In traditional displays — and electronics in general — the device’s temperature is normally a side effect, not what actually drives it. In this thermochromic display by hacker ‘Zaphunk,’ the temperature of each display segment is actually used to change it from a black off state, to a greenish hue to indicate temperature or humidity. The digit configuration is the same as a 7-segment LED/LCD setup, with three extra segments used to form either a percent or degree sign.
Conditions are sensed with a DHT22 temp/humidity unit, and everything is powered by six— yes , six — Arduino Nanos, and nine TB6612FNG dual motor drivers. In this configuration, one Nano acts as the master device, which passes info to the other five via I2C. This many controller units were needed for the 18 Peltier elements used, each of which require five digital IO pins and a pair of PWM outputs for temperature control.
Naturally, the wiring for this project was “a total nightmare.” As seen in the video below, however, the results are quite pretty, slowly changing state to show ambient conditions. Code is available on GitHub, and if you’re wondering, the irony of having the device display the ambient temperature by altering its own temperature isn’t lost on Zaphunk.