Review on Pro Engineered PWM AC Voltage Dimmer 50/60Hz 80-240VAC for Arduino Raspberry - Leading Edge Dimmer for AC Motor, Pump, Fan, Light, Heater - Maximum 500W - Onboard Snubber Circuit - Worldwide Compatibility by Trae Joubert

Pretty straightforward. On the low voltage side you have 5V/3.3V inputs, ground and a PWM signal, on the high voltage side you have an AC input and an AC load, both with the correct labels (Live and Neutral). You plug everything into the appropriate input, THEN turn on the AC circuit (safety first, kids!). Once the board detects the DC circuit (your GPIO pins are properly connected), all the frequency LEDs will flash while the AC power is off. Once your AC circuit is fully and properly connected you will see the board determine the correct frequency for your high voltage AC circuit and only one LED will illuminate to indicate line frequency. Or the closest I suppose. Once everything is set up and ready you shouldn't see any flickering, neither 50Hz in Europe nor 60Hz in America or whatever is used in your country (you know the rules). Then all you have to do is know a few codes and give wings to the little nerd in your heart! I am using this specifically to drive an AC motor and digital speed controller from my Raspberry Pi. You can see them doing something similar with a drill in the description on YouTube. 5 stars overall, I think the board is the perfect size (it's even smaller than my RPi3), doesn't require much knowledge or thought, just a bit of basic electronics and coding, and in case you don't already know. BE SURE! You will be dealing with high voltage alternating current.