I recently ran way to much voltage through my Arduino and back into my computer via the USB connection. I'm looking for a USB hub with a fuse or some sort of protection to protect my laptop from these types of mistakes. Any suggestions as to products that would serve this function or other precautions I might take?

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    If you used the barrel jack, the voltage wouldn't have reached the usb connector. So unless you connected the higher voltage to the 5V pin directly there isn't a problem.
    – Gerben
    Commented Mar 23, 2016 at 16:36
  • Thanks for the advice all. In case you are wondering this is what I did electronics.stackexchange.com/q/223983/104362. The board that I was attempting to probe was powered externally at 16vdc regulated to 12vdc.
    – StevieD
    Commented Mar 23, 2016 at 16:54

4 Answers 4


Both the arduino and a USB port do have some protection against wrong connections and such. The arduino has a diode to prevent wrong polarity to reach your power supply, it also have a resetable fuse (the kinda big, often green SMD part close by your USB connection on your Arduino) that should protect your USB port pretty good from its side of the cable. Your USB port also have some good protections going on as far as i know, so basically it should be hard to break a USB port by accident.

That was the theoretical part, In real life things aren't always what they claim to be, so I use a cheap powered USB hub, that i always use as a first line of defense.

  • Not all Arduino have such protections: the Uno does, but a Nano is also part of the family.
    – CQuinson
    Commented Mar 23, 2016 at 8:50
  • The Nano is missing the polyfuse, but does have a diode to protect the USB
    – Hans Neve
    Commented Mar 23, 2016 at 9:13
  • What happens on a UNO vs a Nano when you short +5v and GND? A completely different thing, and that is my point. Anyway, +1 to cheap powered USB hub when unsure of schematic.
    – CQuinson
    Commented Mar 23, 2016 at 10:40
  • Anyone knows about nodeMCU? (Do they have some protection against wrong connections?)
    – JinSnow
    Commented Dec 3, 2018 at 8:19

There are a number of USB Isolator products available all around the world.

Here is a list of just a few:


You get used to what not to do fairly quickly :)

Perhaps what you're after is a ruggeduino - http://www.rugged-circuits.com/ruggeduino/

I get the feeling that this sort of thing encourages bad habits, but then it also encourages more exploration.

You need to think carefully about what you're doing, if you put in any second source of power (e.g. USB + power plug, or USB + a signal from another device).


Please note, that I have no experience in this field, this is simply what I found after some digging.

I was concerned about connecting a Raspbery Pi Pico device to my brand new computer and did some digging in the "USB Power Delivery" specification: Output Over Current Protection

Sources operating in SPR mode Shall implement over current protection to prevent damage from output current that exceeds the current handling capability of the Source. [...]

"Shall" means, that this is a mandatory requirement: Shall/Normative

Shall and Normative are equivalent keywords indicating a mandatory requirement. Designers are mandated to implement all such requirements to ensure interoperability with other compliant Devices.

At this point I am already confident enough to plug the device into my computer, so I'll stop digging into the details here.

My understanding is, that the USB controller will detect the fault, disconnect the device and then upon reset and/or reboot it would start working again.

External protection circuits should not be required, at least that is my takeaway. Maybe for really old computers?


It doesn't seem quite that simple after all, over-voltage protection may not be covered: Over-Voltage Protection Event

The Over-Voltage Protection Event bit May be set when the Source detects its output Voltage exceeds its limits triggering its protection circuitry.

It seems advisable to use some sort of external device after all. Not sure how realistic this failure case is for devices which are powered from the host, but for devices with external power this seems smart.

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    This answer is about overcurrent protection. The question was about overvoltage protection. Not quite the same! Commented Aug 29, 2021 at 12:57
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    @EdgarBonet Thanks for pointing this out, it seems, over-voltage protection is not always present, so this is an important correction.
    – asynts
    Commented Aug 29, 2021 at 14:16

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