VOXL2 died abruptly and got fixed by itself after a few days.

Jyotish Kumar

Hello,
Our VOXL 2 was connected to our drone. The drone had been functional for long lime and was being used for development on our end. Suddenly, VOXL 2 was not turning on. We observe that connecting the VOXL to power module, the light near the power connector on VOXL just blinks once in red and none of the other lights are on. We also observe slight heat coming from near where the power module connects to the VOXL if we keep it connected for some time (~20 seconds). The temperature is not too hot. The diode near the power module connector seems to be shorted when inspecting with multi-meter.

We have checked with different PowerModuleV3 and have tried changing the wall adapter also.
This happened after the external ESC malfunctioned, overheated and got damaged due to unknown causes. ESC failing has happened to us in the past but it affecting the VOXL is not understood. The power distribution is as shown in the picture, where pass through from the power module is connected to the ESC.

We went ahead with raising an RMA request and while we were in the process of shipping the VOXL to Modal AI for RMA, it started working without any repairs.
We observe normal operating behavior while testing subsequently. So, we are unsure if we should proceed to ship it despite the problem now being resolved.
Requesting you to kindly advice regarding the further steps, considering that the VOXL has to be used in our drone.

Thank you for your inputs.

Adrian Hidalgo

@Jyotish-Kumar that's interesting behavior. While the Voxl2 is working, it's hard to tell if it will last without inspecting it. I would suggest still shipping it back, unless you would like to still work with it as is.

Vinny

Hi @Jyotish-Kumar
It sounds like your power module has (or had) a short on the 5V rail.
I suspect one of three things:

The short was intermittent which helped it eventually go away. Cabling Issue perhaps?
The short was from a small solder whisker which eventually burnt up or got knocked off.
You changed power modules

The behavior you described is exactly what would happen with a "weak" short on a power module. The 5V would appear shorted using a meter when the cable is plugged in, hence you measure it across that protection diode. The RGB LED would very briefly flash from the first voltage rise as RED (since it is out of range) but then promptly go away since the 5V rail is collapsing. Voxl2 would not get warm since it is OFF and the short is external.

Also I see your power module is using an MCBL-00062-1 cable and not an MCBL-00001.
Make sure you use ONLY an MCBL-00001 to power the Voxl2. MCBL-00062 is meant for Flight Core V2.
https://docs.modalai.com/cable-datasheets/#mcbl-00062
https://docs.modalai.com/cable-datasheets/#mcbl-00001

Here is a quick test for you to try:

With no MCBL-00001 or Power Module or anything else plugged into Voxl2, measure that diode again. You should see high resistance (~>100k) using the "Ohm" mode of your DMM, and if you use "Diode Mode", you should see ~0.5V VF in one direction and ~2.5V in the other.
If you see that, make sure you have a new (or unmodified power module) and try to use your system as normal. If all else seems OK, then I suspect all is OK and you did indeed have an issue with your power module

Voxl2 has a built in protection for input shorts, under, or over voltage and output shorts. So, I am not at all worried that this type of failure lead to any damage on Voxl2. It did what is was supposed to and not turn ON.

Going forward make sure you inspect all cabling carefully and use a microscope when soldering to be sure there are no whiskers left behind when done. The Power Module has a lot of "easy to short" access points on it, so soldering on that should be done with caution.

Hope this helps.

Jyotish Kumar

@Vinny
Thank you so much for your highly informative reply. This was very helpful.
I have tried the tests that you suggested, and unfortunately it looks like there is some problem with the protection diode.
The diode is measuring ~0.5Volts in both forward and backward direction and the resistance is measured in the ~1.5Kohm range. So looks like something is still wrong.
I think we will continue with the RMA and request you guys to take a look at the board.
Thanks a lot for your help.

Vinny

Hi @Jyotish-Kumar
The ESC malfunctioning should not impact the 5V output side of the power module.
If you are getting low resistance on that diode, then it was over-voltaged.
That diode is rated for 27V, so the only thing I can think of that would cause that is a short to the VBAT input from the ESC to the 5V rail. Then, if the ESC malfunctioned leading to an energy dump that can create >27V in uncontrolled back EMF.

Was this setup in a crash? Was is powered by a power supply?
Both of those are common reasons for our protection diodes on the Power Module or ESC or Voxl2 to get damaged from extreme over-voltage due to energy dumps.

If you do an RMA, we can certainly test the Voxl2 in an isolated environment to make sure it is still functioning. If we see that diode is damaged, we might be able to repair it at some cost, but it may be that some other system component was your root cause and you can do it again if you do not identify and fix the reason(s).

Thanks!