Design of intelligent LED solar street light controller

The solar LED street lighting system adopts the complementary mode of commercial power, which has practical and economic significance for promoting the application of solar LED street lamps. In order to realize the complementary control of the commercial power of solar LED street lamps, a commercial street complementary LED solar street lamp controller was designed. The controller takes the ARM processor as the core, and samples the parameters such as battery voltage, solar cell voltage and ambient temperature to enter the ARM operation decision, which can realize high-accuracy control of temperature compensation correction, and has battery selection function and mains supply. Automatic switching function. The controller is applied to the retrofitting of street lamps, which can reduce one-time investment and achieve significant energy saving and emission reduction effects.

As a kind of “inexhaustible and inexhaustible” green and clean energy, solar energy is rapidly becoming widely used. LED has the characteristics of small size, sturdy and durable, low power consumption, long life, environmental protection, and good light color performance. The output of the solar cell is direct current, and the LED is also a direct current driving source. The two are easy to match, and the high utilization rate can be obtained, and the cost is reduced. Therefore, the LED solar street lamp has received more and more attention.

Because solar energy is restricted by weather factors, the distribution density of sunlight is small, and the time and intensity of light reception are random and intermittent. To ensure the stability of the output voltage of solar cells, it is necessary to use batteries to store electrical energy. Charge the battery and discharge the battery at night. If continuous rainy weather is considered, the battery capacity requirement is even greater, and the solar battery pack capacity is larger and the cost is higher. The solar LED street lighting system adopts the complementary mode of the city power to better solve this contradiction, and has practical and economic significance for promoting the application of solar LED street lamps.

The composition of the municipal complementary LED solar street light system

The so-called mains complementary LED solar street light system is based on solar cell power generation, supplemented by ordinary 220V AC power supplemented LED street lighting system. With this system, the photovoltaic battery pack and battery capacity can be designed to be smaller, basically There was sunshine during the day, and solar energy was used to charge the battery at the same time. When it was dark, the battery discharge turned the load LED on. In most parts of China, there are basically more than 2/3 of the fine weather throughout the year, so that the system has more than two-thirds of the time to illuminate the streetlights with solar energy, and the remaining time is supplemented with energy from the mains, reducing The one-time investment in solar photovoltaic lighting system has significant energy saving and emission reduction effects, and is an effective method for promoting and popularizing solar LED street lighting at the current stage.

LED solar street light system is shown in Figure 1. It consists of five parts: solar cell, street lamp controller, battery, mains supply, switching power supply and LED street light. Among them, the street lamp controller is the control core of the whole system, which is used for charging and discharging control of the battery, lighting control of the LED street lamp, automatic switching control of the mains power supply and related protection control; solar cells are used to convert solar energy into electric energy And the street lamp controller determines whether it is day or night by collecting the voltage of the solar cell; the battery is the energy storage device of the whole system, the solar battery charges the battery during the daytime, and the LED street lamp is powered by the battery at night or in the rainy day, and the street lamp is controlled The device can collect the battery voltage and switch to the mains supply when the battery is insufficiently powered.

Figure 1 Mains complementary LED solar street light system

Street lamp controller hardware design

The hardware block diagram of the solar street light controller is shown in Figure 2. It is mainly composed of power input, data acquisition display control, ARM processor and output. The controller takes the ARM processor as the core, collects the battery voltage, solar cell voltage, ambient temperature and other parameters through the ARM microprocessor, and makes the ARM operation decision, selects the temperature compensation parameter that meets the battery characteristics, and realizes high-accuracy control. At the same time, adopts The intelligent and efficient PWM fuzzy charging method charges the battery to ensure that the battery works optimally. The controller has buttons and display circuits, which can easily set the operation mode and operating parameters, and the display circuit can also visually display the current operating status.

Figure 2 Hardware block diagram of the solar street light controller

2.1 power input section

The power input part includes a reverse connection protection circuit for protecting the mains input, the battery input, and the solar cell input, and a charge and discharge and power supply switching circuit. The charging, discharging and power supply switching circuit realizes the switching of the commercial power supply and the battery power supply, and realizes the charging control of the battery by the solar battery and the discharge control of the battery, and at the same time supplies power to the MOSFET voltage regulation and short circuit protection circuit of the output part.

2.2 data acquisition display control part

The data acquisition display control part includes control buttons, LED display circuit, voltage and current acquisition, temperature acquisition, sensitization acquisition and equalization circuit. The control buttons include a test button, a menu selection button, and a parameter selection button. The test button can make the controller enter the test state; the menu selection button is used to select the working mode. Each time the menu selection button is pressed, the mode value will be changed once, and the corresponding parameters in the mode will also be displayed. At this time, the parameter is pressed. Select the button to set the operating parameters in this mode; the important data such as the operating mode and parameters of the system are stored inside the chip, and are not lost after power failure, making the adjustment more convenient and the system work more reliable. The LED display circuit includes the status display of 5 LEDs and the operation parameters of 2 digital tubes. The 5 LEDs are used to display the working status of solar cells, battery, mains, load 1, load 2, and 2 digital tubes. When the parameter setting is made, the mode and the parameters in this mode are displayed separately, and the temperature is displayed when the parameter setting is not performed. Voltage acquisition, current acquisition, temperature acquisition, and sensitization acquisition respectively complete the collection of battery and solar cell voltage, discharge current, temperature state, and illumination, and these signals are processed by ARM processor. The voltage and current acquisition circuit is ARM processor. Control to control whether the equalization circuit works.

