Is this a protection diode?

[zzyzx]

I reversed my genius cp's battery leads, (careless soldering of battery connectors). I was rewarded with the reek of melting components and the escape of the magic smoke. Got it working again, however I have a question on the theory of operation. There is a schottky diode in series with the circuit ground (this diode saved the board :>), is this diode solely a protection diode for reversed battery leads or is it also protection for the motor switching circuit? Currently have a full size diode in the circuit. Mostly my concern is functions I might not be aware of that it plays in the circuit. It is a schottky right?, didn't check it till after it grenaded.

[Joydeepb]

Yes, the ESC should have at least one flyback diode, most commonly a schottky diode connected across the power lines to suppress reverse transients. If nothing else, the mosfets of the motor driver should have had flyback diodes.

With a burnt flyback protection diode, your receiver will be more susceptible to electrical noise from the motor driver. If your receiver is suddenly unresponsive while the motor is running, now you'll know why.

[zzyzx]

Flyback diode, thanks. Heard the term before, couldn't for the life of me remember it. Got some reading to do, appreciate the help. Engineer by trade?, or just highly motivated amateur like myself?

[Joydeepb]

Both, I guess - I work with robots. Spent a lot of time designing electronics for them, and have had my fair share of "why does the uc reset when the motor is running?"

[Heli-opolis]

Originally Posted by zzyzx

Engineer by trade?, or just highly motivated amateur like myself?

Or, just a strong survival instinct in a hobby that demands one?

[Intheway]

Originally Posted by zzyzx

I reversed my genius cp's battery leads, (careless soldering of battery connectors). I was rewarded with the reek of melting components and the escape of the magic smoke. Got it working again, however I have a question on the theory of operation. There is a schottky diode in series with the circuit ground (this diode saved the board :>), is this diode solely a protection diode for reversed battery leads or is it also protection for the motor switching circuit? Currently have a full size diode in the circuit. Mostly my concern is functions I might not be aware of that it plays in the circuit. It is a schottky right?, didn't check it till after it grenaded.

In addition to the fly-back, shunt, swamping, kickback or whatever you want to call them diodes they have on both motor driver circuits, thankfully they do have a "protection diode" on the input but it isn't actually in series with the ground and or power leads, but is instead across them. Plug the power in correctly and everyone is happy and that diode is reversed biased. You already smelled what happens if you reverse the power in.

As you suggest, this diode can save a receiver from a backwards battery in some cases. Jazzjohn could tell a better story about how well these protection diodes work than I can, but apparently it comes in handy if you make that tragic mistake.

Glad to hear the receiver survived. As long as you don't do that again, you don't really even need that particular diode, but you are smart to have one back in place unless you would rather pay $80 next time!

[Jazzjohn]

Originally Posted by Intheway

. Jazzjohn could tell a better story about how well these protection diodes work than I can, but apparently it comes in handy if you make that tragic mistake.

Thank you for giving credit where credit is due for plugging a battery in backwards. I'll never live that down, right?

[Heli-opolis]

Originally Posted by Jazzjohn

Thank you for giving credit where credit is due for plugging a battery in backwards. I'll never live that down, right?

I've done it more times than you so I deserve some 'credit' too!

Don't mind me, I'll just go lay by my dish now waiting for feeding time.

[zzyzx]

It's hard to admit to for sure but so easy to overlook when you finally get around to wiring up the pile of batteries you've been meaning to get to. Easy to be complacent about a task you view as simple and mundane. I've taken to carrying a small volt checker to use before binding, has the added bonus of double checking polarity. I've also again started checking for a short to ground after a repair before powering up. How long before my caution succumbs to laziness again? History would suggest a few weeks, I'll find it again next time, there will be another.