Circuit wiring issue

[idi]

Hi all,

I need some help on a little project i am doing. I have attached a diagram of the circuit to give a clearer understanding of what i need.


The circuit at the bottom is for a Nexus tablet. I have extended the power switch so points A and B on the diagram are the switch. e.g. which i touch them together for a quick second, the screen turns on, just like the power button on a phone. I want the screen to turn off and on based on a 12v feed. So when the feed is first turned on, i want the button to be pressed just once (points A and B joined and then 'released'), and when the feed is turned off, i want the button to be pressed just once again.

I obviously can't connect the 12v feed to the circuit since all i need to do is join points A and B.

Is this a simple thing to do? How would i approach it? is there anything i can buy made ready for this?

Thanks

 

[idi]

it can be done with electronics, using a dual 556 timer chip, but the problem is power will be needed to switch the tablet off again, which means using the 12v constantly or a battery....if your ok with soldering and components. i can sketch you a drawing.

Yeah i'm confident with soldering. It would be great if you could draw me a diagram.

Thanks

 

[tazz]

Circuit should work ok.....choose resistors and caps to give required time, so start with 1k resistors (R1 & R2) and 1uF caps (C1 & C2) should give a few seconds. sw+12v is the switch power supply, 9-12v is constant supply battery or psu.
when power turns on relay 1, relay 2 will com on for a few seconds, shorting A & B.......when power is switch off to relay 1, relay 2 will come on again for a few seconds, shorting A & B, circuit shows 2 555 timer ics, a 556 can be used just check pin layout (didnt have 556 in my cad library) post back a tell us all how you got on...
View attachment Dual Time on Delay.pdf