Design of Sun Tracking System Using Single Chip Microcomputer

    Abstract: Aiming at the low utilization rate of light energy in fixed solar energy utilization devices, a solar tracking system is designed. This system is controlled by a single-chip intelligent computer and uses a photoelectric sensor to detect the shadow of the sunshade under the sun, so as to accurately locate the relative position of the sun and the solar energy utilization device, realize the full-process solar tracking of the solar energy utilization device, and maximize the utilization of sunlight.

    With economic development and social progress, natural resources are being developed and utilized in large quantities, even predatory ways. Human natural resources are about to be exhausted. Therefore, it is urgent to find new energy sources. Solar energy, as a clean, environmentally friendly and inexhaustible renewable energy source, plays a wide range of roles in human production and life. Therefore, it is extremely important to rationally develop and utilize solar energy and improve the utilization rate of solar energy. At present, the placement of solar energy utilization devices is mostly fixed, while the relative position of the sun and the solar energy utilization device changes all the time during the day, which makes it impossible to ensure that the solar energy utilization device is always exposed to direct sunlight, thereby greatly reducing the utilization rate of solar energy. In order to improve the utilization rate of solar energy, a solar tracking system is designed to enable the solar energy utilization device to receive direct sunlight at all times and maximize the utilization of solar energy.

    1. Overall design

    The solar tracking system consists of three parts: control module, detection module and execution module. The control module mainly includes the central processor composed of STC89C52 single-chip microcomputer; the detection module mainly consists of photoelectric sensors, position sensors and peripheral circuits under the cooperation of the shading device; the execution module mainly includes stepper motors and drive circuits. Its overall structure is shown in Figure 1, and its prototype is shown in Figure 2.

    Objects under sunlight will produce shadows, and the direction of the shadows is consistent with the direction of the sunlight. Based on this principle, this system uses photoelectric sensors to detect the shadows of the sunshade under sunlight and accurately locate the relative position of the sun and the solar energy utilization device.

    The movement track of the sun in a day can be decomposed into the horizontal direction and the pitch direction. As shown in Figure 3, in the horizontal direction, when the sun's rays directly hit the solar energy utilization device, the shadow of the horizontal shade 3 completely covers the horizontal photoelectric sensor 4; in the pitch direction, when the sun's rays directly hit the solar energy utilization device, the shadow of the pitch shade 5 completely covers the pitch photoelectric sensor 6. When the two photoelectric sensors are completely in the shadow at the same time, the solar energy utilization device is in a direct sunlight state.

    As shown in FIG3 , when the shadow of the horizontal shade 3 does not completely cover the horizontal photoelectric sensor 4, it means that the solar energy utilization device 2 has not reached direct sunlight in the horizontal direction. After receiving the signal transmitted by the horizontal photoelectric sensor 4 at this time, the control module will control the motor in the horizontal direction of the execution module to rotate until the shadow of the horizontal shade 3 completely covers the horizontal photoelectric sensor 4, and the motor in the horizontal direction stops rotating, so that the solar energy utilization device reaches direct sunlight in the horizontal direction; when the shadow of the pitch shade 5 does not completely cover the pitch photoelectric sensor 6, it means that the solar energy utilization device 2 has not reached direct sunlight in the pitch direction. After receiving the signal transmitted by the pitch photoelectric sensor 6 at this time, the control module will control the motor in the pitch direction of the execution module to rotate until the shadow of the pitch shade 5 completely covers the pitch photoelectric sensor 6, and the motor in the pitch direction stops rotating, so that the solar energy utilization device reaches direct sunlight in the pitch direction; when the shadow of the horizontal shade 3 completely covers the horizontal photoelectric sensor 4 and the shadow of the pitch shade 5 completely covers the pitch photoelectric sensor 6, the solar energy utilization device reaches direct sunlight at this time.

    The sunlight is dim on cloudy days, but there is still a clear contrast between the shadow created by the sunshade under the sunlight and the sunlight. Therefore, the system can continue to accurately locate the position of the sun, so that the solar tracking system is not affected by weather changes; when the sunlight is too dim to be suitable for the solar energy utilization device to work, the photoelectric sensor that detects the light intensity transmits a signal to the control module, and the control module stops the solar tracking system from working, reducing the energy loss of the solar tracking system.

