Hello.
I am a newbie in automobile engineering and in arduino. I want to make a system so that the engine is not allowed to start when the door is open. I have made all the necessary code to get the input but I don't know where to apply the output. I have some relays. But I do not know where to place it in the car ignition system.
If anyone knows where to put it,pls send any diagrams or images.
help will be appreciated.
thanks
Given that when you open a car's door, there's a switch to turn on the overhead dome light and such - I am not even sure why you think you need an arduino in the loop at all. Seriously, if you want reliability, the fewer parts, the better.
That said - regardless of how you control it - you basically want to put a relay switch contacts inline with either the wire that goes to the starter relay (contactor - basically the huge relay that connects to the starter motor) from the smaller 12 volt relay that controls it, or between that relay and the wire that controls -it- (usually from the key switch, but on today's cars it could be coming from the ECU - aka, the "engine computer").
You might also put it on the key switch wiring, too.
Which leads to the issue that if you don't do this right - you can either damage your ECU or another computer in the system (aka - $$$$), or the ECU will refuse to work because you've changed the system, and it has detected it.
As far as diagrams or images - while a general diagram could be drawn - if you don't understand what I have written, then this isn't the project for you. That said, each make and model vehicle is different, and knowing where to hook into the wiring harness to control what you want will depend on the wiring for that vehicle. So go out and purchase a Haynes and Chilton (buy both - you'll want and need it) and study the wiring diagram.
Oh - also - if your car is fairly new, and is using something like a CAN-BUS or other bus-based system - good luck; in those cases (and perhaps even for other cars), your best bet would be to insert your "man-in-the-middle" control at the relay that controls the starter relay/contactor - or afterward between it and the contactor.
Whatever you do - don't try to put a second contactor inline with the first - while it might work - it also might be a recipe for catching fire, unless you make sure to keep your conductors short and cleanly arranged (which in the cramped spaces of most of today's vehicles, might be next to impossible to fit such a device).
You probably don't want to have it cut the ignition while the vehicle is in motion.