You know the working of 555 Timer and a number of circuits using the IC 555 are available. But I am experimenting with this unusual design. It will give more time delay than the usual 555 Monostable design which gives only maximum 3 minutes. See the trick.
The time delay in 555 Monostable depends on the values of the timing resistor connected to its Threshold pin (pin6) and the timing capacitor to its Discharge pin (Pin7). Usually, the capacitor is connected to the discharge pin and ground to discharge its stored current through the discharge pin. The time taken for discharging the capacitor determines the time delay.
Just reverse the connection. The timing capacitor is connected between the positive rail and discharge pin. So the time delay depends on the charging of capacitor. It will take 6-8 times higher than the typical Monostable. Got the idea. I got it while reading the properties of 555 timer.