Solar Tracking SystemSUNIL KUMAR

Generally, solar panels are stationary and do not follow the movement of the sun. Here is a solar tracker system that tracks the suns movement across the sky and tries to maintain the solar panel perpendicular to the suns rays, ensuring that the maximum amount of sunlight is incident on the panel throughout the day. The solar tracker starts following the sun right from dawn, throughout the day till evening, and starts all over again from the dawn next day. 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 panels position relative to the sun. These provide the signal to motor driver IC2 to move the solar panel in the suns 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 suns rays are perpendicular to the solar panel.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.

How to Build a Dual Axis Solar Tracker System - Mechanism and Control Circuit ExplainedPosted byhitmanThe circuit and the mechanism explained in this article may be considered as the easiest and perfect dual axis solartrackersystem. 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 thesolar panelis always kept in a straight axis to the sun so that it complements the vertical actions of thetrackerappropriately.

As shown in the figure, a relatively easy mechanism can be witnessed here. The solartrackeris basically mounted over a couple of stand with a central movable axis. The pivotalarrangementallows the panel mounts to move on acircularaxis 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 whenthe motorrotates the entiresolar panelshifts proportionately about its central pivot, either anticlockwise or clockwise, depending upon the motion ofthe motorwhich 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 movingthe motorin the appropriate direction through a definite number of stepped rotations. The LDR sensing is actually accurately received and interpreted by an electronic circuit which commandsthe motorfor 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 wholesolar panelmount incircularmotion 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 tothe motorby 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 SolarTrackerControl Circuit FunctionsA 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. 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 alsothe 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 dualtrackersolar 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-ampsare from IC 324 or separately two 741 ICs may also be incorporated.T1, T3 = TIP31C,T2,T4 = TIP32C,All diodes are 1N4007Motor = As per the load and size of thesolar 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 whendawn setsin or in themorningdaylight. This might be true due to the fact that the LDRs are positioned inside enclosures which arespecfiiallydesigned 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 activatesthe motorin 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.

Fig. 1: Circuit of solar tracking system

Set Reset Function

In case a set reset feature becomes imperative, thefollowingdesign may be incorporated.

The set switch is placed at the "sun-set" end of thetracker, 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 thetrackercircuit 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 motorreceives 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 actiondeactivatesthe relay again resetting the entire system for the next cycle.

A DC motor controller have many form, which is difficulty easy to differently. Today, suggest building a simple two way DC motor control circuit.It is a H-Bridge that many popular and have high performance.That H-Bridge circuit, we will see that are most control circuit to moving of a robot.We can design the circuit with mosfet or transistor to control rotating of motor. Which I suggest example them as switch, so easy to understand by see its working as Figure 1.

Figure 1 All the switches are off cause motor not rotate.In circuit we see that is the open switch state, no current flowing in circuit cause the dc motor cant work.As Figure 2 When have the S1-switch (close) and S3 (close), cause that motor is derived the current, as we notice that current flowing in to the positive terminal of motor, making the dc motor rotated in features of forward form Or rotate clockwise.

Figure 2 the switch-S1 and S3 are close cause motor rotates.

Figure 3 the switch-S2 and S4 are close cause motor rotates back counter clockwise direction.And If S4 and S2 close together, Motor also get current that flow through them, but will dont same first form. Because that current will flow through the negative of motor cause current reversed or Rotated back counter clockwise direction. As Figure 3Start to apply transistorsWe will try to use all the transistor as switch. You see in figure 4 . When base is derived current electricity cause transistor running and motor will rotated.

Figure 4 Using the transistor as switches.

Figure 5 we use the four transistors as switch controller.As Figure 5 we try to take the four to connected into the H-bridge circuit. By we insert a diode to protect the electricity that may flow backward from the motor cause can be damaged the transistor.

Figure 6 apply power into A-point,Q1 and Q3 works,motor rotate forward directions.In Figure 6 circuit if we apply power to A-point. We will makes Q1 and Q3-transistor works because that get IB-current into base. So, the motor will rotated on forward direction, because that electrical current flowing from Q1 into the positive of motor, and flow through Q3 to ground successfully.

Figure 7 Apply B-pointThen later as Figure 7 we change power supply point into B-point. The Q4, and Q2 also works by they get current from base makes them have current flow through Q4 go to the negative of motor and through Q2-transistors to ground. But flowing of current in this form cause the motor rotated forward there.You can see real application the H-bridge circuit hereThe 2 channel DC motor driver on