long duration timer circuit

Long Duration Timer

In order to create a long duration timer the 556 IC teamed up with a binary divider can provide delays as much as 16 times that set by the time constant of the first timer. You can use two 555 ICs instead of the 556.

The first timer provides a delay of 7.5 minutes and the divided outputs give a delay of 15 min, 30 min, 1 hour and 2 hours respectively. The second timer is used to obtain the desired output pulse length. Additional dividers may be added to give longer delays.

If you need a longer duration, for up to 10 hours you can use this circuit

Schematic of the Long Duration Delay Circuit

long duration timer circuit

Period = 0.7(R1 + R2)C1
Output Pulse Width = 1.1 x R3 X C5


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