We found this circuit in a 70s RCA manual. The circuit uses an LDR by directly driving a sensitive relay. Resistor R1 is 5.6 ohms and R2 is 25k. The pot is 10k of wire.
This series sensor circuit is from 1995 Popular Electronics. The circuit can use any SCR and the...
The circuit is a multivibrator version using two NPN general purpose transistor. This circuit can...
This circuit is from 1976 documentation. It uses the operational amplifier 709 which is no longer...