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Simple Solar Tracker System – Mechanism and Control Circuit Explained

The circuit and the mechanism explained in this article may
be considered as the easiest and perfect dual axis solar tracker system.

The device
is able to track the daytime motion of the sun precisely and shift in the
vertical axis accordingly.
 The device also effectively tracks the seasonal
displacement of the sun and moves the entire mechanism in the horizontal plane
or in a lateral motion such that the orientation of the solar panel is always
kept in a straight axis to the sun so that it complements the vertical actions
of the tracker appropriately.

solar tracker mechanism with gears and dimensions
As shown in the figure, a relatively easy mechanism can be
witnessed here. The solar tracker is basically mounted over a couple of stand
with a central movable axis.
The pivotal arrangement allows the panel mounts to move on a
circular axis over almost 360 degrees.
A motor gear mechanism as shown in the diagram is fitted
just at the corner of the pivotal axis in such a way that when the motor
rotates the entire solar panel shifts proportionately about its central pivot,
either anticlockwise or clockwise, depending upon the motion of the motor which
in turn depends on the position of the sun.
The position of the LDRs are critical here and the set
of LDR which corresponds to this vertical plane movement is so positioned that
it senses the sun light accurately and tries to keep the panel perpendicular to
the sun rays by moving the motor in the appropriate direction through a
definite number of stepped rotations.
The LDR sensing is actually accurately received and
interpreted by an electronic circuit which commands the motor for the above
explained actions.
Another mechanism which is quite similar to the above
vertical setting, but moves the panel through a lateral motion or rather it
moves the whole solar panel mount in circular motion over the horizontal plane.
This motion takes place in response to the position of the
sun during the seasonal changes, therefore in contrast to the vertical movements;
this operation is very gradual and cannot be experienced on a daily basis.
Again the above motion is in response to the command given
to the motor by the electronic circuit which operates in response to the sensing
done by the LDRs.
For the above procedure a different set of LDRs are used and
are mounted horizontally over the panel, at a specific position as shown in the
diagram.
How the Solar Tracker Control Circuit Functions
A careful investigation of the circuit shown in the diagram
reveals that the whole configuration is actually very simple and
straightforward. Here a single IC 324 is utilized and only two of its op amps
are employed for the required operations.

dual axis solar tracker LDR circuit
The op amps are primarily wired to form a kind of window
comparator, responsible for activating their outputs whenever their inputs
waver or drift out of the predetermined window, set by the relevant pots.
Two LDRs are connected to the inputs of the opamps for
sensing the light levels.
As long as as the lights over the two LDRs are uniform, the
outputs of the opamp remain deactivated.
However the moment one of the LDRs senses a different
magnitude of light over it (which may happen due to the changing position of
the sun) the balance over the input of the opamp shift toward one direction,
immediately making the relevant opamps output go high.
This high output instantly activates the full bridge
transistor network, which in turn rotates the connected motor in a set
direction, such that the panel rotates and adjusts its alignment with the sun
rays until uniform amount of light is restored over the relevant set of LDRs.
Once the light level over the relevant LDR sets is restored,
the opamps again become dormant and switch off their outputs and also the
motor.
The above sequence keeps on happening for the whole day, in
steps, as the sun alters its position and the above mechanism keeps shifting in
accordance to the suns position.
It should be noted that two sets of the above explained
circuit assemblies will be required for controlling the dual actions or simply
to make the above discussed dual tracker solar system mechanism.

Parts List

R3 = 15K,
R4 = 39K,
P1 = 100K,
P2 = 22K,
LDR = Normal type with a resistance of around 10 K to 40K in daylight under shade and infinite resistance in complete darkness.
Op-amps are from IC 324 or separately two 741 ICs may also be incorporated.
T1, T3 = TIP31C,
T2,T4 = TIP32C,
All diodes are 1N4007
Motor = As per the load and size of the solar panel

Courtesy – Elector Electroniks India

How to Add a Set/Reset Facility in the Above Circuit

At the first glance it might appear that the above circuit does not incorporate an automatic resetting feature. However a closer investigation will show that actually this circuit will reset automatically when dawn sets in or in the morning daylight.

This might be true due to the fact that the LDRs are positioned inside enclosures which are specfiially designed in a “V” shape for facilitating this action.

From the reflection of of the rising sun light, during morning hours the sky gets more illuminated than the ground. Since the LDRs are positioned in “V” manner, the LDR which faces more toward the sky receives more light than the LDR which faces toward the ground. This situation activates the motor in the opposite direction, such that it forces the panel to revert in the early morning hours.

