Many electronics circuits and projects for learning in simple ways.

Timer set for 30 minutes using transistors

This circuit is based on learning of the discharge and charge of the C, which 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.

Timer set for 30 minutes using transistors


This circuit is working as video below:

When you click the switch S1 will cause LED1 light told state ready to run S2 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 flow to the bias for transistor Q1. Q1 and Q2, which work together to Darlington Compound. To have growth rates high to drive the LED2 light over time 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.

Related Links
Electronic switch timer
Led delay timer

5 Minutes Time Delay using CD4093
Switch off delay circuit by 2N4871
10 Second Fan ON delay time by transistor

This Post Has 14 Comments

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

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

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

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

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

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Close Menu