Solar tracker with ARDUINO or ESP32 and soltrack-2.2 library

Warning: This project is still in development.

CAD files: The SolidWorks files are available in the provided zip file. You can use them to simulate the panel's movement and 3D print the required parts. The software is designed to be adaptable to any solar panel, so feel free to modify it to suit your specific needs.

The system computes the sun’s position using the SolTrack 2.2 library. This project supports two microcontrollers: Arduino and ESP32.

Features

Feature	Arduino	ESP32
Microcontroller	Arduino UNO/MEGA2560	ESP32
Time Management (RTC)	Manual adjustment of date and time	Automatic adjustment via Wi-Fi
Wi-Fi Connectivity	Not available	Available
MQTT Support	Not available	Fully supported for Home Assistant
Motor Control (Azimuth/Elevation)	Supported	Supported
Joystick Control	Supported	Supported
Anemometer	Supported	Supported
Solar Position Calculation	Supported	Supported

how it works

Azimuth Control Overview

The azimuth controller manages the solar panel's horizontal movement, powered by a motor controlled via a BTS7960 driver. A southward limit switch acts as a reference to stop the motor when the panel reaches the defined position, preventing excessive rotation.

Pin Configurations

Component	Arduino	ESP32
Motor Enable Pin	Pin 4	GPIO 19
PWM Left (Move Left)	Pin 6	GPIO 18
PWM Right (Move Right)	Pin 5	GPIO 17
Limit Switch	Pin 7	GPIO 16

Calibration and Movement

At startup, the solar tracker goes through a calibration process to measure how long it takes for the panel to rotate fully from one side to the other (from 0° to 360° azimuth). Once calibrated, the tracker is able to adjust the azimuth angle by calculating the time needed to reach the desired position. The system also checks if the target azimuth angle is within the allowed range (AZIMUTH_DEG_MIN to AZIMUTH_DEG_MAX). If outside, the movement is canceled.

Limit Switch

The limit switch ensures the panel doesn’t exceed its bounds, defining 0° (or 360°) when pressed. If triggered during operation, the motor stops immediately. It also acts as a reference point to determine the panel's azimuth angle.

Here is a summary of the azimuth control parameters, as defined in config.h:

Parameter	Value
AZIMUTH_MOTOR_PIN_EN	Motor enable pin
AZIMUTH_MOTOR_PWM_PIN_L	Motor PWM pin for left
AZIMUTH_MOTOR_PWM_PIN_R	Motor PWM pin for right
AZIMUTH_LIMIT_SWITCH_PIN	Limit switch pin
AZIMUTH_DEG_MAX	275.0° (maximum azimuth allowed)
AZIMUTH_DEG_MIN	90.0° (minimum azimuth allowed)
AZIMUTH_TIME_THRESHOLD	Minimum time threshold (optional)

Elevation Control Overview

The elevation controller manages the solar panel’s vertical tilt, tracking the sun's altitude. This is done via an actuator controlled by a BTS7960 motor driver.

Note: Relay or H-Bridge could work, I used a BTS7960 cause i had one laying around.

Pin Configurations for Arduino and ESP32

Component	Arduino	ESP32
Motor Enable Pin	Pin 8	GPIO 26
PWM Up (Extend)	Pin 10	GPIO 27
PWM Down (Retract)	Pin 9	GPIO 14

Calibration and Movement

To ensure correct actuator operation, use the datasheet to configure ELEVATION_ACTUATOR_SPEED and ELEVATION_ACTUATOR_LENGTH. These parameters calculate the time required to fully extend or retract the actuator. If real-world conditions vary, override this time using the FORCE_TIME_FULL_TRAVEL parameter.

Warning: Keep the PWM speed at 255 (maximum) for accurate time calculations during extension and retraction.

At initialization, the system calibrates the actuator, setting the panel to a 90° (horizontal) position for safety. The elevation range is constrained by the actuator’s length and physical limits of the panel. Customize ELEVATION_DEG_MIN and ELEVATION_DEG_MAX based on your setup.

I used SolidWorks to simulate the panel’s movement and constraints.

