Homebrew PCBs

patroclus04 wrote:
> Hello,
> 
> I just got two 8W blacklight tubes, and have build some kind of
> exposure stand. I put the tubes on the bottom, facing up, and 7 cm
> above there is a transparent 0.5mm crystal. On top of it, it will be
> the PCB, facing down, with some weigth on it. Do you think this will work?
> 
> I just find some problem with this approach:
> - No reflector, is it really necesary?
> - Maybe 7cm is too close to the blacklight tubes... I really don't
> know if it will be done in 2 minutes, or 6. But anyway, is it too close?

Put a sheet of white paper over the glass and see how bright it glows in
the dark. If you can see bright bands because of the tubes being too close
to the glass, you should put in more tubes, or move them further away. Four
tubes 5-10cm away from the glass should be ok. Two widely separated tubes 5cm
away probably won't be good. Use a diffuse silvery surface behind the tubes
to make the thing a bit more efficient.