10 sec to 30 min Time Delay circuit with relay transistor

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.

30 minuts transistor timer circuit

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.

10 Second Fan ON delay time using transistor

Buy components in this projects HERE!

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  1. Abel

    I would like to know if I can you this circuit and would like a delay (LED on for 60 minutes) If I can use a bigger condenser and only one transistor?
    thanks !

  2. suma

    sir,i’m not getting the output
    please help me

  3. Hi,Abel
    Thanks for your feedback.
    Please try to replace C1 with 220uF capacitors.
    It may times is 60 minuts as you want I am sorry that never test it with this value.

  4. Hi,Suma
    Thanks for feedback.

    Please check circuit again on breadboard, such as lead of transistor or capacitors. Please slow… check. This circuit works great.

  5. Daniel

    Hello, what if I want to add a small 5V relay, and power the circuit from 5V?

    I would place the relay at led 2 position, including a diode across the coil.

    Would this work?

  6. Thassim

    can we use 12 volts instead of 3v and change value ofR1

  7. Kav

    If 12V is used, will it change the 30 min to a shorter time? Thanks.

  8. Storm

    This won’t even do 30 seconds let alone 30 minutes.

  9. Kav

    This circuit works although you may have to play with the capacitor values and resistor value at the base of the transistor. I got a different time for the same values.Also make sure your capacitor and transistors are working properly.

  10. Kav

    My question though is, if you push it and let go immediately versus push and hold for a few seconds and then let go. Will it make a difference in the time?

  11. Kav

    Ok so I found out when you push and hold the button for a few seconds and release, the timer goes even longer. Is there a way to make it the same time when you push and hold vs push and release? Thanks.

  12. lamrin

    Need for adjustment timer
    That is once start after a few minutes off the circuit connection

  13. Sukdeb saha

    I want to make a circuit which is turn on light after 30 minute of switching

  14. David

    Hi I’m trying to do a timer with alarm every 30 min with buzzer on a 12v battery circuit.can you show me the diagram pls? Really appreciate. Thanks

    • Hello David,
      Thanks for your visit. I am glad that you are interested in this circuit.
      Your idea is great. I’m also wanting to build this circuit. But these days I’m very busy.
      I am sorry. Please wait for me. Soon, I will prepare an article about this circuit for you.


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