Using constant voltage to power mini pc

Thread Starter

josh-j

Joined Sep 12, 2019
4
Hey guys,

I'm currently installing a mini pc into a car. My problem is that I do not want to have to press the power button to turn it in and out of sleep mode. From what I can gather a 555 controlling a transistor or replace the power button seems to be the go. when the ignition is turned on I want to use a constant 12v to send a .5 second pulse to simulate a press of the power button on the pc, and when to voltage returns to 0v send another pulse to simulate the press again. I am able to have constant 12v power supply regardless of ignition position. I am starting this thread because I am brand new to 555s and need all the help I can get. mono/bistable? what pins do what and am i on the right track? also setting up the circuit. any help is much appreciated.
 

crutschow

Joined Mar 14, 2008
23,480
when to voltage returns to 0v send another pulse to simulate the press again.
Why do you need that pulse?
Do you leave the power on to the PC all the time?
If so, how will it differentiate between a power-on and and a power-off pulse so that the pulses are in sync with the power?

Does the power button operate from 12Vdc or from the mini PC internal power?
What exactly does the button do?
 

Thread Starter

josh-j

Joined Sep 12, 2019
4
Why do you need that pulse?
Do you leave the power on to the PC all the time?
If so, how will it differentiate between a power-on and and a power-off pulse so that the pulses are in sync with the power?

Does the power button operate from 12Vdc or from the mini PC internal power?
What exactly does the button do?

The pulse is needed to replace a momentary switch, the power button on the pc. It will have constant 12v to the pc power input and the switch will toggle it in and out of sleep. The pulse won’t go to the pc directly, it will control a transistor that will close a circuit between two pins of the original switch. Ignition on, 12v supply to 555 = single pulse, ignition off, 0v supply, single pulse.

The other part is where I need help. I don’t know how to differentiate the two. If having a pulse at 0 is to hard/ not possible I could also use a changeover rely to send 12v to two different pins. But I’m not sure how to do all that as I’ve never used a 555 before, might not be what I need I’m just basing that off what I can gather.

Thanks
 

crutschow

Joined Mar 14, 2008
23,480
My point is, since the same pulse both wakens the pc and puts it to sleep, how will you synchronize that with the power on and off?
If it's out-of-sync, the power-down pulse could waken the pc, and the power-up pulse could put it to sleep.
 

Thread Starter

josh-j

Joined Sep 12, 2019
4
My point is, since the same pulse both wakens the pc and puts it to sleep, how will you synchronize that with the power on and off?
If it's out-of-sync, the power-down pulse could waken the pc, and the power-up pulse could put it to sleep.
Oh ok sorry I’m with you now. I would want to to start every time so hopefully it will stay in sync. I could just have the pulse on a toggle switch for when I don’t want it. And maybe another switch to turn the pc on/off if it does fall out of sync
 

Thread Starter

josh-j

Joined Sep 12, 2019
4
Do you know for sure whether the power button provides a 12V pulse to the PC, or pulls an input of the PC down to ground (0V)?
No idea what it does, just know it’s a two pin switch. I will have to find out what one it is just yet to test it.
 
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