delayed 555 timer from a high trigger

Thread Starter

simon_m74vr

Joined Sep 12, 2019
2
Hi,
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 ?
 

dl324

Joined Mar 30, 2015
8,761
Welcome to AAC!

From a Signetics Linear Applications Handbook:
upload_2019-9-12_16-52-27.png
You need a base resistor on T1.
 

crutschow

Joined Mar 14, 2008
23,141
What is the supply voltage?
What is the trigger voltage?
Can the supply voltage be used as the trigger voltage?
 
Last edited:

Thread Starter

simon_m74vr

Joined Sep 12, 2019
2
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.
 
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