The brains of the operation is an STM8S103F module, aka the Blue Pill, which is paired with a DS18B20 temperature sensor. [Tim]’s original coaster has one in a TO-92 package embedded in the top layer, but ultimately he went with the probe version as it reads a truer temperature by...
If you want to learn how a relay module works, read our MicroPython Guide: DS18B20 with ESP32 and ESP8266 (Temperature Readings).We have similar guides using Arduino IDE:ESP32 DS18B20 Temperature Sensor with Arduino IDE (Single, Multiple, Web Server) ESP8266 DS18B20 Temperature Sensor with ...