Timer with Transistor Circuit

The below Simple Timer with Transistor Circuit Diagram is a simple timer that uses only two Darlington transistors and a capacitor base to generate a delay. When SW1 is pressed, the timer starts, the time setting is set by VR1. The duration of the timer is given by the values ​​of the potentiometer VR1 and the capacitor C1 that this circuit is 220 pF. To reach other durations of time must change the values ​​of these two components.

Timer with Transistor Circuit Diagram: