I was looking around for a DIY exposure unit, because I almost never got perfect results with the Toner transfer method. I used photopaper, backing from vinyl film (worked even better than the photopaper) and Press n Peel (which was probably the best, but quite expensive).
So I've decided to built my own UV exposure unit to keep the costs down to the minimum and get a good unit I can use for a long time.
It is based on Arduino Atmega328P MCU, with over 430 UV LEDs
The PCB board is made using Toner transfer method and isn't perfect. It was just too big and I was too lazy to do it again. However, marker here, scratch it there and it it good enough.
The unit itself is on single sided copper clad board, no additional cables, no narrow paths (axcept for one for power on the MCU). Design is straight forward. It's designed to be powered from 12V source (computer) and take around 2,7Amps @ full power which means around 30Watts.
Functions: Timer from 0 - 60minutes. You can set minutes and / or seconds. Brightness (driven by PWM) from 1% - 100% duty. Start / Pause / Reset, adjusting time / brightness at Pause without resetting the time.
The time is saved on start to the EEProm and loaded on reset / reconnected power. Found it handy, because once you'll find the correct settings, it will just remember it and reload it before every use.
The code isn't neath, but working perfect. I wrote first version in about 2 hours, it worked and thats how I left it. The 6pin header is FTDI compatible and you can use Arduino or any USB to TTL serial adapter
The LEDs were bought on eBay for 30€ / 1000pcs. I still have over 500 of them left if anyone is interested (I'm in Ireland).
MCU is Atmega328P, and other parts are just stuff off the shelf (Iguess around €5 - €10 cost)
Coper clad board was €8 from Maplin. Total cost cca €30.
If you want, you can ommit the electronics, and use just 12V to power it.
The unit itself is working like a charm and a pre-sensitised board is done after 3 minutes at full power. Thats good enough for me :)
Schematics as png:
Link for eagle files and source code for Arduino IDE
LED Unit - Google Docs