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I'm trying to use an Arduino to switch a monitor's power on and off. I'm going to wire the Arduino to the monitor's power switch. I've tested the power switch with a multimeter, and when pressed, there is a 3.3V current running through it that triggers the power on and off. The monitor itself is takes 12VDC to power. I know that a relay is used when switching larger power sources from a low voltage source so as not to damage the lower voltage source, but since the switch in question only runs at 3.3V would it be safe to use the Arduino without a relay?

  • I think that behind the switch you tested might be already a relay that switches the 12V. – Michel Keijzers Oct 3 '17 at 20:13
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It's always better to use MOSFET as a switch (or relay) like this:

enter image description here

It can handle loads up to 24V, 5A. The load is powered from an external supply. It is based on a IRF520 Mosfet and cost 0.55 a piece in Aliexpress. Search "Arduino IRF520 module"

You need one Arduino pin to switch on/off the load.

It's very handy and provide posts for power input/output.

I understand that you will still power the monitor from the wall, replacing only the original switch with Arduino. Otherwise, you will need a bigger relay

  • The monitor is actually being powered by a 12VDC battery. Will this MOSFET work with DC instead of AC? Could you add a link to where I can get this? Or possibly link to some more information on them? – browntastic Oct 3 '17 at 20:59
  • Well; it's a MOSFET, so it's works only with DC. A MOSFET can only be used to control DC loads since it is a unidirectional switch - current flow can be controlled when it is flowing from drain to source, but can not be controlled from source to drain. Goto aliexpress.com and search "arduino irf520 module". – user31481 Oct 3 '17 at 21:27

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