Delay off circuit using LM393 like voltage comparator PUBLIC

Close SW1 to charge C1. When SW1 is opened, the LED will remain lit for 60 seconds until C1 charge falls below Vref

Experiment using a voltage comparator (such as a TI LM393 component) to provide power to a resistive load (LED in this circuit) for a fixed period of time (60 seconds here) before the power is dropped. This circuit demonstrates the concept using an LED, but by attaching the output of the voltage comparator to an NPN transistor and then to, for example, a 5v relay module (that has some inductive kick protection such as a flyback diode), higher power devices such as motors or fans can be driven. Additionally, the circuit could be enhanced to allow for variable delays by replacing R2 with a potentiometer.

The simple operation of this circuit is contained in the Summary above.