Turn on screen when given power

[BtheDestroyer]

I'm using this screen and have a question

When you plug it in,it starts in a standby mode where you then have to push the power button to turn it on. Is there any way to force it to start on so you don't have to push the button? or to have the button automatically give a signal once it's turned on?

 

[supersonic_32]

Remove the power button and solder pins together the right way like you would do on a n64 for exemple?

 

[BtheDestroyer]

Would that work for a push-button though? I know it would for a toggle switch.

 

[supersonic_32]

Pretty sure it would, the button is just making contact between two pins, like a controller button is doing contact between his own line and ground. But just to be sure that it will work with your screen, try powering it on and hold the button, if holding it is not changing anything and the screen stays on, it will work for sure, if the screens power on/off continously, it will not.

 

[DuHasst0]

It won't I've tried, has to be a momentary push.

 

[grossaffe]

Pretty sure it would, the button is just making contact between two pins, like a controller button is doing contact between his own line and ground. But just to be sure that it will work with your screen, try powering it on and hold the button, if holding it is not changing anything and the screen stays on, it will work for sure, if the screens power on/off continously, it will not.

a button of this nature is only meant for momentary contact rather than constant contact. Also worth noting that it's also likely meant to work with TTL level voltages and the supply voltage may be higher.

If you just want a voltage pulse as power is applied, then theoretically a capacitor would do the trick. Capacitors are often used for coupling; filtering out any DC component and only allowing an AC component through. In a DC circuit, the capacitor will charge up to the the same voltage as what it's being supplied, at which point there will be no difference in voltage, thus no current. With no current, it is essentially an open circuit. But any time the supply voltage changes, suddenly there's a difference in voltage between the supply and the capacitor so current will again flow until the capacitor matches the supply voltage. In this case, at t=0-, the supply voltage will be 0V for a long time so the capacitor reaches it's steady state 0V. at t=0+ (when the power switch is flipped), the supply voltage jumps to Vs, and the voltage on the capacitor will "slowly" climb to that voltage, and current will pass through. As the Capacitor approaches Vs, the current will eventually drop back down to 0. When the switch is turned off, the capacitor will then slowly discharge to zero (depending on how the circuit is set up).

The problem with this, though, is that the screen likely will not be ready for a button input the instant it is supplied power, so this instantaneous pulse would probably be in vain.

 

[laingsoft]

Couldn't he solve that problem by building the circuit you described, but with a large cap?


OP could also use a small AVR (AT-TINY8) or something along those lines. Might be overkill though.

 

[Bush]

Could you use a relay in it's place to "push" the button?

 

[grossaffe]

Couldn't he solve that problem by building the circuit you described, but with a large cap?
I wouldn't count on it. We don't even know how much of a delay is needed and just how slowly would the capacitor need to charge in order for it to not read a pulse until after that time has passed, etc.. There would have to be better ways of acheiving the desired result.

 

[BtheDestroyer]

Amazingly enough, holding down the button when it's plugged in worked
It took a few seconds to actually turn on, but it does indeed turn on automatically. Thanks for the suggestions guys