🛠️ Project Overview
💡 Objective
🔧 Hardware Required
🎯 What is PID Control
🧠 Software Logic
💻 Code Features
📊 Tuning Approach
🖥️ Display Layout
🔍 Future Enhancements
🎥 Operation & Results

Published November 11, 2025 © MIT

PID-Based LED Brightness Control Using Wio Terminal

This project implements a closed-loop PID control system to adjust the brightness of an LED based on ambient light levels.

BeginnerFull instructions provided1 hour32

PID-Based LED Brightness Control Using Wio Terminal

Things used in this project

Hardware components

Seeed Studio Wio Terminal

LED (generic)

Jumper wires (generic)

Resistor 330 ohm

Solderless Breadboard Full Size

Story

🛠️ Project Overview

This project implements a closed-loop PID control system to adjust the brightness of an LED based on ambient light levels. The Wio Terminal's built-in light sensor continuously monitors the environment, and the PID algorithm dynamically adjusts the LED's PWM output to maintain a target brightness level.

💡 Objective

Maintain total light level at setpoint by compensating ambient light with LED brightness using closed-loop PID control.

🔧 Hardware Required

Wio Terminal Board

Wio Terminal GPIO and Buttons

Wio Terminal GPIO

LED connected to D1 pin on Wio Terminal
Resistor
Breadboard and jumper wires

🎯 What is PID Control?

PID (Proportional-Integral-Derivative) is a control loop feedback mechanism widely used in industrial control systems. It calculates an "error" value as the difference between a desired setpoint and a measured process variable, then applies correction based on three t💡 Objective

Maintain ambient light at setpoint by compensating with LED brightness using feedback from the Wio Terminal's light sensor.erms:

PID (Proportional-Integral-Derivative) Diagram

1. Proportional (P) - Reacts to Current Error

Proportional = Kp × (Target - Current)

What it does: Immediate response to the current error
Effect: Larger errors get larger corrections
Too high: Causes oscillation and instability
Too low: Slow response, never reaches target

2. Integral (I) - Corrects Past Errors

Integral = Ki × ∑(All Past Errors)

What it does: Eliminates steady-state error that persists over time
Effect: Accumulates small errors that the P term misses
Too high: Causes overshoot and windup
Too low: System never quite reaches the target

3. Derivative (D) - Predicts Future Errors

Derivative = Kd × (Current Error - Previous Error)

What it does: Damps the system and reduces overshoot
Effect: Slows down the response when approaching the target
Too high: Makes system sluggish and slow to respond
Too low: Allows oscillation and overshoot

In Our Lighting System:

Error = Target Lux - Current Lux

P Term: If it's too dark, immediately increase LED brightness
I Term: If it stays slightly dark, gradually increase more
D Term: If we're approaching the target, slow down the changes

Tuning Approach:

1. Start with P only (set Ki=0, Kd=0)

2. Increase Kp until the system oscillates, then reduce by 50%

3. Add Ki to eliminate steady-state error

4. Add Kd to reduce overshoot and oscillation

🧠 Software Logic

1. Read Light Sensor: Continuously measure ambient light using the Wio Terminal's built-in sensor.

Sensor Specifications:

Sensor Type: Analog light sensor
Range: 0 to 1023 (10-bit ADC)
0: Complete darkness
1023: Maximum brightness
Location: Built into Wio Terminal

Practical Light Level Examples

2. Compute Error: Calculate the difference between the target light level and the current reading.

3. Apply PID Algorithm:

Proportional: Reacts to current error.
Integral: Accounts for accumulated error over time.
Derivative: Predicts future error based on rate of change.

