I have a car with courtesy lighting circuit that is always hot. When the doors are opened it grounds the system and the lights come on.
I spliced into the car an electronic rear view mirror with a separate line and a high side trigger to fire the maplights in the courtesy lighting circuit.
Problem was, I needed some sort of circuit to splice into the open ground line of the courtesy circuit just upstream of the door ground switch that will throw 12V+ on the map light circuit when the door switch closes (grounds) the circuit.
Then I got greedy.
As long as i was at it, why not have the timer maintain the original ground to keep the original courtesy lights on briefly after that ground was lost
So I needed either a schematic to sense the courtesy circuit getting grounded and then port 12V+ to the maplight line, or a more elaborate schematic to maintain the ground (timer) and also maintain the high to the maplights for a period of time, say 10 seconds or so after the ground is interrupted.
Thus, trying to simplify.
Module should have it's own separate power and ground.
Module should trigger when when it becomes grounded thru the hot door ground switch.
Module should then;
1. initiate timing
2. trigger a +12 high to the map light line
3. maintain the courtesy circuit ground (thru the separate constant ground) and +12 high after the door switch ground is broken, for a short timed period
4. kill separate ground and +12 high signal and ideally draw no current until grounded thru the door switch again.
Got a schematic from a guy that supposedly does all that.
I haven't cobbled together circuits in a while and never with a 555.
How does it look to you?
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