Arduino is a fantastic tool for controlling temperatures especially freezers. For fermenting beer, a chest freezer is a fantastic platform but the factory controls are far too cold. This controller project effectively overrides those by cutting power to the freezer once it chills to the desired temperature. The controller in this project is further enhanced with a standard electrical outlet and light switch controller.
When the switch is on and the temperature is higher than the thermostat setting, the outlet is powerered. When the switch is turned off, or the temperature drops below the thermostat setting, the outlet is off.
It uses a thermistor to measure the temperature in a freezer it then uploads the temperature to ThingSpeak. It also turns on a buzzer if the temperature is above -18°C.
In the unlikely case that you find the temperature of the freezer to be interesting, you can follow it here: Freezer temperature on ThingSpeak.
Or visit https://hackaday.io/project/3749-wifi-shield-for-arduino-using-an-esp8266-module/log/12427-test-project-freezer-temperature-monitor to learn more about this project.