Solar Panel Dual-Axis Sun Tracker using LDR and Servo Motors

A fixed solar panel spends most of the day misaligned with the sun: it faces one direction while the sun arcs across the sky, so the angle of incidence is only near-ideal for a short window around noon. The physics is simple — a panel collects most when sunlight strikes it close to perpendicular — and solar farms recover that lost window with tracking mounts that follow the sun. But commercial trackers are expensive closed systems, and in college labs the tracking principle is usually only a diagram on a slide. This project makes it tangible: a working dual-axis tracker built from a small PV panel, four LDR sensors, two hobby servos and an Arduino. The student builds the gimbal, wires the sensor bridge, writes the tracking logic with hysteresis, and runs the calibration procedure — learning feedback control, sensor differential measurement and mechanical drive design in one build.

1. Four LDRs sit in a cross pattern on a small board, separated by a cardboard shadow divider; when the panel is off-sun, the divider shades some LDRs and the readings differ.
2. The Arduino samples the four LDRs through voltage dividers and computes the left-right and top-bottom differences.
3. If a difference exceeds the deadband, the firmware steps the corresponding SG90 servo toward the brighter side by a small increment.
4. The loop repeats every few hundred milliseconds; when all pairs balance within the deadband, the panel holds — that is the sun-facing position.
5. The cycle continues through the day, so the panel re-aims itself as the sun moves.
6. In manual mode, serial commands or buttons drive each axis directly for testing and demonstration.
7. The LCD continuously displays the four sensor values and the current axis positions.

Tech stack:

• Arduino Uno (ATmega328P)
• 4x LDR sensors in cross arrangement with shadow divider
• 2x SG90 servo motors (pan + tilt)
• Small polycrystalline PV panel (design approx. 5 W)
• Plywood dual-axis gimbal frame
• 16x2 character LCD
• Arduino IDE (C/C++ firmware)
• 5 V regulated power supply

• [Dual-axis tracking] Pan and tilt axes let the panel follow the sun in both azimuth and elevation, unlike single-axis trackers that only correct one plane.
• [Four-LDR differential sensing] LDRs in a cross arrangement with a shadow divider compare light levels; the Arduino drives the axes until all four readings balance, which is the sun-facing position.
• [Servo-driven gimbal] Two SG90 servos move the panel through the wooden gimbal frame — a visible, examinable mechanism rather than a black box.
• [Deadband anti-hunting] Firmware compares sensor pairs against a configurable deadband so the servos settle instead of oscillating around the balance point.
• [Manual override mode] A push-button or serial command switches to manual positioning for viva demonstrations and for testing the mechanics without sunlight.
• [Live status readout] A 16x2 LCD shows the four LDR readings and the current pan/tilt state during operation.
• [Buyer-run calibration] The build ships with a calibration procedure: centering the servos, trimming LDR balance and setting the deadband on the student's own hardware.

• Working dual-axis sun tracker prototype (gimbal, panel, LDR board, servos, Arduino, LCD)
• Complete firmware source code (tracking loop, deadband, manual mode, LCD)
• Wiring and assembly documentation for the gimbal and sensor board
• Calibration procedure (servo centering, LDR trim, deadband setting)
• Project report PDF (tracking theory, sensor bridge design, methodology, test procedure)
• PPT presentation for final review
• Viva Q&A preparation document (feedback control, differential sensing, servo control)
• Setup and demonstration guide