My goal: to convert a ground signal pulse into a +5v signal pulse.
My question: How on earth do I do this?
Backstory: My Jeep ZJ factory doorlocks operate using 5v logic. My aftermarket alarm uses a pulsed (momentary) ground signal for both the lock and unlock feature (2 separate wires). I'm attempting to use those ground pulses to mimic the function of the native door lock/unlock switch inside the vehicle. The native circuit board inside the doorlock module uses a switched ground to "unlock" and a +5v is used to "lock" the doors. I am attempting to get the aftermarket (2 switched ground wires) to communicate with the native circuit board (1 switched ground & one switched +5v).
The amperage is tiny because these signals drive relays on the circuit board.
Initially I was going to use a 7805 to switch/reduce a constant +12v signal to +5v. I thought that I could use the momentary ground signal on the base of the 7805 so that it would only "turn on" and supply +5v when the ground/base was momentarily pulsed...which worked...but the problem is that when the system is idle (when +12v is on the input and the base is not grounded) there is +12v on the output terminal of the 7805. Therefor this will not work because the output terminal MUST be at 0v when at rest...otherwise it would always be sending a lock signal.
Is there a logic level relay that completes a circuit ONLY when a ground is supplied to it? If so, then I can use the +5v on the circuit board as a source and not have to reduce from 12v to 5v.
With an electro-mechanical relay this would be simple but these component level transistors are a little more difficult to grasp for me.
UPDATE: I just wanted to say "Wow"! I asked a question and within 15 minutes, 4 people jumped in and helped. Thank you, everyone! This place is great!