We added a light dependant resistor (LDR) poking out the back of the Monochron, and with a little supporting software we have auto-brightness control. The display backlight now smoothly ramps from dimmest to brightest according to the ambient light levels.
Hardware
Circuit:
Implementation:
Note that we wanted to have the LDR on the back of the unit for aesthetic reasons (knowing that making a hole in the acrylic case with hand tools was likely to turn out a little ugly), but doing that definitely made the re-assembly very difficult. In hindsight, I'd probably have used flying leads from the ldr to the PCB, so as to be able to tuck the LDR over the existing ISP hole.
Software
Building on Toine Ceulemans' amazing Emuchron:
https://github.com/bdlow/Emuchron/tree/autobrightness
