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pulsed output on `permanent` input

Simon_m74

Jul 25, 2016
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I need to turn a TV out of standby automatically upon power up.
There`s an LED that comes up, upon power. When the standby button is pressed, the LED flashes a couple of times (about 0.5second intervals) then when the tv fully turns on - the LED is off.

So I hope to be able to do something like this:
555-oneshot, that pulses a relay to `press` the standby button, once pin 2 is triggered.
but I want it to `ignore` the LED signal (trigger) after initiated, until power loss (or at least until the LED goes off).

I cant think how to get the 555 to ignore a signal permanently - or until the trigger is off after its triggered.

The other thing is that the LED will then produce a high signal when on - so the trigger will be high, where as the 555 likes a low trigger.

Any help please!
 

Simon_m74

Jul 25, 2016
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Ok, I`ve had another look at the `boot up` sequence of the TV.
the standby button does not work for about the 1st 2 seconds of power.
I have seem to hold the standby button while it comes out of standby.

So it now seems I need this:

upon power (LED ON) wait 3 seconds - then trigger the 555, to oneshot pulse for 10 seconds

Advice please.
 

Harald Kapp

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Nov 17, 2011
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I need to turn a TV out of standby automatically upon power up.
My first look would be into the menu whether there's an option for exactly that behaviour.

Doing this in "discrete" 555 logic is certainly possible but probably a bit cumbersome what with all the different timings and so.
Would you dare consider a microcontroller? Sensing power on (either from the LEd or directly from mains), waiting a specified time and issuing a timed pulse for the standby button is easy on that route. An inexpensive arduino nano (less than 3 € from china) is good enough for this.
 

Simon_m74

Jul 25, 2016
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Jul 25, 2016
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I was going to try to use a 555 as I needed to time the system..
But thanks very much for the suggestion of an Ardiuno... I have a couple of Nanos spare.. so I`ll start setting them up (2 TVs to do)
 
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