When making homemade bread, it is important to leave the dough to proof for a while before baking. The temperature the dough is left at during the proofing period is quite important so ideally a temperature controlled container should be used. Bread proofing boxes can be bought online but I made one out of a spare slow cooker and a Sonoff S20 Smart Plug which I flashed with Tasmota.

I am using an old slow cooker which has basic analog temperature controls (low, medium, high, and “keep warm”) with the inner ceramic pot removed. The metal base plate of the slow cooker is exposed and the heating element is directly below so the metal heats up quickly; a DS18B20 temperature sensor is placed against the metal to read the temperature of the hottest part. The temperature sensor is connected to a bus of sensors we have in and around the kitchen and the data is collected by an ESP8266. The dough is placed in a glass bowl which is then stood on the metal. A Sonoff S20 Smart Plug turns the slow cooker on and off.

This method allows the slow cooker to be “repurposed” for cooking again instead of bread proofing. It may be possible to embed a microcontroller inside the slow cooker body which can take control of the temperature/power switch. If this was combined with a temperature sensor, a self-contained bread proofing box could be made. This would likely make the slow cooker unsuitable for normal slow cooking again in the future though.

The temperature of the slow cooker is transmitted to Node-Red on my home server every 20 seconds. A flow is executed within Node-Red to determine when to turn the S20 Smart Plug on or off. Everything is fully customisable so it is possible to configure an exact temperature to maintain or a small temperature range to keep within.