• NodeMcu 1.0 Board or D1 mini
• Relay Board, two way recommended.
• Two DS18B20 sensors
• 4.7K resistor.
• [Optional] 20×4 I2C LCD
• [Optional] TWO pushdown buttons
• Power supply to ESP8266. (I use a USB adapter) 1.5+A is recommended.
• Power cable, sockets, project box, and etc.

This the simplest setup which mixes 5v and 3.3v circuits. It might not be a good practice, but it works. I have been using this for more than one year. Some additional notes:

• LCD and buttons are good to have. You will be able to operate it without a computer or phone.
• SSD1306 based 128x64 I2C OLED LCD can be used in place of the 20x4 LCD. They are small and cheap.
• One addition sensor can be used as room temperature sensors. (more than three is useless.)
• Some relay modules might not work under 3.3v. All of mine work, though.
• Some DS18B20 waterproof sensors, especiallly from Amazon, support only parasitic power mode. The sensors run in Parasitic mode are not stable, so BrewPi, hence BrewPiLess, doesn’t support parasitic power mode. The sensors can be detected by other sketches, but BrewPi(less) won’t recognize them