If an LED pilot lamp is used in battery powered circuits, it will unnecessarily consume power. This circuit lights an LED at power on and after one minute it will turns off.
The circuit uses a Zener diode and a switching transistor T1 to make an ideal power on indicator. The LED indicator turns on when the gadget gets power and gradually turns off after one minute. This save lot of power in battery powered gadgets. When the circuit gets power, LED turns on since the base of T1 is negative. C1 slowly charges through R1 and when the voltage level in C1 rises above 4.7 volts, Zener conducts and the base of T1 becomes positive. This makes T1 off and LED extinguishes. The charging time of C1 determines the on time of LED. This time can be increased or decreased by changing the value of R1 or C1. C2 helps to turn off LED slowly.