Circuit Timer Long Duration
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.