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 ?

 

The standby button does not work for the first couple of seconds

First couple of seconds from what?
Are you turning the main's power on and off to the set?

 

Welcome to AAC!

From a Signetics Linear Applications Handbook:

You need a base resistor on T1.

 

What is the supply voltage?
What is the trigger voltage?
Can the supply voltage be used as the trigger voltage?

 

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.

 

Take a look at these posts -

https://forum.allaboutcircuits.com/threads/pulse-sequence-generation.161138/#post-1408557 Post #1

https://forum.allaboutcircuits.com/...ger-another-at-intervals.163070/#post-1431617 Post #10

https://forum.allaboutcircuits.com/...ess-on-off-dual-function.130963/#post-1427020 Post #9 on



Regards, Dana.

 

Take a look at these posts -

Hooray, you found someone who wants to generate a pulse using a microprocessor instead of a 555.

 

Hooray, you found someone who wants to generate a pulse using a microprocessor instead of a 555.

Enjoy your day.