delayed 555 timer from a high trigger

Thread Starter


Joined Sep 12, 2019
I need to a circuit to do the following:

When input is high (power on) wait 3 seconds, then pulse an output to a relay for 5 seconds.

Its to take a TV out of standby automatically.
When its powered on, a standby LED is on.
When the standby button is pressed, the LED flashes a few times then the TV kicks into life.

The standby button does not work for the first couple of seconds - hence the 3 second delay
The trigger is going to be high - as fed from an LED
ouput to drive a relay to `press` the standby button for the duration of the LED flashing - that should be ignored by the input.

Can anyone help please ?


Joined Mar 14, 2008
What is the supply voltage?
What is the trigger voltage?
Can the supply voltage be used as the trigger voltage?
Last edited:

Thread Starter


Joined Sep 12, 2019
Thanks all.
I`m changing my plan... I`m going to use an arduino.

The trigger will be from the LED as soon as I turn on the mains to the TV.
Then I`ll program it to wait, then output to a relay for `x` seconds.

Thanks tho for the 555 help - although I`ll be not using it.