As the panel reverts towards the east, the relevant LDR begins getting exposed to even more ambient light from the rising sunlight, this pushes the panel even harder toward the east until both LDR are almost proportionately exposed toward the east rising sunlight, this completely resets the panel so that the process begins all over again.

solar tracker mechanism details with LDR installation and gear fitting

Set Reset Function


In case a set reset feature becomes imperative, the following design may be incorporated.

The set switch is placed at the “sun-set” end of the tracker, such that it gets depressed when the panel finishes it’s days tracking.

As can be seen in the below given figure, the supply to the tracker circuit is been given from the N/C points of the DPDT relay, it means when the ‘SET” switch is pushed, the relay activates and disconnects the supply to the circuit so that the entire circuit shown in the above article now gets disconnected and does not interfere.

At the same time, the motor receives the reversing voltage via the N/O contacts so that it can initiate the reversing process of the panel to its original position.

Once the panel finishes its reversing process toward the “sun-rise” end, it pushes the reset switch  placed suitably somewhere at that end, this action deactivates the relay again resetting the entire system for the next cycle.


129 Comments

  1. This circuit would result in dramatic and chaotic movement if any sort of shadow passed over one of the light sensors. If a leaf or bird dropping covered one the panel would spin constantly.
    Clearly this has never been actually used.

  2. Excellant circuit-appreciated the info on LDR's – i use very large one inch surplus LDR's in the bottom of a small tomato cans painted on the inside walls with green fingernail polish covered with plastic cover from flashlight and both cans taped together and mounted. Eazy to adjust and no problem with airplanes flying over my house to land at airport

  3. Sir we want to use this circuit as a part of our Final Year Project … We are using 100 Watts Solar Panel and Geared Motors … We have tried this circuit but this is not working by indenting Light on LDRs … Kindly can you help us in TroubleShooting … ???

    • Sir You are using same IC 324 But the Outputs which are provided to the H-Bridge are measured using Multimeter. It gives NOTHING (Zero Volts) … And Our Geared Motor is of About 2A (12V) rating. Will this circuit will work for this Motor as Well ???

    • hi, i have try this its working but a bit problem it runs only tape recorder motor, i want to run gare motor but i think there is a problem of current i have use bc 547,557 instead of tips what to do now?? regards

  4. kindly explain the role of t1 t2 t3 t4…
    i got the point of using the op-amp here…its output too….but what after that????? why are we using the transistors and y this fashion of arrangement with the motor????

    • with balanced light on the LDRs, both the opamp outputs are logic 0 keeping the PNP transistors switched ON, and NPNs switced OFF.

      supposing LDR1 gets more light, pin#1 becomes high switching OFF T2 and switching ON T1, since T4 is already ON (because pin#7 is low) current passes via T1, motor and T4, allowing the motor to rotate on one of the directions.

      The opposite happen when the lower LDR gets more light……

      I hope you got it.

  5. Can we Use Geared Motors Rated 2A 12V here in this circuit for a Dual Axis Tracker … Total Load for One Motor will be Approx (15-20)KG For the One Axis Horizontal Rotation and The Load for the Other Motor will be Much Lager because we are using it at the Base for the Horizontal Rotation … ???
    Can you guide in this regard?

  6. Sir can you Explain the working of OP-Amps here in this circuit specifically. I mean how these OP-Amps will work according to the changing output voltage of LDRs when illuminated ???

    • Ok Thanks a Lot Sir … Sir currently we are facing with the Tracker circuit … We have tried the above circuit … At present the situation is that Motor is Rotating Continuously in in ONE direction by illuminating either LDR … And when we cover both the LDRs (i.e. No Light) the Motor stops. But the main problem is that Once the motor starts rotating, it rotates continuously in ONE Direction irrespective of the LDR Illuminated. Can you help us Why is it So?

    • Illuminate the LDRs with same amount of light, and adjust the presets such that the output of the opamps produce zero voltage.

      After this if any of the LDRs is subjected to a different intensity light, the relevant opamp would produce a high at its output.

      This is how it needs to be adjusted.

      Angling the LDRs is also critical, do it as indicated in the tracker image.

  7. Sir I have a little bit of confusion … Kindly guide us in this regard.

    1. Suppose that this circuit tracks the position of Sun during the whole day and in the Evening when the Sun sets, this tracker will be directing towards West position. Now, is this circuit capable of Automatically going back towards East Position because in the Next day, the Sun will rise from the East … ???

