Solar Tracker system Using LM358

We all know that a Solar Panel can be used to convert light energy to electrical energy. The amount of converted energy depends on the amount of light falling on the Panel. Generally Solar Panels are stationary devices which is fixed at a position. The produced electrical energy can be increased if we move the solar panel as the movement of the Sun. Here is a simple low cost Solar Tracker circuit which automatically moves the solar panel in the direction of Sun. The movement of the Sun is detected using two LDRs which are arranged on the Solar Panel in such a way that the intensity of light falling on it varies as the direction of Sun changes.

Circuit Diagram

Simple Solar Tracker Circuit Diagram

Simple Solar Tracker Circuit Diagram


The heart of the above circuit is two voltage comparators made using LM358 Dual Op-Amp. We all know that when the intensity of light  falling on a LDR increases, its resistance decreases. Here LDR is connected with a series resistor (R3 & R4), hence when the intensity of light falling on a LDR increases, voltage across corresponding resistor (R3 or R4) increases.

The output of the voltage comparator will be high when the voltage at non-inverting terminal (+) is higher than the voltage at the inverting terminal (-). Inverting (-) terminals of both comparators are shorted and connected to a variable resistor (RV1), which is used to set the reference voltage. Thus the sensitivity of both LDRs can be adjusted by varying the 10K pot shown on the left side of the circuit diagram. When the light falls on a LDR increases, voltage at the non-inverting (+) terminal of corresponding comparator increases and its output goes HIGH.

Solar Tracker - Various Modes

Solar Tracker – Various Modes

The direction of motor rotation is controlled by the H-Bridge formed by the complimentary symmetry transistors BC547 and BC557. Consider the case when the output of first comparator (U1:A) is high and output of second comparator (U1:B) is low. In this case transistors Q1 and Q4 will turns on and the resulting current rotates the motor in clockwise direction. Consider the case when the output of the first comparator is low and the output of the second comparator is high. In this case transistors Q2 and Q3 will turns on and the resultant current rotates the motor in anticlockwise direction. If the output of both comparators are low, transistors Q3 and Q4 turns on, but no current will flow through the motor. Similarly if the output of both comparators are high, transistors Q1 and Q2 turns on, but no current will flow through the motor.

The DC Motor should be connected to the panel in such a way that, the rotation of motor rotates the panel in the direction of movement of  the Sun.

Abhay Bajpai

I M pursuing engineering from Kanpur....i have interest in electronics circuit designing...and so i want to share my little knowledge!!!!!! :-)

  • Darma

    Hi. Find this circuit while searching for a solar tracker on the net. Just assembled & tried it. Seems that the transistors burned out because the motor was drawing too much current. Can they be replaced by a higher amp transistor?

  • Ligo George

    Ya, sure… just replace 4 transistors depends on your current requirements..

  • Darma

    Ok thanks. Will mosfet do the job also?

  • Ligo George

    Yes you can use mosfet………. base resistor is not required while using mosfet.. consider the current consumption of motos while choosing mosfet..

  • darma

    ok thanks a lot.

  • ehsan

    Hi.can you tel me how i can turn back it to east next morning for solar panel uses?

  • Ligo George

    I think it will automatically turn back.. .according to the light falling on it..

  • Akhilesh Agrawal

    what is the Power rating of motor you used? also can you suggest some motor for 1- 1.5 kg solar panel ? also what changes has to be made in the circuit according to the power of motor please. Thanks in advance :)

  • Ligo George

    It should be calculated depending upon the torque required….
    You can change the driving transistors as per the current requirements..

  • Hasan Abu Zayyad

    if the LDR1 and LDR2 has not equal resistance at the same level of lighting – which is the case i just face when i bought the circuit elements – also the 10k & 10k hasen’t the same value exactly (+ 4% or -4%) , does that affect ?? if yes , how could we solve this problem ?

  • Ligo George

    Then you may use two reference 10K variable resistors.. for each comparators..

  • Hasan Abu Zayyad

    I try it also it does not work !! , when shading LDR 1 i have 9 volt as output the VCC i used is 11 volt , when shading the other LDR2 i have onle 2 volt !! what would be the problem ? i tried to reconstruct the circuit for + 10 times , !! please HELP

  • Hasan Abu Zayyad

    thank U ^_^

  • Ligo George

    It might be the problem of the IC…
    The output of the comparators will be +Vsat or -Vsat.. Which will be approximately equal to your Vcc..

  • Amirul

    hello sir..i use a 12V 1W solar panel as the source 9-12V as the schematic diagram says. the motor doesn’t move even tough the ldr have been stimulated with bright light at one side. the output voltage gain are very small, in millivolt. can i know what is the prolem??

  • xavier

    dear Ligo George , could u suggest the suitable transistors at Q1,Q2,Q3,Q4 for the power rating 12v 5A

  • Vachan PraJapati

    hey i made same circuit . brother it’s not working :/

  • Javier

    Hey don’t work!. I have everything like diagrams said