines are correct and move to next line.

Ok don't bother reply if not worth it.