This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4 LEDs flashes continuously at a speed given by C1 and the setting of R3.
The purpose of this circuit is to allow common analog multimeters to measure low resistances, on...
We found this circuit in a Radio Electronics issue from July 1969. The lamp remains on until C1...
This circuit was found in a 90s Popular Electronics. The sensor can be any phototransistor. ...