    2. Can we replace the TIP Transistors with MOSFETs in order to use the dc Motor with high current Ratings … ??? If so then How … ???

    Kindly Explain these two Questions Separately and THANK YOU for your continueous responce, we find it very much helpful.

    • 1) this circuit does not have an automatic resetting facility, you would have to do it manually every morning or at night.

      2)No, you cannot replace the transistors with mosfets. You may use tip36/tip35 for getting high current.

  8. And If we want this circuit to Perform the Resetting Automatically as well by not changing this original circuit, what additions we have to do with it ??? Actually we want this circuit to Reset as well … Kindly assist us if you have any idea regarding this?

  9. Please tell us that in Set/Reset circuit given in the link listed in the above mentioned Reference, where the Switches will be placed? And theses Switches will be Limit Switches or any other? And will the same Motor will work for this purpose as well or a new Motor will have to be connected?

    • yes you may use a limit switch or any form of sturdy push-to-ON switch.

      the swiches should be fixed on some raised platforms on both sides, over which the panel would touch down and rest at 45degree angle facing either of the sides.

      the two switches should be positioned on these platforms such that when the panel rests over them, the relevant switch gets pressed.

      yes the same motor would work.

      find out which opamp output generates the reverse rotation in the motor, and do the following modifications:

      disconnect this opamp output and connect it through a 1N4007 diode to the bridge transistor base, also connect a 1K resistor from the transistor base side to ground.

      Now connect the collector of the set/reset PNP transistor with the above bridge transistor base through a diode 1N4007. the relay is not required remove it.

      Now the motor will move in the opposite direction everytime the reset button gets depressed by the panel at dusk.

    • be sure to connect collector of the PNP transistor to the bridge transistor base via a 1K resistor……otherwise the bridge transistor will blow of.

    • Dear Prashant, I think you are trying to say that the circuit trips automatically to external electrical disturbances….

      You can solve this by adding a 1uF/25V capacitors across the S2 terminals

  10. Where the switches connection will be made in the circuit? Kindly upload the Final Circuit Diagram with these Set/Reset Switches connected as well along with the required modifications you mentioned above.
    Thanks a lot in Advance!!!

  11. Sir, Should we use the Power of 12V Directly from the Battery, our main Storage Bank for this Whole system or We design any Power Supply Circuit separate to Power this Tracker circuit? We are using Geared Motor of Approx. 2A … So Kindly tell us what to do in this Regard?

  12. Sir Kindly update the Above given Electronics circuit with the SET/RESET Connections as well … I mean Where the Switches will be connected Electrically???

  13. Sir We want to incorporate the Relay and Push Buttons to perform this SET/RESET Operation. Kindly help us in Wiring the Relay Contacts for doing So depending upon the Set/Reset Button. Thanks

    • In the above circuit, external set reset arrangement will not work because the LDR response will interfere with the external actions.

      The LDR response will automatically revert the panel during sun rise.

  14. Hi Swagatam

    A little suggestion. Rather putting a Push to On switch in Set/Reset option one should go for a REED switch. Small magnet pieces may be pasted on moving Panel sides and reed switches may be fixed on static portion on some raised platform accordingly. Reed switches being encapsulated in a Glass tube will go along well with extreme weather condition and also is water proof. A plus point is that its contact will remain clean however it should never be used for higher currents as spark inside it will damage it and resulting it useless.

    Regards

    Sam

    • Hi Sam,

      Thanks! That's a wonderful idea and could be tried, however in the above design the inclusion of switches won't work for resetting the panel, simply because the LDR sensing would interfere with the switch operations, and that's why I had to cancel the idea of mechanical switching for the purpose.

  15. AOA

    A white LED can be installed near LDR appropriately which may stay off in normal operation. Above mentioned reed switch should only turn on that white LED for a mere 30 second and it will do its magic simply, like old days. What do you say?

    Regards

    Sam

  16. AOA

    Another idea is also popping in my mind. A cheap alarm clock may be installed inside circuit box and alarm can be set at 07:00 AM. Alarm output can be detected to activate another circuit (or above mentioned LED) to move panel appropriately. I haven't read all comments but I think that's what you may trying to achieve.

    Regards

    Sam

    • Hi Sam,

      Interesting ideas!

      However I am expecting the LDRs to do it by themselves during every morning….until tested it cannot be confirmed, though.

