Arduino Solar Tracker (Single or Dual Axis)
If you’ve installed solar panels on a camper van to provide you with electricity on your camping trip or at home to supplement your electricity usage or take your home completely off grid then you probably know that the panels work the best when they are aligned directly towards the sun. This sounds simple enough, except that the sun moves throughout the day. This is why there are now a number of different mechanisms which work on a range of principles with the purpose of aligning your panel or array of panels directly towards the sun, they are called solar trackers.
There are two principle types of trackers, single and duel axis trackers. Single axis trackers are adjusted every month or so account for seasonal changes in the suns position, the single axis is then used to track the daily movement of the sun across the sky. Duel axis trackers eliminate the need for monthly adjustment by using one axis to track the suns daily movement and another axis to track the seasonal movement. A single axis solar tracker improves solar output by around 25% and a dual axis tracker by around 40% according to this article on Altestore.
This solar tracker control system is designed to take light measurements from the east and west (left and right) side of the solar panel and determine which way to move the panel to point it directly at the source of the light. A servo is used to actuate the panel tracker; these are available in a broad range of sizes and can be scaled according to your panel size. Although this tracker is single axis, the two sensors and servo can simply be duplicated to provide dual axis control.
This project assumes you know the basics of Arduino programming, otherwise read my article on getting started with Arduino.
You could also take this project further by building your own solar panel as well, here is our guide on how to build a solar panel at home. If you are thinking of switching some or all of your homes power requirements to solar power, read my article on switching to solar power first.
Update: I have had a number of requests to show how this project and code can be modified to drive a linear actuator for heavier loads and panel arrays. I have written up a “how to” on the physical changes required as well as the revised software to make a linear actuator driven solar tracker.
Step 1: What You Will Need for a Solar Tracker
Here is a list of the items which you need in order to complete this project. If you are looking to make a dual axis tracking stand then you will need to double up on the servos, LDRs and resistors.
- An Arduino (Uno used here) – Buy Here
- Single Axis Tracking Stand (Brief DIY Design Shown In Step 6)
- 2 x 4.7K Resistors – Buy Here
- 2 x LDRs – Buy Here
- PWM Servo – Buy Here
The specific servo model or size has not been stated as it depends on the size and weight of your solar panel. The one used in this project is a 9 gram analogue servo. You can use any size PWM hobby servo with the Arduino although the larger servos will require their own power source.
Step 2: Assemble the Components
First you need to start by assembling the components onto your solar panel, or breadboard. The LDRs (light dependent resistors) or PRs (photo-resistors) change resistance with changing light, therefore they need to be connected in such a way that the changing resistance is converted into a changing voltage signal which the Arduino understands. The servo is controlled through one of the Arduino’s PWM outputs.
If you are going to be installing the solar tracker permanently then you may want to solder the resistors and LDRs together so that they cannot come loose. If you are simply trying this project for fun then a breadboard is perfect.
The basic circuit for the connection of the LDRs and servo to the Arduino is shown in the attached image.
The resistors R1 and R2 are each 4.7K, the PR1 and PR2 are the two LDRs and the servo can be any PWM hobby servo. If you are using a servo larger than 9 grams then the Arduino will probably not be able to supply it enough power to achieve its full torque capability, you will need to supply the servo directly with its own 5V power source.
If you are making this a permanent installation, then it is best to solder the resistors right up near the LDRs on the panel. This way you can run a single 4 core wire from the control box up to the sensors on the panel, the four cores will be 5V, Gnd and then signal 1 and 2 from the LDRs. Once your LDRs and resistors have been soldered together, you can mount them on your solar panel. Mount the LDRs on the east and west (left and right) sides of the panel facing towards the sun. Make sure that they are not shaded in any way by the frame and have an unobstructed view of the sun.
A breadboard has been used in this project purely to distribute the Ardunio’s 5V power supply to both the resistors and the servo.
The servo needs to be sized according to the size of your solar panel. The panel used in this example is small and relatively light; a small servo was therefore used and is powered by the Arduino. For a larger servo (anything above 9 grams), you will need to power the servo externally as the Arduino doesn’t have sufficient capacity for it. Make sure that you connect the external power sources ground to the Arduinos GND as well otherwise the PWM control signal to the servo will not work.
Step 3: Upload the Sketch
Now you can upload your sketch onto your Arduino, if you haven’t uploaded a sketch before then follow this guide on getting started.
The sketch is shown in the attached image.
Here is the link to download the Solar Tracker code.
The code essential measures the light intensity from both photo resistors, it then compares the two to see which is receiving more light. If the difference is greater than a small threshold then the Arduino tells the servo to move in that direction to direct the panel towards the light source. If the light falls below a certain level on both sensors then it is detected as night time and the panel is moved to face east again for sunrise.
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