Light tracing

Course Introduction

This Arduino project uses an LDR to detect ambient light changes and control a servo. The original code supports two LDRs, but this experiment uses only one. You can try adding a second LDR for further exploration.

The servo adjusts its angle based on light intensity, simulating responsive movement. A tolerance threshold reduces jitter from small changes. This system is ideal for light-following robots or sun trackers.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Wiring

Common Connections:

Digital Servo Motor
Connect to breadboard’s positive power bus.
Connect to breadboard’s negative power bus.
Connect to 9 on the Arduino.

Photoresistor Module
A0: Connect to A0 on the Arduino.
If there is another light-dependent resistor (LDR), then A0 Connect to A1 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Writing the Code

Note
You can copy this code into Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

#include 

Servo myServo;

const int ldrLeft = A0;
const int ldrRight = A1;

int servoPin = 9;
int pos = 90; // Initial angle centered
int tolerance = 10; // Threshold to reduce jitter
void setup() {
  myServo.attach(servoPin);
  myServo.write(pos);
  Serial.begin(9600);
}

void loop() {
  int leftValue = analogRead(ldrLeft);
  int rightValue = analogRead(ldrRight);

  int difference = leftValue - rightValue;

  Serial.print("Left: ");
  Serial.print(leftValue);
  Serial.print(" | Right: ");
  Serial.print(rightValue);
  Serial.print(" | Diff: ");
  Serial.println(difference);

  if (abs(difference) > tolerance) {
    if (difference > 0 && pos < 360) {
      pos++;
    } else if (difference < 0 && pos > 0) {
      pos--;
    }
    myServo.write(pos);
  }

  delay(20); // Proper delay to avoid movement too fast
}