"CONSTRUCTION OF SINGLE AXIS AUTOMATIC SOLAR TRACKING SYSTEM" BY Tanvir Islam & Anik Sarker.
Daffodil International University, Department of Electrical & Electronic Engineering.
The solar tracker comprises comparator IC LM339, H-bridge motor driver IC L293D (IC2) and a few discrete components. Light-dependent resistors LDR1 and LDR2 are used as sensors to detect the panel’s position relative to the sun.
These provide the signal to motor driver IC2 to move the solar panel in the sun’s 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 M when the sun’s 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 M 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 M rotates in the opposite direction (say, clock-wise) and the solar panel turns.