UV exposure Unit

Up til now I have been making my own circuit boards at home with the toner transfer method, and while I have had some success it seems very hit and miss, and doesn't get amazing resolution. The toner is porous, doesn't always adhere well, can't be used for very thin traces, and is susceptible to melting and spreading out while being ironed on. I decided to upgrade my PCB making process to one using photo lithography. I bought some dry film photoresist sheets on eBay, but in order to have consistent results an ultraviolet exposure box is necessary. I designed, built and programmed this box, and am very happy with how it turned out, as well as the results I am now able to achieve with it. I used almost 500 UV wide angle LEDs emitting at 395 nm as the light source, and a handful of red LEDs mixed in to allow me to line up the masks and get things set up without prematurely exposing the resist. The power supply and timer/controller is in the box on the right hand side, as well as a lockout magnetic switch to only turn on the UV when it detects the box is closed. The indicator shows when the UV panels are powered on. The time may be easily entered using the keypad on top, and is displayed with four large seven-segment LED displays above the keypad. Buttons A through D allow commonly used times to be stored and recalled as presets using the microcontroller's EEPROM. If the lid is opened while the UV is on, the controller turns it off, turns on the red lights, and pauses the timer until the lid is closed again.

I've added the CAD files for my original design Here, and I have updated the schematic with the changes I mentioned in the comments, available Here. There's more than one new design for the display board, both use only 3 I/O pins and should drive the display with even brightness. The first one uses four 74hc595 shift registers, and four ULN2003 darlington arrays. If the high current 595 shift register variant is used, the darlington arrays can be omitted. The second version multiplexes the LED displays together, using only two 595 shift registers and one darlington array, and four BC558 PNP BJTs. This design saves quite a few parts, but may be slightly harder to write code for, and may be slightly dimmer due to the multiplexing. Either design should be better than what I have used in my old design, and the control board should also be compatible with the Sparkfun serial seven segment display, if you do not want to bother with building your own.