Light tracing

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY

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.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	Digital Servo Motor	1	BUY
6	Photoresistor Module	1	BUY

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.h>

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
}