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    The solar panels are operating at optimal parameters when they are at the perfect right angle to the sun. Unfortunately this is accomplished only if solar panels are rotated by the sun. This is the purpose of this diy solar tracker system or if you have an Arduino board then you can build this one that uses a servo.

    The solar tracker circuit uses a window comparator to maintain the motor in a idle state as long as the two LDRs are under the same illumination level. In this case, half the voltage is applied to the noninverting input of A1 and to the inverting input of A1.

    Solar Tracker Circuit Schematic

    solar tracker circuit schematic

    simple diy solar tracker system schematic

    solar tracking components

    • T1, T3 = BD239, BD139
    • T2, T4 = BD240, BD140
    • A1, A2 = 1/2 of LM324
    • Diodes = 1N4001

    When the sun position is changing so does the illumination level on the LDRs and the input voltage for the window comparator is no longer half of the supply voltage thereby the output of the comparator generates informations for the motor that rotates the panels for tracking the sun.

    diy sun tracking sensor

    diy solar tracker sensor

    diy sun tracking sensor

    P1 and P2 are adjusted in such way that the motor stands still when the LDRs get the same amount of solar light. If less light reaches LDR2 than LDR1, the voltage in point A increases to more than half of the power supply voltage. As a result the output of A1 is HIGH and T1 and T4 transistors conduct. In this situation the motor is starting.

    If the angle of the solar light is changing again and the voltage in point A decreases at less than power supply voltage, the output of A2 goes HIGH and T3 and T2 transistors conduct. As a result the motor is rotating in opposite direction.

    For solar panels control is best to use small motors with a suitable voltage and a maximum working current of 300 mA. This solar tracker system is used for tracking the sun only in one plane, the horizontal one. If you want to track the solar light in the vertical plane you need to build a separate sun tracker circuit.

    Analog Solar Panel Tracker Circuit by Bien Fallaria

    analog solar tracker

    analog solar tracker circuit schematic by Bien

    This is a simple and practical analog solar panel tracker circuit. Using four LDR (light dependent resistor) as a sensor in detecting the light source arranged as illustrated. When the light hit the LDR in a certain position, it will activate the circuit and trigger the relay to turn the slewing motor in the right direction until the sensor is fully shaded under its cover stopping the motor to its rest condition.

    ask a question

    36 Responses to "DIY Solar Tracker System"

    1. For the vertical plane can I use the other 2 amplifiers inside LM324? I see you are using 2 of them and as I know the IC has 4.

    2. :) I really like this circuit, it is so simple yet can help a lot in harvesting the free solar energy!

    3. sure this circuit is so simple, but can i replace the resistor 15k and 47k so that it can be use as the gate controller or use it as door opener? thanks

    4. It’s a great circuit.
      I just have one question.
      Doesn’t it have to be reset in the evening ?
      What I mean is :
      is LDR1 set in such a position to the east that it will turn the solar panel back in the morning ?

      THX T L.

      • Actually it doesn’t go back to its original position automatically. But it will track back the sun in the morning. The most important thing is the design of the tracking sensor.

      • Of course Marian.
        The design is simple and nifty.
        I’ve been looking and digging around,
        and the gain is about 15 – 20% with this design integrated.

    5. Could 3 ldr’s make it so it resets to the east as soon as the “east” ldr revives light ?

      And could you amend the circuit to show 3

    6. What motor do you use ?
      Can i use 12 volts motor ?

    7. I am an electrical engineer and I like making electronic circuits . I will surely make this circuit as my mini project.
      Thx alot for the circuit sir

    8. what is the cost of this project?

    9. I think the circuit should add a hysterisis of a few millivolts to both the comparators as in a practical situation, the output might tend to oscillate at the point of equality which may even harm the motor.
      correct me if i am wrong :) .

    10. can we reset the motors position by using any controller ic for every 24 hrs

    11. http://www.youtube.com/watch?v=Sf4jJXVRux8

      Hi above link for perfect device tracking sys.

    12. its really simple cicuit.sir i have one more doubt..where will i connect solar panel??

    13. Sir as per your schematic diagram i assemble the circuit i was worked some time as LDR not responding very effectively. After some time when testing towards sun direction it shut down i dont get where is the problem. Can you give some guidance?

    14. Which motor is used ?
      A stepper motor or ordinary?

    15. mistry kushal says: on April 5, 2014 at 3:51 pm

      how many voltages motor used in this cicuit.
      reply me fast..

