Light

   Simple PIC circuit to monitor light.

circuit-sketch       fleXYcad-text (as above)  or  pcb version    PIC-code

See the full description here.

The opto-circuit is sensitive enough to easily detect the green glow of a Newton MP2k screen. Here's a fleXYlog 'scope
plot of a Newton backlight being switched on and off. The PIC circuit is sending data at 1200 baud to a Newton MP2k with fleXYlog running in landscape mode, and the opto-sensor is held closely to the MP2k screen.
The image was beamed to a MP100 and transferred to a PC using Newton Connection 2.0 utility software.