Solar Tracking System

SimpleCircuits

Arduino Solar DIY

Renewable Energy Project

Dual-Axis Solar
Tracking System

Build a high-performance solar tracker that follows the sun in real-time. Four LDR sensors, an Arduino UNO, and two servo motors — boosting energy capture by up to 40% versus fixed mounts.

40% More Efficient

4 LDR Sensors

2 Servo Axes

<300mA Power Draw

Finished Build

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System Overview

How the System Works

The tracker reads the sky through four LDR sensors placed around the panel, computes intensity deltas, and drives two SG90 servos in a real-time closed loop — keeping the panel perpendicular to sunlight from sunrise to sunset.

01

Sense

4 LDRs in voltage-divider config stream analog light data to A0–A3.

02

Compare

Arduino computes top/bottom and left/right intensity differences.

03

Decide

If delta exceeds tolerance (90), servo receives a step command.

04

Track

Panel tilts and rotates toward max brightness, loops at 10 ms.

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Bill of Materials

Components Required

Everything you need to build the complete dual-axis tracker. All components are widely available and beginner-friendly.

Component	Qty	Buy
Arduino UNO	1×	Buy Now
Solar Panel (5V–6V)	1×	Buy Now
SG90 Servo Motors	2×	Buy Now
LDR Sensors	4×	Buy Now
10kΩ Resistors	4×	Buy Now
Breadboard + Jumper Wires	1 set	Board Wires
Battery / Power Bank (5V)	1×	Buy Now

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3D Printable Parts

3D Model Files

Download the STL files for the dual-axis bracket, servo mounts, and sensor housing. Print at home or order a professional print through JLCPCB's 3D service.

Download STL Files Order 3D Print — JLCPCB

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Wiring

Circuit Diagram

Connect LDRs at A0–A3 in voltage divider configuration with 10kΩ pull-down resistors. Horizontal servo on pin 2, vertical on pin 13. Power with 5V from Arduino or external USB bank.

🎥

Full assembly tutorial above — step-by-step wiring, servo calibration, and a real-time sun tracking demo from first power-on.

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Firmware

Arduino Code

Upload this sketch to your UNO. The closed-loop algorithm reads all four LDR channels, calculates axis deltas, and steps each servo toward maximum brightness within user-defined angle limits.

solar_tracker.ino — Arduino C++

#include <Servo.h>

Servo horizontal;        // Horizontal Servo Motor
int servohori = 180;
int servohoriLimitHigh = 175;
int servohoriLimitLow  = 5;

Servo vertical;          // Vertical Servo Motor
int servovert = 45;
int servovertLimitHigh = 100;
int servovertLimitLow  = 1;

// LDR pin connections
int ldrlt = A0;  // Bottom Left  LDR
int ldrrt = A3;  // Bottom Right LDR
int ldrld = A1;  // Top Left     LDR
int ldrrd = A2;  // Top Right    LDR

void setup() {
  horizontal.attach(2);
  vertical.attach(13);
  horizontal.write(180);
  vertical.write(45);
  delay(2500);
}

void loop() {
  int lt = analogRead(ldrlt);
  int rt = analogRead(ldrrt);
  int ld = analogRead(ldrld);
  int rd = analogRead(ldrrd);

  int dtime = 10;
  int tol   = 90;  // Tolerance — adjust for sensitivity

  int avt = (lt + rt) / 2;  // Average top
  int avd = (ld + rd) / 2;  // Average bottom
  int avl = (lt + ld) / 2;  // Average left
  int avr = (rt + rd) / 2;  // Average right

  int dvert  = avt - avd;
  int dhoriz = avl - avr;

  if (abs(dvert) > tol) {
    if (avt > avd) {
      servovert = ++servovert;
      if (servovert > servovertLimitHigh) servovert = servovertLimitHigh;
    } else {
      servovert = --servovert;
      if (servovert < servovertLimitLow) servovert = servovertLimitLow;
    }
    vertical.write(servovert);
  }

  if (abs(dhoriz) > tol) {
    if (avl > avr) {
      servohori = --servohori;
      if (servohori < servohoriLimitLow) servohori = servohoriLimitLow;
    } else {
      servohori = ++servohori;
      if (servohori > servohoriLimitHigh) servohori = servohoriLimitHigh;
    }
    horizontal.write(servohori);
  }

  delay(dtime);
}

setup()

Attaches servos on pins 2 & 13. Sets horizontal to 180°, vertical to 45°. 2.5 s warm-up delay ensures stable servo position on power-on.

loop()

Reads 4 LDR values, averages axis pairs, checks delta vs. tolerance. Steps the appropriate servo by ±1° and clamps within safe limits. 10 ms delay smooths movement.

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Performance

Why Dual-Axis Tracking?

A static south-facing panel captures peak power for only a fraction of the day. Dual-axis tracking eliminates that waste by keeping incidence angles near 90° across the full solar arc.

⚡

~40% Higher Yield

Prototype testing showed 38% more charging current versus a fixed panel.

🔄

Fully Open Source

Modify tolerance, limits, or add sensors. Works with any panel size.

☀️

Real-time Response

10 ms loop reacts instantly to clouds, season changes, or angle shifts.

🧠

STEM Education

Perfect for workshops, science fairs, and off-grid renewable demos.

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