PID Controller in C

A lightweight PID controller implementation in C, simulating a temperature control system.

Theory

A PID controller corrects the deviation between a desired value (setpoint) and a measured value (measurement) using three terms:

• P (Proportional): Reacts to the current error. Larger error = larger correction.
• I (Integral): Accumulates past errors to eliminate steady-state offset.
• D (Derivative): Reacts to the rate of change of the error to reduce overshoot.

Output: y = Kp*e + Ki*∑e*dt + Kd*(de/dt)

Project Structure

pid-controller-c/
├── include/pid.h       # PID struct and function declarations
├── src/pid.c           # PID implementation (init, update, anti-windup)
├── src/main.c          # Temperature simulation loop
├── src/gui.c           # GTK3 desktop UI with live response curve
├── test/test_pid.c     # Unit tests (coming soon)
└── CMakeLists.txt      # Build configuration

Dependencies

• GCC
• CMake 3.16+
• GTK3 (for the GUI)

sudo apt install cmake gcc libgtk-3-dev

Build & Run

CLI simulation:

mkdir build && cd build
cmake ..
make
./pid_sim

GTK GUI:

cd build
make pid_gui
./pid_gui

GUI Usage

1. Set Kp, Ki, Kd using the input fields
2. Set a Setpoint (target value)
3. Click Run Simulation
4. The response curve shows:
   • 🟢 Green line — Setpoint (target)
   • 🔵 Blue curve — Process Variable (system response)

Tuning

Parameter	Effect
Kp	Speed of response. Too high = oscillation.
Ki	Eliminates steady-state error. Too high = overshoot.
Kd	Reduces overshoot. Too high = instability.