Controlling Servo by Detection of AC voltage signal

I have a need to program an Arduino to detect when a standard 125 VAC plug has power supplied to it, so that it knows when that voltage signal is present it should send a signal to a servo to move a plastic arm to a specific location. When the signal is not present, then it should return the arm to the previous pre-set position.

I've thought of using either a relay or current sensor to approach this, but need the project to be as simple as possible.

Any pointers?

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cjmccorm3:
I have a need to program an Arduino to detect when a standard 125 VAC plug has power supplied to it, so that it knows when that voltage signal is present it should send a signal to a servo to move a plastic arm to a specific location. When the signal is not present, then it should return the arm to the previous pre-set position.

I've thought of using either a relay or current sensor to approach this, but need the project to be as simple as possible.

Any pointers?

Try this.
It will keep you away from direct connections to the AC supply voltages.

One of these wired to digital input is pretty doggone simple.