Is there a way for me to have this work the opposite way?

I have one cable with an alligator clip hooked up to the reset pin and another hooked up to ground.

When I clip them both together, the board resets.

However, I would like for this to work in the opposite way such that they’re already clipped together and when you detach the cables, the board resets.


My personal preference would be to attach a NOT gate to the RESET pin. This can be constructed very simply from a single NPN transistor (or N-channel MOSFET) and a resistor.


simulate this circuit – Schematic created using CircuitLab

With the wire disconnected R1 turns on Q1 which pulls the RESET pin LOW. With the wire connected Q1 is turned off, allowing RESET to be pulled back up by the pullup resistor that's built into the Arduino.

This method also won't interfere with the programming reset action of the Arduino.

  • Thanks for sharing this. I will give this a go and update how I get on
    – Yemi Davis
    May 22 at 16:41

The easiest way to do that would be to use an external pulldown resistor (a resistor from the reset pin to ground) and connect to Vcc (5V on the Nano) via your alligator cables.

As long as the alligator cables are connected, the reset pin is held HIGH through them. When you disconnect them, the pulldown resistor pulls the reset pin to LOW. That holds the Nano in reset until you again connect the alligator clips.

If you want the Nano to reset and then directly work again without the alligator clips reconnected, it gets more difficult. One way I can think of is building a monostable vibrator circuit, which gets in the excited state, when your alligator clips are disconnected, resets the Arduino and then goes back into the stable stable, letting the Arduino execute its code. Though that is more an electrical question, than an Arduino one.

  • 1
    Since there is already a 10K pullup resistor on the reset pin you will want the pulldown to be considerably smaller than that. Probably in the order of 100Ω. That will cause considerable power wastage...
    – Majenko
    May 21 at 23:35
  • Thanks so much for sharing this! I’ve Bus true this out, hope we, it doesn’t seem to want to work. I have both cables with the alligator clips hooked up to 5V (am I right to do this or does the second clip need to go elsewhere?) It’s worth mentioning in doing this on a veroboard and haven’t yet snipped the kegs off the resistor. Interestingly enough, when the leg hooked up to ground touches one of the alligator cables, the board resets. Also, I was using a 10k before I saw the second comment. I have a 220 one around. Would that work? And could that perhaps be the issue?
    – Yemi Davis
    May 22 at 16:40

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