120v trigger or startup

So new to the arduino world. Background is, run a Christmas light display. It is a computer based controller that turn on and off 120v outlets. We are looking to add an animatronic aspect controlled by an arduino. I see potentially two options, just not sure on which is easier or better option.

  1. have computer send 120v signal to trigger arduino input. I understand that arduino cannot accept 120v on the input pins. So would have to reduce volts down, somehow.

  2. have arduino plugged into outlet from computer system. Computer system turns on outlet> powering up arduino > arduino triggers events on startup.

Any help is appreciated.

I sincerely hope you live to see Christmas in.

Seriously, buy an approved device, or hire someone that knows what they’re doing with mains voltage on microcontrollers.

Generally speed is not important to me so I use small 5V wall warts as voltage sensors. If unregulated I use 3.5. I then add a 1K resistor across the output and a 47K resistor in series with the arduino pin with grounds being connected. The 1K resistor discharges the wall wart when its power is removed. The 47K protects the input of the Arduino, anything between 2K and 100K should work. Just because there is mains voltage you do not have to mess with it the wall wart isolates everything including you!