4. Adjust LED Brightness: Use PWM to control the LED's brightness based on PID output.

5. Visual Feedback:

Real-time light level bar with color coding
Historical data graph
PID parameters display
Current values monitoring

💻 Code Features

Real-time PID control
Interactive display with light bar and historical graph
Button controls:
A: Decrease target (-25)
B: Increase target (+25)
C: Cycle through PID tuning presets

- Serial monitoring for data analysis

When starting the system:

Cover the light sensor → LED lights up brightly
Shine light on the sensor → LED dims down
When reaching target → LED operates at appropriate level

Desired Outcome:

The system tries to maintain ambient light
LED compensates when ambient light is below the set point
LED dims when ambient light is above the set point

📊 Tuning Approach

- Start with moderate P gain (Kp=2.0-3.0)- Add small integral term (Ki=0.1-0.2) for accuracy- Use derivative (Kd=0.5-1.0) to reduce oscillation- Press Button C to test different preset combinations

🖥️ Display Layout

Top: PID parameters and real-time values
Middle: Color-coded light level bar
Bottom: Historical data graph with setpoint line

╔══════════════════════════════════════╗
║        BRIGHTNESS CONTROL            ║  ← Title
╠══════════════════════════════════════╣
║ PID PARAMETERS:     CURRENT VALUES:  ║
║ Kp: 3.0             Target: 500      ║  ← Parameters
║ Ki: 0.20            Light:  350      ║  ← Current Values
║ Kd: 0.8             Output: 180      ║
║                                      ║
║ A: -Target  B: +Target  C: Tune PID  ║  ← Button Instructions
╚══════════════════════════════════════╝
╔══════════════════════════════════════╗
║ Light Level: ██████████░░ 450       ║  ← Light Bar
║                                      ║
║      Light Level Over Time           ║
║    ┌────────────────────────────┐    ║
║    │         ___---___          │    ║  ← Graph
║    │      ___/       \___       │    ║
║    │____--             \--_____ │    ║
║    └────────────────────────────┘    ║
╚══════════════════════════════════════╝

⚠️ Important Note:

The LED should be positioned to NOT directly illuminate the light sensor,

otherwise it creates a feedback loop that destabilizes the system.

🔍 Future Enhancements

Data Logging: Save performance data to SD card for analysis
Wireless Connectivity: Bluetooth/Wi-Fi for remote monitoring and control
PID Auto-Tuning: Implement self-adjusting PID parameters
Smart Features: Time-based schedules and weather adaptation
Mobile Integration: Smartphone app for system management

🎥 Operation & Results

The code

Cover the light sensor → LED lights up brightly

Shine light on the sensor → LED dims down

When reaching target → LED operates at appropriate level

Test code

#include "TFT_eSPI.h"
TFT_eSPI tft;

// PID variables
double Kp = 3.0;
double Ki = 0.2; 
double Kd = 0.8;

double setpoint = 500;
double error = 0;
double lastError = 0;
double integral = 0;
double derivative = 0;
double output = 0;

unsigned long lastTime = 0;
unsigned long sampleTime = 100;

int graphData[60];
int dataIndex = 0;

const int EXTERNAL_LED = D1;

void drawInterface();
void updateDisplay(int lightValue, int output);
void updateGraph(int lightValue);
void drawGraph();
void checkButtons();
void drawLightBar(int lightValue);
void clearDisplayArea(int x, int y, int w, int h);

void setup() {
  tft.begin();
  tft.setRotation(3);
  tft.fillScreen(TFT_BLACK);
  
  pinMode(WIO_LIGHT, INPUT);
  pinMode(WIO_BUZZER, OUTPUT);
  pinMode(EXTERNAL_LED, OUTPUT);
  
  pinMode(WIO_KEY_A, INPUT_PULLUP);
  pinMode(WIO_KEY_B, INPUT_PULLUP);
  pinMode(WIO_KEY_C, INPUT_PULLUP);
  
  Serial.begin(115200);
  
  drawInterface();
}

void loop() {
  unsigned long currentTime = millis();
  
  if (currentTime - lastTime >= sampleTime) {
    int lightValue = analogRead(WIO_LIGHT);
    
    // PID calculation with anti-windup
    error = setpoint - lightValue;
    
    if (!(output >= 250 && error > 0) && !(output <= 5 && error < 0)) {
      integral += error;
    }
    
    integral = constrain(integral, -1000, 1000);
    derivative = error - lastError;
    
    output = Kp * error + Ki * integral + Kd * derivative;
    output = constrain(output, 0, 255);
    
    updateGraph(lightValue);
    updateDisplay(lightValue, output);
    
    analogWrite(EXTERNAL_LED, output);
    
    lastError = error;
    lastTime = currentTime;
    
