How to wire in a vehicle "kill" switch....
If you use your kill switch to instead switch the positive of the battery, you could then use the fact that alternator voltage is always going to be higher than the battery voltage, put the car-side of the switch to the positive input of an op amp, the battery side to the negative input of said op amp, and run the output of the op amp to one side of a relay sense coil, and the other side of the coil to ground. The relay will trigger (turn on) when there's a voltage difference between the sides of the switch, and you can use that relay to trigger your ignition and/or fuel cut.
I can also design you another method if you change your kill switch to a SPDT (3 terminal), DPST (4 terminal) or DPDT (6 terminal) one. DPST or DPDT are really ideal, if you could find them.
Also, the 'run from the battery only' idea from your local guy IS still a valid idea. As long as you're not bumping a 2000w system down the track, your battery will barely get drained, and you'll have the advantage of the alternator producing less drag. The higher the current draw from them, the more drag they produce.
I can also design you another method if you change your kill switch to a SPDT (3 terminal), DPST (4 terminal) or DPDT (6 terminal) one. DPST or DPDT are really ideal, if you could find them.
Also, the 'run from the battery only' idea from your local guy IS still a valid idea. As long as you're not bumping a 2000w system down the track, your battery will barely get drained, and you'll have the advantage of the alternator producing less drag. The higher the current draw from them, the more drag they produce.
Thanks for the help...great ideas
