BeamHolophoner

Look only on the right of the red line. The left is a circuit the i used to play with the parallel port on my computer using Linux/C i turn the transistors on and off to control LEDs.

This circuit never made it off the breadboard. I got the idea while playing with the light-seeking head. when the head would lock onto the light source the motor produced a buzzing sound from the bicore switching faster than the motor could keep up. thus here i plugged in a piezo-electric buzzer from a pager in place of the motor and used a cadmium sulfide photocell to drive the bicore frequency. The brighter the light source the higher pitched the buzz. in complete darkness the buzzer pinged at about 1Hz, a few inches from a light bulb it goes out of the range of the human ear (~20kHz).