USB under voltage detected

I get an USB under-voltage detected, main power switched off error sometimes as soon as I launch the software, sometimes quite a while later after I have applied power to my device. What is this telling me about my setup?

Hi and welcome to the forum,

This means that the voltage level at the USB port of your Otii Arc is low and there are some possible reasons for this.

  1. Your USB port on your computer doesn’t keep the power according to the USB specification. So the voltage is lower that expected.
    If this is the case then try to use a powered USB hub inbetwen your computer and Otii Arc.
  2. Your USB cable is a bad USB cable.
    Are you using the USB cable supplied when you bought your Otii Arc?
    This cable is build specifically for low resistance so use this if possible.

You can monitor the USB voltage by, in Otii application when you have created a project, click Device -> Meters and check the VBUS figure.

Best regards,

Thank you for your quick response on this topic. In response to your comments, we are using a powered USB hub. It is a Sabrent HB-U14P hub. And we are using the supplied USB cable that came with the OTII. Would an external ac adapter for the OTII prevent this issue?

Thank you for your help



Sorry, but that is not a hub you want to use in this case.
Maximum output current per port is 300mA and Otii Arc will consume some of that power.
I would switch to another powered USB hub.
Connecting an external DC adapter to Otii Arc will only slightly reduce the problem.

Best regards,

Thanks for the info. Do you have a recommendation for a powered USB hub that would work better or that you have had good luck with?


I am using two TP-Link UH720 in my setup with 12 Otii Arcs with good results.
Check my setup in the article here: