The hardware

Disclaimer:

This is not a step-by-step description of the project.
You can take inspiration by it only if you know what you are doing.
You can use ALL the code and information.
If you aren't an expert don't try to build this device. You do it at your own risk.

List of materials

If you want to build a similar device, you need following hardware and electronics:

• a wooden box
• some styrofoam
• a terrarium heater for reptiles and spiders. Don't use aquarium water heater, it can be dangerous.
• a PC fan
• two small magnets
• a bar for magnetic stirrer
• a plastic tube.
• an airlock for beer/brewing
• two temperature sensor for Arduino
• a relay for 220 volts
• breadboard and basic electronics components and tools

In my system I have also installed a white led and a photoresistor. The idea was to measure the transparence of the liquid, but it ended to be a useless idea. Don't do it.