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I have created an arduino shield and i want to measure the voltage between the GND pin and 5V pins, to see if i see a voltage difference between the two points, in order to test if my pcb is fine.

My concern is since these are right next to each other and my multimeter probes are thick.

If the multimeter probe that 5V pin touches the GND pin, in other words, if i short circuit the 5V and GND pins, then will my arduino be safe?

I am afraid of damaging the arduino.

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  • When I want to be sloppy with taking a ground point on Arduino I typically use the USB shield; it's hard to miss. Is this all there is to the question or am I missing something? – timemage Feb 2 at 21:28
  • My question is: If i short circuit the 5V pin, with the GND pin, will this damage my arduino? – user1584421 Feb 2 at 21:29
  • @timemage The shield of the USB socket shouldn't be connected directly to ground. The Arduino breaks the specs by doing that. Instead it should be connected to ground via a large (1MΩ) resistor. This is so that when the plug is inserted the shield connects first and a current-limited path between the grounds is created first to balance the two ground levels. Only once that is done should the main power and ground be connected. So relying on the shield of a USB socket is not always a good idea... – Majenko Feb 2 at 21:33
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    how does testing the power supply voltage test the board? ... you would get 5 V without any board – jsotola Feb 2 at 21:35
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    @timemage No, not a conversation. Just a moan about Arduino's shoddy design practices... – Majenko Feb 2 at 21:39
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It all depends on how you are powering the board.

If you're running it from USB then the computer should shut off the power to the USB port. If it doesn't then the Arduino has a small self-resetting fuse on the USB power which should shut the power off for you.

However if you're powering through the barrel jack there's no protection. Worst case scenario: it will blow the voltage regulator, which then "fails short", meaning it passes the whole of the input voltage through to the microcontroller, which then kills it.

So yes, it's possible to damage the Arduino with a short circuit.

Most multimeters have a better way of testing the board though: either the "beepy" continuity test, or the resistance mode. You can use that to test the continuity or resistance between your 5V and GND pins without having to connect the shield to the Arduino at all. 100% safe.

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  • I am powering the board therough the computer's USB. However, you seem to have misunderstood. I did not explain this correctly. I don't want to test continuity. I want to measure between the GND pin and the 5V pin, to see if my voltage is indeed 5V (i was worried my shield pins do not touch the board). – user1584421 Feb 2 at 21:44
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    Then again you can do that without power - test the continuity of the pins from the shield to the board. – Majenko Feb 2 at 22:01
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No, shorting +5 to Gnd is not safe, although a brief short might not cause damage. If it persists, you could burn a trace, overheat the voltage regulator, or damage the computer USB if that is what powers your Arduino. Most computers will sense that short and disconnect power to that USB until the short goes away, but you don't want to count on it!

If your meter has probes with clip-ends, use those to clip two bread-board wires, and probe the Arduino pins by plugging the wires into your shield. If the shield has no pin sockets installed, at least the bread-board wires are small enough not to short adjacent pins.

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  • I hope i did not damage the arduino then. If i did damage it, then the arduino would not work at all? Because i did make a connection. How would i know if everything is ok? – user1584421 Feb 2 at 21:45
  • If it was a brief contact, the board may well have survived. The most basic test is to load and run the blink.ino example. One that I use regularly is to write one that blinks each pin in sequence, then probe each pin with an LED and resistor to check that it works. – JRobert Feb 3 at 1:45
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mostly yes , mostly no . my old arduino got a little too much dusty and when i cleaned it with mild amount of water (nervously) and dried it partially . nothing happened to it . it was operating normally . but some beginner manuals tell not to short circuit it . dunno what's going on ...

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  • I'm thinking you mean "partly" rather than "mostly". For what it's worth, pure water doesn't conduct all that well at all. So if you haven't gotten sufficient salt, finger oils, soaps, or any other impurities, it may operate completely submersed. I am not recommending that you try it. – timemage Mar 7 at 15:12
  • oh , yes . that is why it didn't explode ... – Raj Mar 9 at 14:09

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