This Maker created an Arduino-powered, servo-based device to turn his AC unit on and off.
If you want to control AC power with an Arduino or other platform, the simplest way is (normally) to use a relay. In Tyler Bletsch’s case, he moved into a new office with a manually-controlled air conditioning unit. As he puts it, “I’m not going to put up with a hot office in the morning, nor will I let the unit blow cold air all night and weekend when nobody’s around. Instead, I will build some crap.”
Well said. Since it’s generally a good idea to keep office equipment unmodified, this “crap” took the form of an Arduino Nano (ATmega328)-controlled servo to physically turn the switch on and off — as seen in the video below. This could, we suppose, be considered to be a very complicated form of a physical relay.
An interesting feature is that, since the horn swings out of the way when not in use, you can flip the switch manually “like a barbarian.” According to Bletsch, the bracket allows control of any U.S. standard wall switch. Because of this flexibility, you should be able to use this technique to control nearly anything, though it usually makes many folks uneasy to automatically power things when they’re not around.
Additionally, the interface consisted of a few tactile buttons and an OLED screen, which displays information like the day and time. In terms of software, he used the Time Library for real-time clock logic, the Adafruit GFX Library to show pixels, and the Native Servo Library to run the servo.