This paper introduces an intelligent tracking control system for sunlight. The 51 single chip computer is used as the detection and control core. Four photosensitive diodes inside and outside are used to roughly detect and accurately detect the illumination intensity under different weather conditions, so as to enhance the reliability of the system. The motor is controlled to automatically adjust the angle of incidence between solar panels and sunlight to keep perpendicular, so as to maximize the area of receiving light and have tracking precision.
High degree, no tracking dead zone, simple structure, low energy consumption and other advantages, thereby improving the utilization of sunlight. This paper presents the design method of hardware circuit and software of the system. In today’s society, the use of solar energy has spread to millions of households, and there are many ways to use it. There is a common solar stove, solar water heater and so on. In fact, there has been a way of solar energy conversion in nature for a long time, that is, photosynthesis of green plants. However, there is only one kind of energy supporting human society at present, that is, electricity. Ultimately, the use of solar energy will be converted into electricity. It is called photoelectric conversion. However, in the development and utilization of solar energy, the scientific and technological level of human beings is still limited, and low conversion efficiency is the focus of research. Human beings have studied the field of photoelectric conversion for decades.
The main product is solar panels. Numerous schemes have been tried in the manufacturing process and materials of solar panels, but the efficiency is still not up to date. How to set up a simple system framework in existence? Intelligent control of photoelectric conversion system will greatly improve the efficiency of photoelectric conversion. This project studies a solar auto-tracking system, which uses a single chip computer to control two stepper motors to adjust the direction of solar panels from two dimensions, so that it can always cater to the sunlight, achieve the maximum area of sunlight, and ultimately maximize the photoelectric conversion efficiency. It provides a way to improve the efficiency of solar energy utilization device. In the mechanical structure of the solar tracking system, the dual-axis mechanical structure is adopted. The electronic automatic controller is composed of photoresistor detection circuit, AD conversion circuit, 51 single chip computer control circuit, motor drive circuit, automatic manual switch keys and display circuit. The light signal is first captured by photoresistor, converted into electrical signal and sent to AD module for conversion. The digital signal is sent to 51 single chip computer for calculation and processing. The single chip computer finally outputs the corresponding stepper motor control signal through four-way data difference comparison, and drives the mechanical structure to adjust the solar panel to the appropriate angle and direction. Under the automatic working mode, the system can automatically select the working mode according to the real-time weather conditions, automatically track when the light is sufficient or the weather is clear, and automatically enter the dormant mode at night or in cloudy and rainy days, and stop tracking. When the light is sufficient or the weather is clear, the system automatically adjusts the solar panels to be vertical to the sunlight. Maximize the absorption of sunlight.
The mechanical structure and program parts of the system design can run accurately and correctly. In order to reduce its own energy consumption, the system detects light every 10 minutes and adjusts solar panels, thermostatic element with an error of no more than 10 degrees. The system works in a manual way and can adjust the movement of the sun light detection board from top to bottom by keystrokes. The system solar energy automatic tracking block diagram is shown in Figure 1. There are eight photoelectric conversion circuits, each of which has its own operational amplifier and filter capacitor. It is responsible for collecting light signals and converting them into TTL level, which is sent to AD for processing. The distribution of photodiodes is also an important part of the design. The distribution here is a cross distribution. This distribution can detect the value of light in the four directions of east, west, north and south, and then compare a relative set of signals. Finally, the mechanical structure is driven to the strong side of light value. The distribution of photodiodes is shown in Figure 2. D5, D6, D7, D8 are distributed in the inner of the hollow cylinder, responsible for the main preliminary north-west, East-West detection, while D1, D2, D3, D4 are distributed in the outer wall of the cylinder, responsible for accurate detection, the battery plate should be placed in the center of the detection area. The basic circuit of photoelectric conversion is shown in Fig. 3. In the figure, the weak current change of photodiode caused by the change of illumination is magnified by LM324, and the magnification is adjusted by adjustable resistance of R1 to meet the needs of the actual environment. The photoelectric relationship curve of the photodiode is shown in Fig. 4. It can be seen that the current of the photodiode is 0-100 mu A, and the LM324 in the circuit is an integrated operational amplifier, which works in a negative feedback state. Id1: Photoelectric current generated by photodiode D1. R1:50K adjustable resistance. R2:50K constant resistance. Because the system needs real-time conversion of the analog signal of the environment, i.e. the light signal, into the digital signal to be processed by the single chip computer, the ADC0809 chip is selected here. The chip has fast conversion speed and high accuracy, which enables the two motors to accurately locate the direction and angle of the solar panels. The function of AD converter chips is mainly to convert analog signals into digital signals, because single-chip processors can only process digital signals. In terms of types, AD chips can be divided into different levels from accuracy and channel. In terms of processing methods, AD converter chiefly includes sampling, holding, quantization, coding and so on. It is widely used in the conversion of various sensor signals. The circuit design of the AD conversion module connected with ADC0809 and 74LS04 is shown in Figure 5. This design uses stepper motor, which has the advantages of high precision, controllable angle and large torque. Stepper motors actually rotate in a single-double-eight-beat mode. Eight-beat is A-AB-B-BC-C-CD-D-DA-A. Each beat rotates 3.75 degrees, so that the rotation of the shaft can be controlled more accurately. The internal deceleration ratio of eight gears makes the shaft have a certain torsion. The two motors use a ULN2003 driver chip, the 8th and 9th pins of the chip are grounded and the power supply is used. Because ULN2003 is a reverse chip, the pin 1-7 is input, connected to the signal output of the single chip computer, 10-16 pin output, directly connected to the drive cable of the motor. Because the working voltage of the motor is 5V, the VCC of the chip is 5V. The circuit diagram of stepper motor interface MCU is shown in Figure 6. It can be seen from the figure that the control signal of the stepping motor is output from P1 port. If the control signal is weak and the frequency is high and easy to be disturbed, two 74HC14 gates are used to stabilize the control signal and control the motor more accurately. The mechanical part is shown in Fig. 7, fixing and adjusting the position of solar panels in pitch and left and right. Stepping motor A controls pitch and motor B controls left and right. Because the torsion of left and right control is slightly larger, the gears should be accelerated and decelerated to increase the torsion. In the height control of the battery board, the length of the lead screw can be calculated according to the Pythagorean theorem, and the number of rotating cycles of the motor can be estimated by estimating the step distance of the thread. The schematic diagram of the relationship between the effective lead screw length and the height angle of solar panels is shown in Fig. 8. For azimuth calculation, the difference is made between the ray values of the receiving points of two rays on the same axis. The positive number deviates positively and the negative number deviates inversely.