    16. Hysteresis would be a very good addition to this plan. Use a 4.7 m or higher pot so it can be tuned for feed back sensitivity. Also you could replace the Q’s with FET’s but the G terminal will need 2 voltage dropping R’s from outputs to G to grnd. so the Gate is not over driven , it will add some components but the difference between the gain of the Q’s with their resistance compared to the FET’s is much more effective at driving the servo -AKA Linear Actuators, these are the Spend-ee parts. As far as using the other 2 comps., this is another great idea. The other 2 will track seasonal changes which obviously will be very unnoticeable from day to day, but does make the system more productive. This will also give the system a tilt to south for keeping the snow clear in the winter and take the panels out of a direct hail shot if you are using the Micro P. . Here is the biggest problem with this type of system. Solar panels are as everyone know covered with glass, so if they take a hit from a large piece of hail they are toast. It takes a lot but it does happen. The best way to build a solar tracking device is with a Micro P. and use the same basic circuit here, the H Bridge, the sensor circuit, but the code is the tough part. You want the code to include a portion that will take the panels to a neutral point if the ambient light falls below a certain level, as if on a cloudy day or night time. By having this, the panels and sensor will be closer to the new day light. With a micro P. hysteresis is written into the code so that is critical to get stable, otherwise the system does the Hoochy Koochy dance and it that is ‘BAD’! Like someone with a terrible case of Parkinsons. The diodes used across the E and C of the Q’s or the S-D of the FET’s MUST be a higher PRV then the 1n4001’s though,TVS’s are even better since DC motors cause V spikes in both polarities. Use a TVS of a V rating above the DCV but below the Max of the Q’s.( these little 1n4001 diodes are fine for bench testing for design but will only cause you grief in the finished system ) especially if you are using a larger more powerful series wound drive motor ! I would always go to OVERKILL on these! Like a 1 watt or even a 5 watt @ 400v or more on the diodes, the TVS’s are another deal. There is nothing wrong with doing this but a blown diode and transistor will really kill your day. Spend a little more here or spend more there during the rebuild. I have a worked out circuit for the Micro P and a start on the code but I am not a code type guy so I am looking for someone that is into this that can finish that part and I also have an array that I am needing to test this on.

    17. Having a hard time finding those specific transistors, can you suggest more available ones?
      This is a very elegant circuit!



    18. hi, i’m a total newbie but setting up a small power unit at my bush camper and making as much as i can from scratch and learning but what i’m wondering is i’m going to be making some pcb’s for a bedini generator i’m making and was wondering if you had a pcb layout diagram to make my own boards when i make these ones i have sitting here,

    19. Good circuit. two questions though: what is the angle of incline between the two LDR’s and what is the length of the tubes and their diameters?,

    20. Daniel Villanueva says: on January 10, 2015 at 12:17 am


      I don’t have yet any comment/s
      at this time, but I want it to know if you have a latest designed
      Of this automatic sun tracker that
      Suitable for solar panel up to 2 Kwatts??

      Thank you for your reply!


    21. where do i get this ldr circuit plzzz tell i want to do this project

    22. can i use this in paraboidal dish of my project

    23. i need dual axis solar tracker for parabolic & Fresnel glass

      Sudhir Ramani
      +91 9377205500

    24. Do we have a model number for the LDR’s?

    25. hello Sir,
      I have 6 solar panels each 150W , and want to place it on tracking system ….your system is awsome but the problem is ….which servo motor is used to rotate these 6 panels
      motor power=?
      motor torq=?

    26. Abdullateef Ali says: on August 17, 2015 at 11:34 pm

      Thank you very much.
      It’s very good circuit, but I have one question.
      What type of LRD’s can we use in this circuit and the size.
      Thank again.

    27. if i want to reduce the size of this project then which components that i have to use ?

    28. Thank you very much.
      It’s very good circuit, but I have one question.
      What type of LRD’s can we use in this circuit and the size.
      Thank again.

    29. ju]liu]]]]]]]]s says: on October 16, 2015 at 8:11 am

      do yo think that i can also manage to build one and using the same method leave it to manual and succeed?

    30. This circuit is working as expected as long as you keep the wires from the power supply short ( under 1 meter ). If they’re longer, then the voltage drop accross those wires will be significat enough and you won’t have enough power to drive the actuator..
      The quick fix is to add a voltage regulator at the circuit’s end to overcome the drop.

      I had 3-4 meter wires from the power supply to the tracker and encountered this problem.

      Everything started working once I added a 12V voltage regulator to power the tracker.


    31. alenibryahoo-com says: on May 16, 2016 at 3:33 pm

      Can i replace the239 with139& 240 with140?

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