Parts for my Beseler-Minolta 45A Enlarging Head are getting difficult to obtain.  With this in mind I designed a LED enlarging head using the BasicX BX24 microcontroller to replace the Minolta.  

In order to power a string of LED's it's necessary to boost the voltage to accommodate the forward voltage drop of each LED.  To insure that the brightness remains constant a "current controlled" source for each string of LED's is also necessary.

I had the prototype boards shown below burned to house the BX24 MCU, a simple switching power supply, current controllers and molex 0.100" interconnects for the buttons which increase or decrease the intensity of the LED's and to the Hewlett Packard (now Agilent) display.