Key Parameters in config.h

Parameter	Value
ELEVATION_MOTOR_PIN_EN	Motor enable pin
ELEVATION_MOTOR_PWM_PIN_U	PWM pin for extension (up)
ELEVATION_MOTOR_PWM_PIN_D	PWM pin for retraction (down)
ELEVATION_DEG_MAX	90.0°
ELEVATION_DEG_MIN	19.0°
ELEVATION_MOTOR_PWM_SPEED	255 (maximum motor speed)
ELEVATION_ACTUATOR_SPEED	5 mm/s
ELEVATION_ACTUATOR_LENGTH	350 mm
FORCE_TIME_FULL_TRAVEL	Forced full travel time (in seconds)

Anemometer Control Overview

The anemometer is a 3-wire sensor that operates independently from the solar tracker. It monitors wind speeds and ensures the safety of the solar panel during high wind conditions. When the wind speed exceeds 5 m/s, the anemometer activates a relay, sending an alarm signal to the solar tracker.

The solar tracker continuously monitors the alarm signal through a dedicated GPIO pin. If the wind speed exceeds 5 m/s, the tracker moves the solar panel to a safety position for 15 minutes. If the wind speed remains high and the alarm is triggered again during this countdown, the 15-minute timer resets. The panel remains in the safety position until wind conditions stabilize.

Pin Configuration for Anemometer

Component	Arduino	ESP32
Wind Alarm Detection Pin	Pin 11	GPIO 13

Key Parameters in config.h

Parameter	Value
ANEMOMETER_BUTTON_PIN	Pin for alarm detection
ANEMOMETER_SAFE_DURATION	15 minutes (900,000 ms)

Here’s an updated version of the Joystick Control Overview:

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Joystick Control Overview

The joystick allows manual control of the solar panel's movement. By moving the joystick, the user can command the system to adjust the panel’s azimuth (horizontal) and elevation (vertical) angles, according to the inputs detected on the VRX and VRY pins. Additionally, user have to press the joystick button for 5 seconds to enable the joystick control. Same action to disable it.

Pin Configuration for Joystick

Component	Arduino	ESP32
VRX Pin (Horizontal)	A0	GPIO 32
VRY Pin (Vertical)	A1	GPIO 33
Button Pin (Switch)	Pin 2	GPIO 25

MQTT Support Overview

The MQTT protocol is used to communicate with the Home Assistant platform. The solar tracker publishes data to the MQTT broker, which is then read by Home Assistant to display the solar panel’s information. The system has been made with automatic discovery, allowing Home Assistant to recognize the solar tracker and its entities.

Hardware Used

This is a non-exhaustive list of the components used in this project:

Component	Link
ESP32 Devkit	https://www.amazon.fr/dp/B0CLD28SHQ
ESP32 Expansion Board	Delivered with the ESP32 Devkit
2x BTS7960 Motor Drivers	https://www.amazon.fr/dp/B09MHNG2JS
RTC DS3231	https://www.amazon.fr/dp/B077XN4LL4
Joystick	N/A
Anemometer	N/A
DC Motor 12V	N/A
Linear Actuator	https://www.amazon.fr/dp/B0CWN28GFL
Limit Switch TZ-8122	N/A

The Solar Tracker Structure

wooden frame

The wooden frame is a custom-made structure that is designed to hold and position two solar panels. It is constructed using 6 separate pieces of wood that are joined together to form a sturdy base. The Wood Support is an essential component of the Solar Tracker system, as it provides a stable platform for the panels to rest on. The Wood Support is designed to accommodate solar panels with a total size of 1605mm x 2176mm, and provides a total area of 1.73 square meters of surface area for capturing the sun's energy.

The frame is composed of 6 pieces with the following dimensions:

• 68x68x2245 mm
• 68x68x2109 mm
• 68x68x1544 mm

The mast

The mast is divided into two parts to facilitate the azimuth rotation of the wooden frame. The elevation rotation is achieved through the use of two complete ball bearings (SKF UCP 207).

The mast stands at a height of 1.70m.

Special thanks to the SolTrack library

Thanks to the soltrack-2.2 library. This library is used to calculate the sun's position based on the date, time, and location. The library provides the azimuth and elevation angles of the sun, which are used to adjust the solar panel's position.