Found in a 90s Popular Electronics, this sensor operates by infrared reflection. The components are modern, and the phototransistor can be of almost any type.
This very high input impedance circuit is suggested by Texas Instruments. The circuit can be...
We found this circuit in the August 1994 issue of Electronics Now magazine. The circuit is based on...
This bargraph circuit using LM3914 was found in the October 1980 Radio Electronics magazine. Note...