Ha. I modified my Whirlpool dryer with an Arduino-based automation because its own internal sensor is not precise. I used this nice sensor: https://www.adafruit.com/product/4099
Mine has metal contacts in the back of the drum, which I presume measures resistance, similar to how this soil moisture sensor works: https://www.adafruit.com/product/6362
I'll never understand how modern designs work worse, despite access to better sensors.
