Protection of reverse voltage of an arduino

Have any others used a diode like the MC78M05CDTG to protect an Arduino from reverse voltage?

I am creating a board that has a 12v 5 amp power supply to control various LEDs. I am going to place a voltage regulator (7805) in line to the arduino to bring it down to 5v. I want to protect the Arduino from all the other power connections and in case I'm an idoit.

Am I over thinking this setup?

Have any others used a diode like the MC78M05CDTG

That's not a diode...

You can use a series diode but you'll get a voltage drop (about 0.7V) so the diode should be on the 12V side of the regulator. Or, a Schottky diode will only drop about 0.3V which you might be able to live with on the 5V side of the regulator.

You can use a reverse diode to ground, which will "short out" any negative voltage. In that circuit there should be a fuse so the fuse blows before you fry the diode & power supply.

and in case I'm an idoit.

Use a polarized connector and check everything with a multimeter (or LED voltage tester, etc.) before connecting the 1st time. Or, go-ahead and try a series diode on the 5V side until everything is working OK. It should "work OK" with the slight voltage drop.

I know I can plumb 12v right to the Arduino. But is it horrible to run it that high? I’d like to chill it out a bit before it gets to the arduino.

Use a little switching regulator to make 5V for the Arduino.

https://www.pololu.com/product/2843 or https://www.digikey.com/product-detail/en/murata-power-solutions-inc/OKI-78SR-5-1-5-W36H-C/811-2692-ND/3438675 as examples.