My friend Fatima of Little Egret Studio was interested to monitor the temperature of her pottery kiln, a SKUTT KM822. We came up with a system that uses the kiln’s built-in K-type thermocouple, and the Blynk app on any phone/tablet to monitor the kiln and studio’s temperatures.
Blynk.cc is a popular system for IoT projects, making it quite easy to send data to their server and create an app to visualise the data. They support ESP8266, and together with the WiFiManager library, it’s easy to configure the hardware for a new wifi network without having to update the code.
My first breadboard prototype used a K-type thermocouple that i had from a previous project (for frying oil and for a friend’s pizza oven, see here). It has a MAX31855 chip, and i used the Adafruit library.
However, this termocouple sensor+wire is only rated for 400degC, and when we tried it in the kiln, only putting the metal tube inside the klin, it worked all the way up to 1200degC and back down. But this did damage the sensor+wire as in below picture (original and used).
As the kiln’s built-in thermocouple is also K-type, we tried to connect our hardware to that sensor, and after verifying that it did not influence the temperature reading by the kiln’s own controller, we chose to use this built-in sensor for our system as well.
Inside our box is the NodeMCU v1 (ESP8266), and the MAX31855 thermocouple breakout, with a 0.01uF cap over the inputs. The thermocouple is connected via a barrel connector plug. We power it from a USB cable, with a 1A fuse. 3 LED for diagnostics. Laser cut box in 2.5mm plywood, put together with hot glue.
The Blynk app below shows the temperature profile as programmed in the kiln, with a book reference on the right.