This circuit can keep a set of lamps on for up to 1 minute, time given by C2 and R2 that can be changed. The load depends on the relay. The circuit is old, from 1988 documentation, but totally viable today.
This is another quick adder that we found in an Electronic Design from the 80s. It also applies to...
The idea of this circuit is a resistance meter or continuity test with a common microammeter or...
This circuit turns off after a time that depends on C1. The circuit is from an Electronics Now...