Turn on and Off Your Things With a Laser! : 9 Steps (with ...
Step 5: Add the LED. Connect to the arduino the LED which will show if the plug is on or off. It is a basic LED connection, simply connect the long leg to a arduino's digital output through a 220 Ohm resistor and the short the ground. Now your arduino can already control the plug. With this you can control the plug with your computer, or add ...