For example: my laptop, while connected to the Arduino over USB, runs just fine, while the Arduino locks up.

  • 1
    \$\begingroup\$ Please post a schematic and image of how the DC motor is connected. The circuit probably needs bypass capacitors and better grounding and power supply connections. \$\endgroup\$
    – PStechPaul
    Feb 9 at 2:03
  • \$\begingroup\$ @PStechPaul I'm not exactly looking for a solution but rather am trying to find out why consumer devices don't seem to be affected. \$\endgroup\$
    – kraber94
    Feb 9 at 2:10
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    \$\begingroup\$ What is the relation of the DC motor and the other components (PC, Arduino, consumer electronics)? This question can't be answered without knowing their relation to each other. \$\endgroup\$
    – Velvel
    Feb 9 at 7:07
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    \$\begingroup\$ Also, apart from Arduino being a student board not suitable for pretty much any purpose (including learning), AVR always had a nasty reputation of performing poorly when exposed to EMI. Just don't use such legacy MCUs from the early 1990s and you should be good. \$\endgroup\$
    – Lundin
    Feb 9 at 10:51

1 Answer 1


Because Arduino boards in general - and I guess your circuit in particular - do not have the required protection devices included. A laptop or a desktop PC does have protection on its ports to fulfill standards and other requirements.

If you, on the other hand, exceed the specification of these protection devices, a consumer grade device will have failure modes as well.

But also, the USB-cable will play its role. It presents an inductance to the EMF on its way from the Arduino to the PC. This inductance will limit the effects of the EMF.

For example:

A standard free-air phone-line will have lightning arrestors to protect the devices connected. The devices may be damaged during a lightning strike, but it will not pose any danger to humans (I am assuming for the sake of the example). On the other hand, a EMP blast will destroy it in a rather more violent way.

Another example:

An industrial motor-drive controller will not have any issues with driving an motor or sustaining any back-EMF. Your Arduino does.

  • \$\begingroup\$ The exact answer I was looking for. Thanks! \$\endgroup\$
    – kraber94
    Feb 9 at 2:34
  • \$\begingroup\$ Except Arduino actually claims to be compliant with CE and FCC requirements. docs.arduino.cc/certifications where commercial requirements (like those of a laptop) are the lowest. If they have claimed to just be a prototype board unsuitable for all the things that various strange people around the world insist on using them for, then they wouldn't need to conform to EMC directives. But they actually made that claim, so this answer is incorrect. The correct answer is: because it's a bad product which doesn't conform to to its own listed EMC requirements. \$\endgroup\$
    – Lundin
    Feb 9 at 10:57
  • \$\begingroup\$ @Lundin But do you have measurements or citations to support your claim? And in what configurations? A board alone, with no connections besides USB or power, is likely much more resilient than whatever several things OP has connected to it. They can't possibly test every configuration and shield, only the main board (granted, if at all). \$\endgroup\$ Feb 9 at 12:39
  • \$\begingroup\$ @TimWilliams I have no desire to dig through their test reports if at all made public. The link I posted does list CE declarations and so on for every single product. Reasonably they would have been tested in the way most people are expected to use them, like together with a certain 230VAC adapter or with certain batteries and so on. Obviously any manufacturer can lie themselves blue towards the test house, such as for example testing Arduino with no firmware loading and no peripherals being used. \$\endgroup\$
    – Lundin
    Feb 9 at 13:44
  • \$\begingroup\$ @Lundin Indeed, therein lies the catch -- the board itself might work, for some typical configuration [of hardware and software], but it's utterly impossible to predict what an end user might do with it; this is why EMC must be tested for every finished product, more or less regardless of what components they are made from. Or in a related matter, why FCC frowns on custom firmware for radio peripherals, routers, etc. So much EMI is software-dependent these days. \$\endgroup\$ Feb 9 at 14:38

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