2.3 ARM processor part

The ARM processor uses Philips' ARM chip LPC2134, which is a high-end 32-bit real-time processor that is at the heart of the entire system. Analyze and process the data collected by the acquisition module, make corresponding decisions, control the charge and discharge and power supply switching circuit, voltage and current acquisition circuit, MOSFET voltage regulation and short circuit protection circuit and soft switch to realize charge and discharge control and control of the battery Protection control of the device, on/off control of the output load. When the solar cell cannot supply power to the load normally, the mains can automatically supply the load to the load instead of the mains directly through the charge and discharge and power supply switching circuit, voltage regulation and short circuit protection circuit and soft switch on the controller. The access mode can reduce the damage caused by the mains to the battery and the mains power, and can effectively reduce the power supply configuration of the mains. The entire switching process achieves soft switching, which does not impact the load and the battery, and the load operation is not affected.

2.4 output section

The output section includes MOSFET regulation and short circuit protection circuits and soft switches. Under the control of the ARM processor, the MOSFET regulator and short-circuit protection circuit realize short-circuit protection and regulated output, and the soft switch realizes independent on-off control of dual output.

Street lamp controller software design

After completing the self-test and initialization procedure, the controller reads various set parameters, such as working mode, battery type, etc., and then enters the day and night judgment program, and enters the daytime processing program or the night processing according to the determined situation. program. The judgment of day and night can be judged by reading the voltage at both ends of the solar cell, or can be judged by the photosensitive sensor interface signal reserved by the acquisition controller. The daytime and nighttime judgment procedures judged according to the voltage of the solar cell are as shown in FIG. .

Figure 3 day, night judgment program flow

The daytime processing program is shown in Figure 4. After entering the daytime processing program, first turn off the LED street light and turn on the interrupt corresponding to the test button, then collect the voltage U1 of the solar cell, the voltage U2 of the battery, the ambient temperature T, according to the ambient temperature T and temperature. The compensation coefficient (lead-acid battery -5mV/°C, lithium battery -4mV/°C, this coefficient can also be adjusted in the program) to calculate the battery float point voltage Uf, overcharge protection voltage Uhvd, and according to the collected U1, The size relationship between U2 determines whether the charging process is executed. After entering the charging state, it is determined whether it is direct charge, floating charge, or overcharge protection according to the size of U2.

Figure 4 day processing procedure

Figure 5 black night processing procedure

The night processing program is shown in Figure 5. After entering the night processing program, first judge whether the lighting delay time has expired, if not, then wait until the lighting delay time expires, the lighting delay time is up, then collect the battery voltage U2, the ambient temperature T, according to the environment The temperature T and the temperature compensation coefficient are calculated to determine the battery over-discharge protection voltage Ulvd, and according to the acquired U2, it is determined to enter the over-discharge protection, switch to the mains supply or turn on the battery discharge to turn on the LED street light, and the LED street light is turned on and then judged to turn off the light. When the time is up, if the turn-off time is up, turn off the LED street light, and the two LED street lights can be controlled separately.

The controller can also increase the dual-time control function of the two loads when designing the software program. The dual-time control means that both the night lighting time and the morning lighting time of the two loads can be set, and the load is set to the dual-time function. Turn off the lights after a period of time, turn off the lights before dawn, wait until the day to turn off, and the lighting time is adjustable. The schematic diagram of the dual-time control is shown in Figure 6. The controller can realize pure light control by monitoring the light control points, and can also realize light control and dual-time timing coordination control. The light control point refers to the voltage value of the solar panel when the light is on at night. The user can adjust the light control opening voltage according to the actual environment. For example, when the solar panel has other light interference at night and the light cannot be turned on, the value can be increased and filtered. The stray light interferes, but the turn-on time may be advanced. The light control judgment time refers to the time that the panel voltage needs to be judged when the voltage reaches the light control point. The longer the time, the better the filtering effect. The smaller the value can achieve the purpose of turning on the light in advance, but it is easily interfered by external stray light. Delayed turning on the light means turning off the light at a certain time in the evening. Adjusting this time can achieve the purpose of delaying the turning on of the light.

The controller also has a test function, and the test button adopts an interrupt mode. When a test button is pressed, the test state interrupt service routine is entered. During the day, press the test button on the controller to directly open the LED street light load, and press it again to turn off the load. After opening, there is no button to close the load, then it will automatically close after 1min, which is convenient for on-site construction test. The software flow of the test function is shown in Figure 7.

Figure 6 Schematic diagram of dual time control
Figure 7 test function software flow

After the controller is powered on, the working mode and related parameters can be set by pressing the button. The controller software program is designed to add a battery selection program to support the use of sealed batteries, open batteries, gel batteries, lithium batteries, etc. Before use, you must select the correct battery type and press the menu selection on the control board. The key enters the battery type selection mode, and then selects the battery type by pressing the parameter selection button set on the control circuit board. After the setting is completed, wait for 30s, the parameter will be automatically saved, and the controller will be based on the set battery parameter during operation. The matching of the parameter operation is automatically selected by the ARM processor program. When the set battery is a lithium battery, the ARM processor will send a control signal to make the equalization circuit effective, so that the capacity of each battery of the lithium battery is balanced, and the service life of the lithium battery is prolonged.

Conclusion

The LED street light controller designed in this paper has a battery selection function, supports a variety of different batteries, and has a temperature compensation function, which can effectively extend the service life of the battery, and has a complementary switching function of the commercial power. The controller is applied to the retrofitting of street lamps, and the original electric power supply line and the light pole can be kept unchanged, and the LED light source is replaced, which constitutes a complementary LED solar street lamp of the city, and the investment will be greatly reduced, and the energy saving effect is remarkable.

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