Les:
1. You're right. Somewhere there was a statement about a ground being available and I magically applied that to the center of the switch. Fortunately, not a big change, and the rest of the circuit and the operating theory are all the same.
2. You're wrong, and I knew this would cause problems. The ground symbol in the schematic is *not* the car frame or battery - terminal or anything in the vehicle. It is the reference potential for the circuit only, on perf board, in a plastic box, isolated from the vehicle ground by the switch and one diode (D1 or D2). While no one is trained this way, there is no functional difference between turning something on and off by switching the DC return as opposed to the DC source - as long as you keep the internal and external grounds galvanically isolated except for the switch connection.
Corrected and final (???) schematic to come.
ak
1. You're right. Somewhere there was a statement about a ground being available and I magically applied that to the center of the switch. Fortunately, not a big change, and the rest of the circuit and the operating theory are all the same.
2. You're wrong, and I knew this would cause problems. The ground symbol in the schematic is *not* the car frame or battery - terminal or anything in the vehicle. It is the reference potential for the circuit only, on perf board, in a plastic box, isolated from the vehicle ground by the switch and one diode (D1 or D2). While no one is trained this way, there is no functional difference between turning something on and off by switching the DC return as opposed to the DC source - as long as you keep the internal and external grounds galvanically isolated except for the switch connection.
Corrected and final (???) schematic to come.
ak