Thread: Circuit help: Short ground pulse -> long +12V pulse

My car came with the common remote unlock system where one button press unlocks the driver's door, and the second unlocks the rest. I modified this so that all the doors unlock from the first button press, and now I have a spare wire that pulses a GND when I press my unlock button a second time.

I would like to come up with a circuit that will take this GND pulse, and give me a ~5sec positive 12V pulse I can diode into my M2-ATX's ACC sense line. I've noticed that when I start the car or apply 12V to the ACC sense, it takes almost 5sec for the pc to start booting. At this point, I can drop the 12V so that the timer will shut it down again if I don't get in the car for some reason or I hit it accidentally, I don't drain the battery.

I was thinking of some type of 555 ciruit, but have never used these before. I found this schematic for a 555 monostable mode, seemingly for a negative pulse (I assume that means GND):


(From: http://www.uoguelph.ca/~antoon/gadgets/555/555.html)

Supposedly, here, T = 1.1 x R x C. Does the 555 support wide voltage input? Do I need any specific type of resistor and cap, or can I just use a standard 1/4W resistor and electrolytic cap?

Offhand, I remember the other night noticing a 330uF eletrolytic in my parts bin - probably around 25V-50V rating. Could I just take that 555 circuit, toss in that and a pair of 10K 1/4W resistors in series for R (or dig for a 20K or close thereto), and get T = 1.1 x 20K x 330uF = 7.26sec? Is it that simple?

Edit: Just found this schematic (left most), and it answers the input question. Does this look like a better option? Could I just connect where they show the switch to ground to my switched ground pulse?