PID-Therm: Automated Temperature Control System 🌡️

An Arduino-based environment controller that uses a PID algorithm to maintain a target temperature with high precision. This project manages a heating element (incandescent bulb) and a cooling system (DC fan) through a full cycle: Heating, Holding, and Cooling.

🚀 Key Features

• PID Control: Real-time calculation of power output to minimize temperature error and overshoot.
• Full Process Cycle: Automated transitions between Heating, Holding, and Cooling phases.
• On-Board Menu: Configure target temperature (TSET), Phase Timers, and PID Constants (Kp, Ki, Kd) using 4 physical buttons.
• LCD Interface: Real-time monitoring of current temperature vs. setpoint.
• Hardware Protection: Implementation of PWM constraints and anti-windup for the integral term.

🛠️ Hardware Requirements

⚠️ Simulation vs. Physical Build

Please note that while the logic remains the same, there are key hardware differences between the Tinkercad simulation and the Physical build:

• Temperature Sensor: - Simulation: Often uses the TMP36 (which requires a 500mV offset in code).
  • Physical: Uses the LM35, which provides a direct $10mV/°C$ output without the offset, offering better accuracy for this specific application.
• Motor Driver: - Simulation: Uses the L293D integrated circuit.
  • Physical: Uses the L298N Module. The physical module includes a heatsink and dedicated power terminals, which are essential for handling the current required by the incandescent bulb and fan.
• Wiring & Pins: Pinouts on the L298N module differ from the L293D chip. Ensure you follow the physical module's labels (ENA, IN1, IN2, etc.) as reflected in the provided code.

| Arduino Uno | | LM35 | High-precision analog temperature sensor ($10mV/°C$). | | L298N / L293D | Dual H-Bridge motor driver for power management. | | 12V Bulb | Heating element (controlled via PWM). | | DC Fan | Active cooling element. | | LCD 16x2 | Displays status and menu interface. | | 4x Buttons | Navigation (Plus, Minus, OK, Cancel). |

🧠 The Control Logic (PID)

The system calculates the heater power ($u(t)$) based on the error between the setpoint and current temperature:

$$u(t) = K_p e(t) + K_i \int_0^t e(\tau) d\tau + K_d \frac{de(t)}{dt}$$

• P (Proportional): Reacts to the current error.
• I (Integral): Corrects long-term steady-state errors.
• D (Derivative): Prevents overshoot by reacting to the rate of change.

⚙️ Installation & Usage

1. Hardware: Connect the components according to the wiring diagram from Tinkercad in the /media folder.
2. Software: Upload the .ino file from the /src folder to your Arduino Uno using the Arduino IDE.
3. Power: Connect a 12V power supply to the H-Bridge motor driver.
4. Operation: - Use Plus/Minus to navigate the menu.
   • Use OK/Cancel to adjust values.
   • Select "Start Program" to begin the automated cycle.

💡 Lessons Learned (The "Breadboard Trap")

One major takeaway from this build was discovering that some long breadboards have split power rails. If the sensor or buttons behave erratically, ensure the ground and 5V lines are bridged across the middle of the board. This project uses a Common Ground strategy to ensure signal stability between the Arduino, the H-Bridge, and the external power source.

📜 License

This project is licensed under the MIT License - feel free to use it and modify it for your own needs!