i've been thinking for a while on how to go about making a single button engine start stop system, but a few days ago while taking apart the dash it all fell together when i saw the rod that connects the gear levver to the gearbox!
This basically slides back and forth and rotates to select a gear. It's connected to a mechanical setup in the engine bay that goes to the gearbox.
So for gears: R 1 3 5 it's all the way out and for 2 and 4 it's all the way in, in between is neutral! so having the in between position activate a swith could be the key. If i could either tape a ring around the rod to that would press on a microswitch or tape a magnet to it so it would activate a reed switch i'd be good to go!
when the car is in gear the dash mounted push button would make it start, it it's out of gear it would interrupt the iginition. some sort of creative lighting system would indicate wich function is active.
here's a scematic of a possible system
the only downside is that the gear detector would be activated everytime a gear is selected, so a phisical contact switch might wear out fast, on the other hand a reed switch might not stand up to vibrations so i'm a little unshure about what route to take
now i just have to build it!
