Circuit Description of the Controller Circuit
The points below will clearly explain how the proposed electronic solar tracker controller circuit works:
- Referring to the circuit diagram (click to enlarge) we see that the entire circuit is built around the gates N1-N4 of IC 4093 (Quadruple 2 Input NAND Gate, Schmitt Trigger).
- N1, N2, and N3 are all wired to form a window comparator. It monitors the voltage at point “A" and keeps it within a particular range set by P1 and P2.
- The voltage at point “A" will vary only when the light intensity falling on the two LDRs are not equal, i.e. when the sun rays are not perpendicular to the solar panel’s surface.
- Assume that the light falling over LDR1 reduces its resistance sufficiently and crosses the higher reference level set by P1.
- Point “A" becomes high enough to trigger N1 whose output instantly goes low turning ON the driver transistors T1, T3 through N2. The motor M1 connected to the transistors activates and adjusts the solar panel so that it faces the sun rays at 90 degrees. The LDRs now also receive equal light intensities, point “A" potential returns back to the set window level and the motor deactivates.
- Now suppose the whole set up is positioned the other way round, i.e. opposite to the position which may produce the above explained situation.
- Here, as the sun drifts, at some instance the light falling over LDR2 will cross the lower reference level set by P2. The level at point “A" will fall enough to make the input of N3 go low. Its output will invert to activate transistors T2, T4 and the motor. The motor rotates, but now in the opposite direction to correct the tilt of the solar panel until everything is back to normal.
The above two operations will enable the system to track the sun over a single plane only i.e. on the vertical plane.
To make the system track the sun laterally, another set of the above described solar controller circuit will have to be employed.
The circuit operation will be exactly similar to the above explanation. But in this case the second motor M2, fixed over the wooden base will be activated and will correct the position of the solar panel over the horizontal plane or laterally. This operation will be very gradual and slow and a substantial shift can be identified over many months of time.
From sunrise to sunset the system will faithfully track the sun until it becomes dark. But, darkness would also mean the LDRs are subjected to equal levels of light, and the tracker would get stranded in that position until the next morning. But even after the sun rises the next day, the system will be totally unable to sense the light as it would be facing in the opposite direction then. The problem is solved by introducing switches S1 and S2 and is explained as follows:
As the sun is about to set, the solar panel is deflected to a position which toggles switch S1. S1 immediately initiates a timer comprising of IC2 and the associated parts. The timer counts (set by C1 and R5) and waits for some time after which it sends out a command to the motor M1. The motor M1 activates and moves the solar panel back all way round to its original position facing eastwards. The moment it reaches to its ready position, switch S2 is triggered which switches the timer OFF. The next day the whole procedure repeats itself.
The circuit is easily built by fixing the components over a general purpose PCB and interconnecting their leads by soldering as per the circuit schematic. The entire circuit is then housed inside a weather proof enclosure, allowing the appropriate wires for the LDRs and the motors to come out of it.
The LDR assembly is also done as per the diagram.