    The motion trajectory of the solar tracking system in the horizontal direction: from morning to night, the motion trajectory of the sun is from east to west, and the initial setting trajectory of the execution module is also from east to west, and the initial setting position is towards the east. At night, the execution module is facing the west. The next morning, the execution module facing the west will continue to rotate from east to west at a certain angle to touch the horizontal position sensor. After receiving the signal from the horizontal position sensor, the control module will reset the execution module in the horizontal direction, so that the execution module will continue to track the sun's rotation from east to west. The motion trajectory of the solar tracking system in the pitch direction: from morning to noon, the motion trajectory of the sun is from low to high, and from noon to night, the motion trajectory of the sun is from high to low. From morning to noon, the execution module rotates from low to high following the sun; from noon to evening, the execution module will first continue to rotate from low to high by a certain angle to touch the first pitch position sensor, and after the control module receives the signal from the first pitch position sensor, it will make the execution module follow the sun to move from high to low; the next morning, the execution module will first continue to rotate from high to low by a certain angle to touch the second pitch position sensor, and after the control module receives the signal from the second pitch position sensor, it will make the execution module follow the sun to move from low to high.

    2 Hardware Design of Sun Tracking System

    2.1 Execution module design

    In order for the execution module to drive the solar energy utilization device to track the sun throughout the whole process, the execution module must be able to rotate in both horizontal and pitch directions to meet the sun's horizontal direction: east-west, and pitch direction: low-high-low movement characteristics. Therefore, the execution module is equipped with two stepper motors, and the coordinated rotation of the two stepper motors realizes the movement of the execution module in the horizontal and pitch directions, thereby achieving full tracking of the sun.

    The two stepper motors are driven by two ULN2003 chips, and the two driver chips are connected to the P0 port of the single-chip microcomputer in the control module. Among them, P0.0-P0.3 controls the stepper motor in the horizontal direction, and P0.4-P0.8 controls the stepper motor in the pitch direction, which can rotate or stop under the control signal of the single-chip microcomputer. The driving circuit of the two stepper motors is shown in Figure 4.

    2.2 Detection module design

    The physical structure of the horizontal photoelectric sensor and its matching horizontal shade is shown in Figure 5. The horizontal photoelectric sensor is used to detect the shadow produced by the horizontal shade to determine the horizontal relative position of the solar energy utilization device and the sun.

    The actual structure of the pitch photoelectric sensor and its matching pitch shade is shown in Figure 6. The pitch photoelectric sensor is used to detect the shadow produced by the pitch shade to determine the relative pitch position of the solar energy utilization device and the sun.

    The photoelectric sensor detection circuit with the shading device is mainly composed of a photoelectric sensor, a resistor, a potentiometer and an LM393 chip. When the light intensity received by the photoelectric sensor is greater than the set value, the potential of the -IN pin of the LM393 chip is lower than the potential of the +IN pin. At this time, the OUT pin of the LM393 chip outputs a high level; when the light intensity received by the photoelectric sensor is less than the set value, the potential of the -IN pin of the LM393 chip is higher than the potential of the +IN pin. At this time, the OUT pin of the LM393 chip outputs a low level. The -INT pin and +IN pin of the LM393 chip are connected to the P2.0 and P2.1 ports of the microcontroller respectively. The detection circuit of the two photoelectric sensors is shown in Figure 7.

    According to the movement trajectory of the sun, the rotation angle of the execution module in the horizontal direction is 180 degrees. Two position sensors are installed in the horizontal direction of the execution module to limit the horizontal movement range of the execution module; the rotation angle of the execution module in the pitch direction is 90 degrees. Two limit sensors are also installed in the pitch direction of the execution module to limit the pitch movement range of the execution module.

    2.3 Control module design

    The control module is based on a STC89C52 chip. After receiving the signal from the detection module, it processes the signal to activate the two stepper motors of the execution module, thereby ensuring that the solar energy utilization device receives the maximum intensity of light. The single-chip microcomputer system used in the control module consists of four parts: STC89C52RC chip, power supply circuit, reset circuit, and crystal oscillator circuit.

    3 System Software Design

    The software of the control system mainly consists of a main program and some subroutines. The main program consists of some state selection statements and loop statements, which mainly re-detect the relative position of the execution module and the sun after the system is reset. When the sensor sends back the corresponding information such as light and position, STC89C52 responds to the corresponding signal and controls the rotation of the stepper motor. The main function of the subroutine is to control the action of the execution module through the forward and reverse rotation of the motor, so that the solar energy utilization device can move in combination in the horizontal and pitch directions.

    The program flow chart is shown in Figure 8.

    4 Conclusion

    The innovation of the solar tracking system is that it imitates the sunflower, follows the law of the sun's movement, uses a photoelectric sensor to detect the shadow of the sunshade under the sun's irradiation to accurately locate the relative position of the sun and the solar energy utilization device, and realizes the full solar tracking of the solar energy utilization device through the intelligent control of the single-chip microcomputer. The main function of this system is to improve the utilization rate of solar energy to alleviate the current energy shortage. Applying it to solar power stations, solar street lights, solar water heaters, solar cookers and all fixed solar panels can greatly improve the utilization rate of these devices. As people's awareness of energy conservation and environmental protection continues to increase, it will be applied to a wider range of occasions.