    Serial.print("Setpoint:");
    Serial.print(setpoint);
    Serial.print(", Light:");
    Serial.print(lightValue);
    Serial.print(", Output:");
    Serial.print(output);
    Serial.print(", Error:");
    Serial.println(error);
  }
  
  checkButtons();
  delay(10);
}

void drawInterface() {
  tft.fillScreen(TFT_BLACK);
  
  // Title at top
  tft.setTextColor(TFT_CYAN);
  tft.setTextSize(2);
  tft.setCursor(70, 5);
  tft.println("BRIGHTNESS CONTROL");
  
  // Separator line
  tft.drawFastHLine(0, 30, 320, TFT_DARKGREY);
  
  // Left column - PID parameters
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(1);
  tft.setCursor(10, 35);
  tft.println("PID PARAMETERS:");
  tft.setCursor(10, 50);
  tft.print("Kp: "); tft.println(Kp, 1);
  tft.setCursor(10, 65);
  tft.print("Ki: "); tft.println(Ki, 2);
  tft.setCursor(10, 80);
  tft.print("Kd: "); tft.println(Kd, 1);
  
  // Right column - Real-time values (headers only)
  tft.setCursor(180, 35);
  tft.println("CURRENT VALUES:");
  
  // Button instructions at bottom of text area
  tft.setTextColor(TFT_YELLOW);
  tft.setTextSize(1);
  tft.setCursor(10, 100);
  tft.println("A: -Target  B: +Target  C: Tune PID");
  
  // Draw initial static elements for light bar and graph
  drawLightBar(0);
  drawGraph();
}

void updateDisplay(int lightValue, int output) {
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(2);
  
  // Update real-time values (right column)
  clearDisplayArea(180, 50, 130, 45);
  
  tft.setTextSize(1);
  tft.setCursor(180, 50);
  tft.print("Target: "); tft.println(setpoint);
  
  tft.setCursor(180, 65);
  tft.print("Light:  "); tft.println(lightValue);
  
  tft.setCursor(180, 80);
  tft.print("Output: "); tft.println(output);
  
  // Update light bar and graph (below all text)
  drawLightBar(lightValue);
  drawGraph();
}

void clearDisplayArea(int x, int y, int w, int h) {
  tft.fillRect(x, y, w, h, TFT_BLACK);
}

void drawLightBar(int lightValue) {
  int barWidth = map(lightValue, 0, 1023, 0, 250);
  int barHeight = 15;
  int barX = 35;
  int barY = 120;  // Moved below all text
  
  // Clear bar area
  tft.fillRect(barX, barY, 255, barHeight + 5, TFT_BLACK);
  
  // Bar background
  tft.fillRect(barX, barY, 250, barHeight, TFT_DARKGREY);
  
  // Bar foreground with color coding
  uint16_t barColor;
  if (lightValue < 300) barColor = TFT_RED;
  else if (lightValue < 700) barColor = TFT_YELLOW;
  else barColor = TFT_GREEN;
  
  tft.fillRect(barX, barY, barWidth, barHeight, barColor);
  tft.drawRect(barX, barY, 250, barHeight, TFT_WHITE);
  
  // Bar label
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(1);
  tft.setCursor(10, barY + 3);
  tft.print("Light Level:");
  tft.setCursor(barX + 255, barY + 3);
  tft.print(lightValue);
}

void updateGraph(int lightValue) {
  graphData[dataIndex] = lightValue;
  dataIndex = (dataIndex + 1) % 60;
}

void drawGraph() {
  int graphHeight = 70;
  int graphWidth = 280;
  int graphX = 20;
  int graphY = 145;  // Moved below light bar
  
  // Clear graph area
  tft.fillRect(graphX, graphY, graphWidth + 5, graphHeight + 5, TFT_BLACK);
  
