Power supply faulty

tcg6000

Hello there,

My Voxl-Mini ESC just blew up.

Two, actually.

The 12v 3A power adapter that we ordered from ModalAI decided to start outputting 21v.

I didn't notice until I had lost two ESC's.

I was wondering how this could be remedied...

Thank you!

-TJ

tcg6000

The EE coworkers were curious and dug the power brick out of the trash... "Well there's your problem!"

Vinny

Hi @tcg6000
Are you able to provide a little more context here?
Technically speaking, 21V into the Mini ESC will not damage anything. We are rated for 2S-4S as listed here: https://docs.modalai.com/voxl-mini-esc-datasheet/, but 21V is only 3V above that limit and not hear the ABS MAX limits.

We do not advise to use power supplies for our ESCs, and we have that written in many tech docs posts and forum responses, so that is why I am hoping you can tell us more, and include photos of the Mini ESC, and try to help elaborate on what you mean by "blow up", and any other descriptive behavior you have.

Most commonly when a power supply is used for motor spin testing, power modules and/or ESCs do indeed get exposed to very large over-voltage spikes since a battery is able to absorb the back EMF and/or energy dumps, whereas a normal bench power supply cannot sink current, and it creates an inductive spike often times up to double the rated voltage, thus damaging components in the system connected to the power supply.

It may be likely here that 12V 3A supply, if used to spin motors, failed to handle the load and then a very large voltage spike was created by the uncontrolled back EMF pretty much damaging everything connected to the power supply, including the ESCs.

Thanks!

tcg6000

@Vinny

I can gladly provide more context.

I was using the 12v 3A power supply (MPS-00005-1) for powering my VOXL2-Mini through the VOXL2-Mini ESC.
I have been doing this for months now for benchtop development. I don't use it when I am doing any motor tests; I use batteries for that.

Nothing "blew up". I heard a "pop" at one point. Assumingly from the power brick.

What happened: I lost SSH connection to the drone, and looked over to see the LEDs had shut off. I unplugged the power to the drone, then reconnected, to see that that did nothing. No LEDs on the VOXL or ESC (which usually have, quite obvious, LED activity). I had another drone handy, and plugged that into the power supply. It worked for a few minutes, then gave the same issue. No power, no LEDs.

Applied multimeter to power supply and saw 21v. Stopped there.
[edit] I shouldn't actually say I stopped there. I have an an adjustable power supply available, so I tried 12v from that into the ESCs. That did not work. Power supply acts as though the lines are shorted or reversed. It shuts itself off when that happens. [/edit]
Thank you!

-TJ

Vinny

Thanks @tcg6000!!
Very clear and informative response. Thanks for taking the time to explain.
It sure does sound like the wall power supply we sold you faulted and self-damaged itself.
It seems as if the issue may be the TVS diode on the Mini ESC did it's job, and protected against a very large voltage spike from the power supply failure.

It's unfortunate, and may be a hassle for this, but if you can do an RMA for us with both of the M0129 ESCs we can make sure all we need to do is replace the TVS diode(s) for you.
Details on our RMA process are here

I will also make sure we replace your 12V supply free of charge. I'll see if we can get one shipped to you prior to the receipt of your RMA.
I'll talk to the production folks and see if we can get you an additional credit on the TVS diode replacement and RMA charges, assuming that is all we see.

The good thing is, I would suspect your Voxl 2 Mini boards are well protected by the ESCs and I would bet they work without issue. However, if you have some means to test them as well before sending the RMA, you can at least "kill two birds with one stone". If they show any anomalous behavior, then at least you can get them all looked at together.

Hope this helps.

tcg6000

@Vinny

Thank you for the information and the quick responses, I really appreciate it.

Is there any way you can get me the part number for the outlined part?:

Vinny

Hi @tcg6000
We understand your urgency, and an RMA will take some days to complete on our end.
I can provide you with a part number, but you need to be aware of a couple things:

We will not just check and replace (as needed) the TVS diode, we will run a full factory test and check for other issues. Should any arise that seem to be related to the over-voltage, we will fix and credit accordingly. If we could not find the root cause of other potential downstream failures, we will replace the ESC(s)
Please note soldering to replace parts will void any warranties on that board, S/N M2300000M81. And if you decide to do that on the other one, please share that S/N. So, if you do replace those parts yourself, and you find you still have other issues, we cannot honor the warranty and RMA credits I just mentioned above. Basically, replacing parts now makes the whole process "at your own risk".

That part number, should you still wish to replace on your own is (here is a digikey link):
https://www.digikey.com/en/products/detail/littelfuse-inc/SMF4L17CA/10710004
If you review the specs, you'll note it starts to conduct ~19V, hence why @21V if it was sustained, effectively looked like a short circuit to the power supply, and the TVS was exposed to the condition long enough to short it out too... (at least that is my opinion)

I will follow-up internally on that free replacement power supply order today. I'll try to make sure it get's processed today or tomorrow.

Let us know what you decide, and if you do replace it, let us know if that fixed everything for you.

Thanks!
Vinny