I have a situation where I need to power an Arduino Uno R3 from a ~16V power supply.

The problem is I have no idea of the implications of voltage dropping. I think I just need a 100 Ohm resistor.

So, in case I am right, my actual question turns into: When is it better to complicate a circuit with a Zener diode?

I will also attach a photo since I understand it is easier to read from it.

enter image description here

Edit 1: A neighbor suggested a 4V LED that would also indicate it's working.

  • 3
    \$\begingroup\$ Don't use a voltage divider (resistors) or a zener. Use a DC/DC converter \$\endgroup\$
    – Huisman
    Commented Jul 26, 2019 at 6:57
  • \$\begingroup\$ Read This SE EE question and then this answer and you should have a VERY good idea of what to do. The other answers are also useful - the above one is mine :-). \$\endgroup\$
    – Russell McMahon
    Commented Jul 26, 2019 at 13:23
  • \$\begingroup\$ Reducing the Vin to theUNO to closer to the processor operating voltage will reduce the heat in the onboard regulator. \$\endgroup\$
    – Russell McMahon
    Commented Jul 26, 2019 at 13:24

1 Answer 1


If you need to power it, it is not a good idea. What happens, if your Arduino suddenly draws more current? -> The voltage drop across your resistor increases, the voltage on your Arduino supply decreases. Same case with diode.

Use a simple linear regulator or a switching DC/DC converter module.

  • \$\begingroup\$ ... and we usually use the battery negative as the common or GND (and not the positive). \$\endgroup\$
    – Transistor
    Commented Jul 26, 2019 at 6:56
  • \$\begingroup\$ this is why it's best to ask, thank you \$\endgroup\$
    – Joita Dan
    Commented Jul 26, 2019 at 7:23

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