When examining the EAGLE file for the Arduino Mega that I downloaded from their official website, I noticed that the ground (GND) is not connected to anything other than the C4 component, which means electrons flows from +5V through the C4 component into the GND.

When I look at the actual board, I see that the GND is indeed only connected to the C4 component and has no path connected to anything else at all.

Does that mean when I plug in the Arduino board to a power source, the electrons from +5V just start piling up at where GND is, since there is not an outlet for it? Won't there come a point where there are so many electrons piling up at GND that electrons at GND start repelling the electrons flowing from +5V, and the circuit just stops working?

enter image description here

  • \$\begingroup\$ as shown here this circuit would ineed not work. I don't have the files myself, but I assume that either this ground connection goes to an internal ground plane not shown, or this is an error. \$\endgroup\$
    – Joren Vaes
    Commented Mar 19, 2018 at 7:57
  • 3
    \$\begingroup\$ May the electrons go to electron heaven or it doesn't exist because there are more than 2 layers and there are some misunderstandings. \$\endgroup\$ Commented Mar 19, 2018 at 8:07
  • \$\begingroup\$ 10/10 it's missing a GND copper pour \$\endgroup\$
    – MrGerber
    Commented Mar 19, 2018 at 8:15
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    \$\begingroup\$ Did you run the ratsnest command to render the pours? \$\endgroup\$
    – Wesley Lee
    Commented Mar 19, 2018 at 8:43
  • 1
    \$\begingroup\$ Just for correctness' sake: Physically the electrons go from the ground plane to +5V (not vice versa). \$\endgroup\$ Commented Mar 19, 2018 at 9:54

2 Answers 2


I downloaded the board files, opened in eagle, and ran the command "ratsnest" to repour all copper pours. Lo and behold, it's as suggested by both me and @WesleyLee in the comments - there is a copper ground pour on the board.

enter image description here

  • \$\begingroup\$ nice one, and shows how this layout is still ever so slightly messed up: The GND connection breaks the shape of the thermal relief. Probably really not an issue at the ripple currents heating up C4, bet then again, it is the capacitor closest to the power pins, so if for any capacitor, thermals matter here. \$\endgroup\$ Commented Mar 19, 2018 at 9:45
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    \$\begingroup\$ Nope. Thermals matter here only when soldering the GND pin itself. And the slightly bigger GND trace will not affect that very much. \$\endgroup\$
    – Turbo J
    Commented Mar 19, 2018 at 13:51

Assuming there is no connection, you would have an open chain. This means no current will flow and no voltage will be built up over the component.

Remember: \$ V = \int\frac{I}{C}dt \$

But the current will be zero.

  • \$\begingroup\$ Note: as mentioned in the comments by Joren Vaes, I expect there's a connection to to an internal layer. This answer assumes someone messed up and forgot to put that connection. I don't have the mentioned EAGLE files here, though. \$\endgroup\$
    – DonFusili
    Commented Mar 19, 2018 at 8:10

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