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?
It's always better to use MOSFET as a switch (or relay) like this:
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