I'm trying to make a timer that turns on at a certain time and turns off after 3 seconds, i found a circuit in youtube and made it in proteus, but the output is not the same.

Is there a problem with my schematic?? enter image description here

  • \$\begingroup\$ How does the output differ? Is it a problrm if it is different? What output you were expecting? \$\endgroup\$
    – Justme
    Commented Jan 13 at 6:50
  • \$\begingroup\$ try 44 uf capacitor for C2 \$\endgroup\$
    – Varun
    Commented Jan 13 at 7:10

1 Answer 1


Your time constant is way too long for a 3 second delay. Refer to the NE555 datasheet. The time should be about 1.1 RC, which you have at about 38 seconds, more than 10x too long. So reduce C2 (preferably) and/or R3.

Also, the switch needs to be momentary normally open and released before the end of the time period. If you can't do that, you'll need to add an RC to the trigger input.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.