I am building a Pi into some equipment just to drive a display. Now this is normally powered by a USB lead with the usual 5VDC. So I will have to cut the USB cable and put ferrules on the leads (omitting the data lines) to connect to the 5VDC supply on the DIN rail.
The question being, if someone gets the polarity wrong in production, will it destroy the Pi, or is there internal protection? Is there typically internal polarity protection on other devices that take power from USB eg phones? Is putting in such protection feasible given (say) the voltage drop produced by a simple diode? What other protection circuits exist that do not drop voltage (if this is even possible)?