I'm building a car DVR using a GoPro. The GoPro can be turned on by shorting out two pins on the gopro bus and then turned off by shorting out the same two pins.
So when the car's ignition is turned on I need a 3 second pulse (555 timer probably) then when the cars ignition goes off I need another pulse - this is where I am struggling to come up with a solution. I need some type of edge triggering right? going from 0-12v fires off one pulse / triggers the 555 then dropping from 12 to 0v fires off another timer.
Any suggestions, I think I just need to set up two 555 to be positive edge and negative edge trigged right - how do I do that? Been a while since I dabbled in electronic so I'm a little rusty :)