Arduino PID Temperature Controller using MAX6675 K-Thermocouple to Digital Converter IC

This project implements a closed-loop temperature control system using an Arduino Nano as the central processing unit. Thermal feedback is gathered by a K-type thermocouple, which generates a small voltage proportional to temperature. Because this voltage is extremely weak and nonlinear, it is fed into a MAX6675 module. The MAX6675 digitizes the analog thermocouple signal via an SPI interface and provides cold-junction compensation, allowing the Arduino to read precise temperature values. The Arduino Nano runs a PID (Proportional-Integral-Derivative) algorithm that continuously compares the measured temperature against a target setpoint. Based on the error between these two values, the PID algorithm calculates an output correction signal. This output is typically driven as a pulse-width modulation (PWM) signal through a MOSFET, which acts as an electronic switch to regulate the high current flowing into a heating element. User interaction—such as adjusting the target temperature setpoint—is handled locally via a generic rotary encoder. Visual feedback, including real-time current temperature, target setpoint, and PID status, is rendered dynamically on a 128x64 OLED display connected to the microcontroller. The entire circuit is prototyped on a breadboard using jumper wires to interconnect the Nano, MAX6675, OLED, and user controls.