Long and longer timeout periods are frequent goals for the ubiquitous 555 timer. Generally, this is accomplished (albeit unreliably) by unusually large electrolytic timing capacitors. However, here ...

The 555 timer is one of the most versatile integrated circuits available. It can generate PWM signals, tones, and single-shot pulses. You can even put one in a bi-stable mode similar to a flip flop.

A common problem with on-delay timers is the timing capacitor reset. Typical timers (555 included) rely upon both complete power loss and finite elapsed time to assure that the timing capacitor is ...