To start, I had to make the array permanent and to such dimensions so as to have even lighting all over the surface of a typical photo-resistive PCB. So I laid them as shown, taking into account the distance of the leds which was enough to have overlaping beams of all leds. (so no blind spots where created) .
This was put in a ikea FIRA box, slightly modded for the purpose. (I left only the bottom drawer, didnt put the mid panels and used one of the mid panels as a swing door, attached to the top of the box with safety belt ribbon, glued and stapled to the box and door)
The first test consisted of burning two photoresistive boards with components needed to make MIDIBOX sequencer v3.3 . It was a total success. as it can be clearly be seen.
Before going into burning the midibox sets , I performed some tests. The results were as such.
* With the current setup (35 UV leds (UV =395nm) at about 20mA each from a distance of around 30cm) the board needed around 15 minutes to be developed
* Reasonable results were between 10 and 20 minutes
* The film used was simple inkjet transparency but I would print it TWICE (my printer is accurate enough) or use two printed transparencies one on top of the other
They were then developed using the standard procedures (NaOH in water for removing excess photo resist and then FeCl3 or Sodium persulfate or whatever you are used to)
The results were AMAZING. The Oven was (and still is) one of the most important tools in my “lab”. (The timer was dumped, I had a watch and pulled the plug)
PS. The array of leds needed quite a lot of current/voltage and I was lucky to find a hewlett-packard printer transformer with 1A/37V output.. Don’t test THAT with your tongue!