I am new to Arduino and electronics in general.

I am working on a project where I would ultimately like to power the project from 220V AC (Wall light switch) (I want to replace the light switch with one of my own design).

I will want to feed power to the arduino directly from the 220V connecting wires in the light switch cavity.

This power source is 5V (I know the Arduino needs 9-12V), but I will use a USB connector, wired onto my AC/DC power source, to power the Arduino.

Power Source


AC85 - 264V or  DC110 - 370V wide voltage input
DC 5V(+/ -0.2V) 600mA isolated output
Input Current: 0.0273A/115VAC  0.014A/230VAC
Input surge current: 20A (230VAC)
Frequency range: 50/60 Hz
Operating Temperature: -30 - 70 ℃
Relative humidity: 20%- 90%
Rated power: 3W
Output efficiency: 80%

I don't really know why yet (this is part of figuring that out), but I have the feeling that the arduino would want a linear power source, rather than a switching power source. (Because linear is cleaner power?)

Regardless, I am asking the question as if this power source will do the job, and if not, why not? (Why not a switching PSU) ?

1 Answer 1


Yes, that power supply is ideal for powering an Arduino (an Arduino doesn't care if it's linear or switching, and a linear regulator that goes from 220V to 5V is called a furnace, and you don't want one of those...)

HOWEVER unless you have a very strange wiring setup in your house, under normal circumstances there is no 220V supply in the switch. You normally have live in, switched live out and NO neutral connection.

That means you don't have the connections you need to wire your power supply up to.

By the way: if you didn't already know that then you are not qualified to mess around with home wiring and you should leave it to the professionals.

  • Well well well... I DID indeed forget about that. I am no electrician, and to be honest I have never opened a light socket, but I do know (forgot obviously) that they are not powered by a neutral and positive. I got whisked away so fast on the cool project idea, that I did not consider that. I just wrongly assumed "there must be power there" because it turns the light on. Thanks for getting me back on track! ;-P Commented Feb 23, 2018 at 16:23
  • 1
    actually new code recommends/requires putting a neutral at each switch location exactly to enable smart switches. Commented Feb 23, 2018 at 16:40
  • @ratchetfreak ... depending on where you live... codes aren't universal.
    – Majenko
    Commented Feb 23, 2018 at 16:44
  • Being in South Africa in a rather "long ago built house", I probably do not have a neutral wire in the cavity. I will inspect. Commented Feb 23, 2018 at 17:45
  • in the USA, we've been running neutrals in practice since the 90s and in code since 2011.
    – dandavis
    Commented Feb 23, 2018 at 23:20

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