Which Transducer Sensors to Use for Your Solar Tracker Which Transducer Sensors to Use for Your Solar Tracker

A solar tracker improves the performance of solar energy systems by aligning the collector panels directly with the sun throughout the day. A single-axis tracker can improve the efficiency of a solar power system by 20 percent, and a double-axis tracker can improve the efficiency of a solar power system by 40 percent. The solar tracker system is based on two optical sensors mounted on a programmable controller. The controller is also wired to the actuator of a motor. This motor turns the collector array based on the output voltage of the controller. You may want to build your own solar tracker. Perhaps you've purchased a professionally designed tracker and the sensor has failed after the warranty expired. In either case, you must choose an appropriate optical sensor for your controller and motors.

Principles of Transducer Sensors

The optical sensor is referred to as a transducer because it can translate the light energy of the sun into the mechanical energy of the motor. The optical sensors are typically either light-emitting diodes or light-dependent resistors. When these semiconductors are exposed to sunlight, they absorb photons. These photons increase the energy of electrons, causing them to jump into the conduction band. This causes a voltage to flow through the circuit. You can use regular household LEDs in some tracking systems. However, the most common sensors are photoresistors made of cadmium sulfide or gallium arsenide. The resistance of these components is inversely proportional to the intensity of light they receive. When the resistance cannot decrease any further, the resistor has reached light saturation. The photocell for any particular solar tracker system is chosen based on its dark (maximum) resistance and light saturation (minimum) resistance. The photocell is connected in series with a capacitor.

Moving the Tracker

The tracker usually has two sensors for each axis of motion. The printed circuit board subtracts the voltage across a pair of sensors. Depending on whether net voltage is positive or negative, the motor turns clockwise or counterclockwise. The controller is programmed to maximize solar flux by constantly turning towards the highest voltage. However, it is also programmed with short delays to prevent the tracker from wobbling on cloudy days. Some trackers can be programmed by plugging the controller into a PC installed with the appropriate software.

Obtaining Replacement Sensor

Replacing the sensor on a solar tracker is a complex task. It requires both theoretical and practical knowledge of electromechanical controls. The output voltage of the replacement sensor must be compatible with the controller settings. Attempt to obtain replacement sensors directly from the manufacturer. This is the best option. If this is not possible, obtain the specifications for the old sensor. Determine whether you are using an LDR or an LED. Check its ratings for amperage and voltage. If you are using an LED, choose one of the same color. The wavelength of light affects the amount of energy transferred to an excited electron. Consult with the tracker's distributor and installer for help identifying and obtaining the replacement parts.

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