This timing circuit was found in old documentation. The technology is CMOS. The supply can be made with voltages from 3 to 12 V. The time depends on R1 and C1.
The circuit shown is based on the LM101A; diodes can be replaced with equivalents. Resistor R1...
With the disappearance of the light falling on the LDR, the relay closes its contacts by...
We find this circuit in an American 1980s documentation. Modern equivalent integrated circuits can be...