Arduino Temperature Controller

This code allows an Arduino to work like a PID controller. It uses a MAX6675 with K type thermocouple to turn a heat source (hotplate), to maintain a constant temperature.

This version uses a Adafruit SSD1306 OLED for visual output.

3 inputs are used, temp scale (C/F/K), target temperature up, and target temperature down. Those are simple momentary contact buttons to ground, on 3 analog pins.