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.
We found this circuit in an American 80's documentation. The circuit can be adapted to function as a...
This 80's circuit, suggested in Texas Insrtruments documentation, uses a Hall effect sensor. The...
This interesting benchtop circuit was found in the May 1977 issue of Radio Electronics magazine. The...