Servo reverse connection protection

Using Arduino Motors, Mechanics, Power and CNC
1

Hi!

I am building a simple servo tester to set RC servos at appropriate angles etc. However the connectors I've got for the servos aren't polar (they look the same from any direction) and I've heard servos easily take damage from reverse current. The servos have the connectors in this order:
[GND][VCC][Signal]

I was thinking of putting a LED on the GND line, so no current can flow into the signal if it was accidently reversed, and I would get a "Connected" light too.
Would this be enough to protect the servo?

2

How would that work? What about the forward voltage of the LED?

It's not an easy thing to do with passive components as its perfectly valid for the
signal line to be at ground, then the connector truly is symmetric. Protecting the
signal line with a series resistor will protect your tester, but not the servo itself
(which may attempt to power itself from its signal line (incorrectly connected direct
to ground).