555 Timer Circuits

LOW FREQUENCY OSCILLATORS Circuit

If the capacitor is replaced with an electrolytic, the frequency of oscillation will reduce. When the frequency is less than 1Hz, the oscillator circuit is called a timer or "delay circuit." The 555 will produce delays as long as 30 minutes but with long delays, the timing is not accurate.

555 Delay Times:
C	R1 = 100k R2 = 100k	R1 = 470k R2 = 470k	R1 = 1M R2 = 1M
10µ	2.2sec	10sec	22sec
100µ	22sec	100sec	220sec
470µ	100sec	500sec	1000secThe following circuits show a 1-5 minute timer and 10 minute timer: