Solar Tracking System

By Sunil Kumar

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Generally, solar panels are stationary and do not follow the movement of the sun. Here is a solar tracker system that tracks the sun’s movement across the sky and tries to maintain the solar panel perpendicular to the sun’s rays, ensuring that the maximum amount of sunlight is incident on the panel throughout the day. The solar tracking system starts following the sun right from dawn, throughout the day till evening, and starts all over again from the dawn next day.

Solar tracking system circuit

Fig. 1: Circuit of solar tracking system
Fig. 1: Circuit of solar tracking system

Fig. 1 shows the circuit of the solar tracking system. The solar tracker comprises comparator IC LM339, H-bridge motor driver IC L293D (IC2) and a few discrete components. Light-dependent resistors LDR1 through LDR4 are used as sensors to detect the panel’s position relative to the sun. These provide the signal to motor driver IC2 to move the solar panel in the sun’s direction. LDR1 and LDR2 are fixed at the edges of the solar panel along the X axis, and connected to comparators A1 and A2, respectively. Presets VR1 and VR2 are set to get low comparator output at pins 2 and 1 of comparators A1 and A2, respectively, so as to stop motor M1 when the sun’s rays are perpendicular to the solar panel.

Circuit operation

When LDR2 receives more light than LDR1, it offers lower resistance than LDR1, providing a high input to comparators A1 and A2 at pins 4 and 7, respectively. As a result, output pin 1 of comparator A2 goes high to rotate motor M1 in one direction (say, anti-clockwise) and turn the solar panel.

When LDR1 receives more light than LDR2, it offers lower resistance than LDR2, giving a low input to comparators A1 and A2 at pins 4 and 7, respectively. As the voltage at pin 5 of comparator A1 is now higher than the voltage at its pin 4, its output pin 2 goes high. As a result, motor M1 rotates in the opposite direction (say, clock-wise) and the solar panel turns.

Fig. 2 Proposed assembly for the solar tracking system
Fig. 2 Proposed assembly for the solar tracking system
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Similarly, LDR3 and LDR4 track the sun along Y axis. Fig. 2 shows the proposed assembly for the solar tracking system.


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This article was first published on 12 August 2016 and was updated on 27 May 2019.

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27 COMMENTS

  1. what are vr1,vr2,vr3 and vr4?
    what are the significances of vr1 in the circuit?
    if we are using 9v battery and motor then do we need to change the value of the resistances?

    • They are variable resistors. VR1 is used to set the voltage at output pin2 of comparator (A1). You may use 9V battery as power supply but in that case the output level at each comparator output will be different. And also you need to recalibrate the resistances at the input of each comparator.

    • No. Look carefully, the input voltage goes thru a 10k resistor so the voltage at those pins will be less or around 7V. The supply voltage may go up to 36V but in this case, only 12V is supplied. This circuit is based on a DIP package and NOT the SO package. If you use SO package, change the pinouts to reflect with the datasheet.

  2. Dear Mr. Sunil Kumar.
    I have made your circuit. I have had many problems.
    The Moto 2 never worked.
    In the end, the best solution was to add another IC LM339 and repeat the components and configuration of pins 1 to 7 for Motor 1 in the second IC LM339.
    Please, you can verify the circuit. From already thank you very much.

  3. Worked well. But will the LDRs not get fried or bridge the power supply if they are fully illuminated equally under bright sunlight?

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