  // Graph border
  tft.drawRect(graphX, graphY, graphWidth, graphHeight, TFT_DARKGREY);
  
  // Setpoint line
  int setpointY = graphY + graphHeight - map(setpoint, 0, 1023, 0, graphHeight);
  tft.drawLine(graphX, setpointY, graphX + graphWidth, setpointY, TFT_GREEN);
  
  // Graph data lines
  for (int i = 0; i < 59; i++) {
    int currentIndex = (dataIndex + i) % 60;
    int nextIndex = (dataIndex + i + 1) % 60;
    
    int x1 = graphX + map(i, 0, 59, 0, graphWidth);
    int x2 = graphX + map(i + 1, 0, 59, 0, graphWidth);
    
    int y1 = graphY + graphHeight - map(graphData[currentIndex], 0, 1023, 0, graphHeight);
    int y2 = graphY + graphHeight - map(graphData[nextIndex], 0, 1023, 0, graphHeight);
    
    tft.drawLine(x1, y1, x2, y2, TFT_BLUE);
  }
  
  // Graph title
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(1);
  tft.setCursor(graphX, graphY - 10);
  tft.print("Light Level Over Time");
}

void checkButtons() {
  static unsigned long lastButtonPress = 0;
  
  if (millis() - lastButtonPress > 200) {
    if (!digitalRead(WIO_KEY_A)) {
      setpoint = constrain(setpoint - 25, 100, 900);
      lastButtonPress = millis();
      tone(WIO_BUZZER, 800, 50);
      integral = 0;
    }
    
    if (!digitalRead(WIO_KEY_B)) {
      setpoint = constrain(setpoint + 25, 100, 900);
      lastButtonPress = millis();
      tone(WIO_BUZZER, 1200, 50);
      integral = 0;
    }
    
    if (!digitalRead(WIO_KEY_C)) {
      // Cycle through PID presets
      static int tuneState = 0;
      tuneState = (tuneState + 1) % 4;
      
      switch(tuneState) {
        case 0: Kp = 2.0; Ki = 0.1; Kd = 0.5; break;
        case 1: Kp = 3.0; Ki = 0.2; Kd = 0.8; break;
        case 2: Kp = 5.0; Ki = 0.3; Kd = 1.2; break;
        case 3: Kp = 1.0; Ki = 0.05; Kd = 0.2; break;
      }
      
      integral = 0;
      lastButtonPress = millis();
      tone(WIO_BUZZER, 2000, 100);
      
      // Update PID display
      tft.setTextColor(TFT_WHITE);
      tft.setTextSize(1);
      tft.fillRect(10, 50, 80, 40, TFT_BLACK);
      tft.setCursor(10, 50);
      tft.print("Kp: "); tft.println(Kp, 1);
      tft.setCursor(10, 65);
      tft.print("Ki: "); tft.println(Ki, 2);
      tft.setCursor(10, 80);
      tft.print("Kd: "); tft.println(Kd, 1);
    }
  }
}

Credits

Aula Jazmati 💡🕊️

67 projects • 232 followers

Electronic Engineering

PID-Based LED Brightness Control Using Wio Terminal

Things used in this project

Hardware components

Story

🛠️ Project Overview

💡 Objective

🔧 Hardware Required

🎯 What is PID Control?

🧠 Software Logic

💻 Code Features

📊 Tuning Approach

🖥️ Display Layout

🔍 Future Enhancements

🎥 Operation & Results

Code

Test code

Wio-Terminal-Codes

Credits

Aula Jazmati 💡🕊️

Comments

Embed the widget on your own site

PID-Based LED Brightness Control Using Wio Terminal

PID-Based LED Brightness Control Using Wio Terminal

Things used in this project

Hardware components

Story

🛠️ Project Overview

💡 Objective

🔧 Hardware Required

🎯 What is PID Control?

🧠 Software Logic

💻 Code Features

📊 Tuning Approach

🖥️ Display Layout

🔍 Future Enhancements

🎥 Operation & Results

Code

Test code

Wio-Terminal-Codes

Credits

Aula Jazmati 💡🕊️

Comments

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