reverse-voltage protection

[EricVanWyk]

Originally Posted by kamocat

I was thinking about how to implement reverse-voltage protection on a Jaguar or Victor, and I realized that all the polarity sensitive components, with the exception of the electrolytic capacitor, are powered by the 5v or 3.3v regulators.

Reverse voltage protection is very simple conceptually, but gets very expensive when you have high operational power. There are two main types: shunt and series.
A shunt needs to be able to safely shunt many times the operational power for long enough for the breakers to blow. Usually this is a diode or a diode-like device.
A series method needs to be able to conduct the operational power continuously. For an example of a series method, take a look at the schematics for the DSC or Solenoid Breakout.

Originally Posted by kamocat

Couldn't we just put a diode on the supply side of both of those, and thus prevent the motor controller from turning on when voltage is reversed?
(The capacitor, though it would blow hot oil all over everything, can be replaced)

Still need to protect the bridge, per your next statement...

Originally Posted by kamocat

On a similar note, how is providing power to the wrong side different than normal operation? It's still the same to the h-bridge. Why does the motor controller even turn on, if the motor is stopped? The source and drain on a MOSFET can be flipped without issues, correct?

All MOSFETs (that have 3 terminals) have an internal body diode between source and drain. Reversing polarity allows current to flow through the diode and pop the FET.