  17. Sir we have checked this circuit by Placing the LDRs in the "V" Arrangement but it donot works fine for RESET/SET. Kindly update this circuit with the SET/RESET External circuitry without changing the Basic Circuit because it works fine for the Tracking purpose but the it just lacks the SET/RESET Functionality. We need the SET/RESET functionality as well. Kindly update this circuit as soon as possible.
    Thanks in Advance!!!

  18. Sir we have Tried this SET/RESET circuitry … We have merged these Above two circuits Together on a Single PCB … Now The Response of the Circuit is that when SET button is pressed, The MOTOR's Direction is not changed But It continueously keeps on Moving in the same direction (ClockWise/AntiCLockwise) as it was initially without Presseing the SEt Button. On the other Hand when RESET button is pressed, The Motor gets Stopped.
    Kindly can you Guide us where the Problem might be … ???

    Thanks a Lot.

  19. Sir there is No Effect on the Circuit's Working in Reversing the Motor's Connections as Well, It z working Same as described in the Previous Comment.

    • that's impossible, a DC motor rotation direction will instantly change when its wire polarity is chnaged, there may be some other issue with your circuit.

  20. I have idea about reversing the panels. if we connect the relay supply form panels wires. in day time the relay will on and supply current to circuit and during night when panels stop supplying current the relay will Off and supply current to the motor so the panels will reverse..

  21. PLS CAN I USE THE SET/RESET CKT TO CONTROL AN AUTOMATED GATE MOTOR(S), SO THAT WHEN THE MOTOR ROTATES TO OPEN THE GATE IT TRIGGERS OFF, AND THE OPPOSITE DIRECTION (WHEN THE GATE IS CLOSED) THE CKT TRIGGER OFF AUTOMATICALLY, AND HOW IS CONFIGURED……….. PLS SIR SWAGATAM, I WOULD LIKE TO ADD THAT TO MY FINAL YEAR PROJECT WORK, OR IF THERE IS A CKT THAT OPERATES THAT WAY…..THANKS, WAITING FOR YOUR RESPOND.

  22. I understood the concept of tracker circuit,
    can you explain the concept of set/reset circuit?
    does the 12v supply to tracker circuit is related to rating of the motor?

  23. actually i also assemble one circuit like this but part are different i use BD 239 BD 240 & BD 139 BD 140 at T1 T2 parts & IC LM 324. It is also same but when it start to track i adjust pot resistor but here some difference as one ldr get more light then motor moves slowly. ldr not giving balance resistance at same amount of light. I tried both small & medium LDR but both not working giving better result as excepetd so can circuit work better than my circuit. because im not electronic engg for reading the circuit. Caqn you give me suggetions & guidance. please reply.

    • you will have to set the presets by exposing the LDRs to same amount of artificial light.

      the above setting should be tried until the motor completely shuts off or shows no response. Once this is set and confirmed, you can use it for the actual sun tracking implementation.

  24. there are two motors to be used one for east-west and other for north-south,the same circuit is used for two motors.i am not getting clarity about the above circuit is used for one motor functioning or both plz explain me

  25. Do you have any light sensor circuit for set reset operation because at sunset illumination is absent and morning sunlight will be present so if we use sensor for set reset can there be any circuit be designed

    • Thanks,
      I meant to ask about the design and working of the circuit.
      In case of op-amp 1, pin 2 is connected to 12v with the voltage divider setup consisting of resistors 13K,100K & 22K,by voltage divider method voltage at pin 2 is
      = 12*(115/115+22)=10v is reference voltage. and op-amp 2 with reference voltage 4.3v
      when LDR is in dark setting resistance is 12K.
      When light falls on LDR which op-amp gets activated and how?

    • you will have to learn how an opamp functions as a comparator for understanding the above circuit.
      Briefly when the (+) inputs are high with respect to the (-) input the output of that particular opamp will be high and vice versa.
      LDR in light will increase the voltage level across the relevant pin of the relevant opamp and when in dark will do the opposite with respect to the other pinouts reference voltages.

  26. I am not getting the connection to 12v 8 pin relay. In the circuit 'to the circuit' means where to connect. I am usig KT 450 relay it has pins 1 4 6 8 9 11 13 16. Pins 1 16 coil 4 14 com 6 11 N/O 8 9 N/C. Guide me how these tins are connected in 2nd circuit please

    • it means to the circuit supply rails (+) and (-)
      you will have to find it by yourself with the help of a meter. find the common pole, the N/C and N/O contacts by trial and error or by referring to some relevant online relay diagram.
      N/C will show continuity with the pole when power is not applied to coil, and N/O will connect when the coil is powered up.

