I am using an Arduino (Elegoo) Mega with Motor shield to drive a digital train set. The Motor shield is powered from a 12v 1.1 amp dc power supply and I have the Arduino plugged into my laptop via USB. I have an app which sends commands via serial to the mega which are then turned into commands for the train set and sent down the line.

When using this all of a sudden the main chip on my Arduino blew up and my Laptop seemed to blow a re-settable fuse shutting off instantly (It was dead for about 10-20 minutes then worked again).

Would this be because something caused power to get back through the Arduino to my laptop?

The railway will short from time to time if a locomotive derails for example.

I know there is a trace on the Motor Shield which prevents the shield powering the Arduino. I have now cut this although it says you only need to cut it if using over 12v.

  • Is it a genuine Arduino or a cheap Chinese clone?
    – Majenko
    Jul 29, 2019 at 13:01
  • Its an Elegoo but I have used them for years without issue. To be fair this is the first time I have powered them from a motor shield though.
    – kenjara
    Jul 29, 2019 at 13:03
  • @Majenko This is part of an open source project to make getting into digital train sets as cheap as possible so we are trying to keep costs down hence the clone. If it does turn out that the official board would be a better choice though it would be good to know.
    – kenjara
    Jul 29, 2019 at 13:24
  • It could be that the voltage regulator on the clone is inferior and died allowing 12V through to the rest of the Arduino and hence your computer.
    – Majenko
    Jul 29, 2019 at 13:30

2 Answers 2


Looking at pictures of the Elegoo Mega 2560 they use a "hash fill" for the pour on the tab of the regulator, not a solid fill, and zero vias to another dissipation layer on the reverse. While this may look more funky it provides only a fraction of the heat dissipation of a solid double-layer fill, meaning the regulator is more likely to overheat. Also because this is a Chinese clone the component quality will be lower (cheaper) meaning the regulator probably doesn't have proper thermal overload protection.

So it gets too hot too easily, and pop your Arduino is dead as the regulator fails "short" and 12V gets pumped directly into the rest of your Arduino.

Byebye Arduino, and byebye computer (fortunately temporarily in the case of your computer).

  • Do you agree that by cutting the Vin trace on the motor shield there will no longer be a risk to my computer?
    – kenjara
    Jul 31, 2019 at 13:26
  • Sounds likely, yes.
    – Majenko
    Jul 31, 2019 at 13:26

Be careful dissing Chinese components as 'poor quality' Your TV, Phone, computer and practically any other electronic item you own has chines built components in it. Most of these items are assembled in China anyway. I agree the board design may be poor but component quality from China is fast becoming a thing of the past.

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