This circuit is based on learning of the discharge and charge of the C. This can be used as a timer circuit and can be applied in the OFF electrical appliances.
The application has also put relay instead of LED can be enabled.
This circuit is working as video below:
How it works
When we press the switch S1. It causes LED1 is light told state ready.
Then, we press S2, which is a timer switch. On press switch S2 current will flow to the C1 charge fully.
Then, to discharge out through R2 to limit current. To flow to the bias for transistor Q1.
Both Q1 and Q2 work together to Darlington Compound mode. To increase the current higher gain to drive the LED2 light up.
The LED2 is still overtime as C1 discharge all Q1 and Q2 stops LED2 is off if you want the timer circuit is longer. Then add the C1 and if you want a little time. to reduce it to C1.
10 Second Fan ON Delay Timer circuit using transistor
A friend of me wants 10-second delay timer circuit at can turn ON Fan 12V at use in an automobile. By fix the period of time about 10 second. He sets conditions that must use electronic part economize and seek easy with.
I then choose transistors and relay be control electric fan equipment follow the circuit in a picture. The value delays can fix with R1 and C1 which there is a formula calculates 0.5 x R1 x C1 .
When press S1 wait for about 10 second relay then work turn on give the electric fan works. The detail is other see in the circuit.
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