  27. Worked a lot on set/reset circuit but not working. I checked the base current of t1 when set is on and even off there is no difference showing 0mA. What to do ?
    Are the resistors values to be changed?

  28. My set reset circuit is working. I checked by connecting red and green leds at N/C and N/O positions its working perfectly but when I connected a 12v motor it is not working.
    When set is touched motor rotates one direction when reset is pressed the motor should rotate in opposite direction even reset switch is released but this is not happening when I released the reset switch direction is same as initial. It should rotate in reverse till again set is pressed actually.
    Should I have to change the transistors with high current ratings

    • In the last circuit given in the above article, the motor will rotate only when the set button is pressed…the relay is not wired to rotate the motor in the opposite direction because we need only to set the panel back to its original position in one direction only, so the motor does not need to rotate on both directions.

      When the set button is pressed and while the motor is rotating, the relay N/C contacts makes sure that the tracker circuit is switched OFF from receiving voltage and thus does not react in any manner while the above is taking place.

  29. Dear Swagatam:
    Many thanks for the circuit.
    I built the circuit and have noticed the following.
    (a) A possibility exists that both outputs are switched ON. How can we avoid this?
    (b) When powering down, the motor rotates in one direction for a small amount of time and then stops. What could be the reason ?

    Please comment.

    • Dear M&D,

      both outputs ON is very unlikely, you might be witnessing a leakage voltage issue across both the opamp outputs during the transitions, even that's not possible because the switching thresholds of the two opamps are assumed to be set wide apart.

      Connect a 3V zener and a LED in series with the output terminals of the opamps… this would possible solve all the encountered issues.

      The LEDs would also provide the relevant indications.

    • sorry, I do not have the picture of the finished prototype, the idea was taken from an old elektor electronics magazine.

      you can isolate the H bridge section and check it separately using manually triggered signals across the transistor bases in order to simulate and troubleshoot the fault….

    • the opamps detect the sun light balance on the two LDRs and accordingly command the H bridge to switch the motors and restore the panel position until the light balance on the LDRs become equal.

      it's impossible to use use LDRs directly with the Hbridge for getting the same results…not sure how you did it.

  30. hey @Swagatam could you please give me an estimate of total cost of this sytsem in INR as i am making a solar inverter for my final year project and wish to incorporate this with my solar panel…

    • Hi Soumitra, I have no idea about it since the design is mostly mechanical and the solar panel cost can vary a lot according to its specs…
      also note that this project can be extremely tough for a novice so think twice before you decide on going ahead with it

  31. Greetings!

    I built your circuit and works fine. However, I get "unbalanced" results sometimes. Can you tell me how to adjust "P1" and "P2" trimpots properly?

    Thanks in advance and Mabuhay from the Philippines!

  32. Hi friend

    I made this circuit, it is working beautifully and the set/reset switch also working great but only problem is when the sunset limit switch activated it goes reverse and stop but again searching light intensity rotating up and down continually so I have to stop the circuit supply manually. In the night 🌃 time no light condition but this motor works only one direction and stuck then the transistors start to get hot and some times blown up. So my dear friend please help me to overcome this problem.
    At night time condition is both LDRs resistance is very high and no center voltage, both presets are not respond motor goes only one direction.

    • Thanks Ranjith, you can rectify the problem by adding an additional relay driver stage whose relay stays activated as long as the sun light is just sufficient for the tracker to operate….as soon as the sunsets or the light become too low, the relay of this driver stage switches OFF, and in cuts off the battery supply to the motor

  33. @Swagatam, In the SET / RESET circuit you have shown, the power to the tracking circuit is disconnected when the SET switch is activated. How can the LDR's work at that point of time with no power applied to the circuit ? Please elaborate.

    • M&D, the LDR circuit is deactivated when the "set" button is pressed by the panel, but as soon as the panel restores itself back in the original position the "reset" button is yet again "pressed" by the panel which reverts the relay contacts back to the "circuit" position enabling the circuit with the supply voltage

    • Hi Brian, adding hysteresis could stop the panel from adjusting to the best optimized positions, which in turn could cause inefficient charging or inefficient solar consumption…so both ways it would be the same…

      I have not yet investigated the IC 555 option, it might be possible.

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