This setup is really simple and should not require a drawing or specific parts.
I have a standard dual H motor controller that will be powered by its own 12V battery. There will be a toggle switch to turn 12 Volt power on and off to the motor controller. This switch is independent of the PWM and control lines from the Arduino controller.
I want my software to be able to determine if the motor controller is powered or not. In other words, I want to be able to tell if that switch is open or closed. Any ideas? The only thing I have come up with is a double pole-double throw switch. Half wired to 12 Volts and the Motor controller, and the other half with a pull-up resistor wired to a digital IO pin... Any other ideas or did I just answer my own question?
DPDT switch
+12V +5V
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switch \
\
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Motor Ctrlr R1
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common ground