The larger the value, the larger the deviation. The azimuth diagrams of solar panels are shown in Fig. 9. The whole program design includes automatic manual key judgement and indicator display module, solar automatic tracking photoelectric detection conversion module, stepper motor drive module, etc. The flow chart of the automatic tracking software is shown in Figure 10. After the software is running, if the key is detected to be in the automatic working mode, the following tasks are mainly completed. The start and stop of A/D conversion are controlled. The A/D conversion control signal of ADC0808 is provided by 51 single chip computer, which transmits data by interruption. In 51 single chip computer, the output signal of photodiode after A/D conversion is processed. Step 1: Judge the difference between U1, U2, U3, U4 and the set value. If the difference is less than zero, it means that it is already evening or rainy weather. Stop tracking and wait for sunshine.
Step 2: If the difference is greater than zero, it means there is sunshine. Then it judges whether the initial azimuth control signal Ux (U2-U4) and the elevation angle control signal Uy (U3-U5) are zero at the same time.
Step 3: When Ux = 0, motor A stops immediately, is highly locked, and judges Ux for the second time. If it is larger than zero, MCU sends out pulse control motor B forward transmission appropriate angle, while continuing to monitor until Ux = 0. Conversely, control motor B reverse while monitoring Ux until it equals zero. If X direction is adjusted, control Y axis direction in similar direction, adjust Uyde value, make it equal to zero, and then return.
Step 4: If both are equal to zero at the same time, judge whether Upx is zero and if it is greater than zero, then control the motor to rotate at a small angle, while judging Upx until it is equal to zero, and if it is less than zero, then control the motor to reverse slightly until Upx is zero. Upy also uses this set of schemes to make precise adjustments. Step 5: After the rough adjustment and the precise adjustment are completed, the system will temporarily stop the adjustment in order to reduce its power consumption, and adjust again after 10 minutes. When the flashlight is illuminated vertically on the battery board equipped with photoelectric sensors, D2 and D4 (D1 and D3) receive the same illumination and D6 and D8 (D5 and D7) receive the same illumination. When the flashlight deviates from the vertical direction of the battery board at a small angle, motor A drives the battery board to adjust the pitch angle to the light position, while motor B rotates a larger angle clockwise until the light reaches the light level. The battery panel is vertical. When the flashlight deviates from a larger angle, the photodiode in the barrel can not receive light. The control motor automatically adjusts the angle of the solar panel. When the solar light deviates from the vertical direction of the solar panel at a small angle, the system automatically switches to D4 and D6 for detection and tracking to ensure that the solar panel and the light are in a vertical position. When the speed of the flashlight is less than 5 cm/s, the tracking error of the system does not exceed 1 degree after 25 times of repeated operation. When the speed of the flashlight is between 5cm/s and 15cm/s, after 25 times of repeated operation, the tracking error of the system does not exceed 2 to 3 degrees. By testing the performance of the system, it is reliable and stable, and the automatic tracking accuracy and detection of solar rays can meet the requirements. Intelligent control of traditional mechanical structure effectively compensates for the deficiency of orientation of traditional mechanical structure.
Using 51 series MCU control, photodiode capture signal, device selection is more economical, which greatly reduces the cost of the whole system. At the same time, the design of the system is simplified, which greatly reduces the incidence of failure. This system uses two-axis drive, which can track sunlight without dead angle to ensure that solar panels can accurately align with the sun. At the same time, according to the specific weather conditions and different seasons of light, the control mode is selected. In cloudy or insufficient light conditions, because the photoelectric detection circuit will not produce feedback signals, the trajectory adjustment generated by the photoelectric tracking system is zero. Stop tracking, which further optimizes the control scheme scientifically. Photoelectric efficiency has been greatly improved because of this design. The system can be used to supply power to unmanned TT&C stations, unmanned traffic lights, and even solar panels on spacecraft. Human beings have made a step closer in the use of solar energy.