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.

Whenever I use the 555 timer, it seems that the output polarity is invariably incorrect, and the way the 555 functions, it normally cannot generate a duty cycle of less than 50% — 90% yes, 10% NO!