Solar street lamp control system is essentially a small independent photovoltaic power generation system.
Solar street lamp controller is the core component of the whole system. This paper designs a solar street lamp controller based on C8051F700. It mainly introduces the composition of the solar street lamp control system and the hardware circuit design of the controller. The street lamp controller can ensure the reliable and safe operation of the solar street lamp system, and has practical application value. As a new type of energy, solar energy has been widely used because of its rich resources, clean and environmental protection, and small geographical constraints. Solar street lamp is a typical product of solar energy application. It uses solar energy as energy source, charges during the day and uses at night. It does not need complex pipeline laying. It is safe and pollution-free.
It has been loved by people and attached great importance to by the government. This paper introduces the design of solar street lamp controller based on C8051F700, which can realize the functions of scientific management of storage battery and intelligent control of street lamp, as well as the functions of over-current protection and anti-refilling protection. Solar street lamp system is mainly composed of the following parts: solar panels, storage batteries, controllers, LED street lamps. As shown in Figure 1. Solar panels provide energy, storage batteries store energy, and the controller coordinates the work among solar panels, storage batteries and LED street lights in the whole system to make the whole solar photovoltaic system run efficiently and safely. The most important functions of the solar street lamp controller are as follows: controlling the charging of the battery by the solar panel, controlling the discharge of the battery to the street lamp, logic control and necessary protection functions. The hardware structure of the controller is shown in Figure 2. The controller designed in this paper is based on C8051F700 single chip computer. The peripheral circuit includes solar panel voltage sampling circuit, battery voltage sampling circuit, load current sampling circuit, PWM power driving module, output protection power driving circuit, power supply module, keyboard and LED display module. The connection between solar panels and batteries, as well as between batteries and LED street lamps, is realized through the switch of MOSTFET in the controller, as shown in Figure 1.
MOSTFET [2] has the characteristics of low driving power and high switching frequency. It can output PWM signal through I/O port of MCU to realize the control function. The charge and discharge management of the controller is mainly judged by the sample value of battery plate voltage and the sample value of battery voltage. Among them, solar panels have two functions: one is to charge batteries; the other is to use them as photosensitive components to judge whether it is dark or daybreak, so that solar street lamps can be automatically lit at dark and automatically extinguished at daybreak [3]. When the solar panel voltage is higher than the set threshold, it is judged to be daytime, and vice versa, night. According to the battery voltage, it judges whether the solar panel charges the battery and whether the battery discharges the load. The charging circuit is shown in Figure 3. When the controller judges the day according to the collected solar panel voltage, and refers to the size of the battery voltage, thermostatic element it judges the charging mode of the battery, and uses the I/Q port to send high and low levels to control the conduction and shutdown of MOSFET, so as to complete the charging of the battery by the solar panel. PWM control mode is adopted for battery charging. When the battery overdischarge occurs, it is charged to the elevating voltage of the battery for a period of time, then to the direct charging voltage, and kept for a period of time to activate the battery, avoid sulfide crystallization, and finally to the floating charging voltage, and keep charging with the floating charging voltage.
When the battery has no over-discharge action, it does not adopt lifting charging mode, but uses direct charging and floating charging mode only. This control method can make the battery achieve better charging effect and prolong the service life of the battery. When the controller judges night and the battery voltage is within the normal working range, the battery discharges to the LED lamp by controlling the conduction of the MOSFET, and the battery voltage decreases gradually. Once the battery voltage drops to the overdischarge voltage, the controller will turn off the MOSFET, protect the battery and light the corresponding indicator lamp. The power supply circuit of the system is shown in Figure 4. The power supply of the controller is introduced through the positive pole of the battery and through the anti-refilling diode D1. The driving voltage of the transistor is not consistent with the working voltage of the chip. Among them, VAA is the driving voltage of triode. VAA is the voltage of storage battery after D1, and then regulated by voltage regulator. The voltage required by MCU is the voltage stabilized by ASM1117 after VAA, which provides 3.3V normal working voltage required by MCU. The circuit is simple and reliable. In order to ensure the stability of system performance and the extension of service life, lightning protection, battery anti-charging protection and battery polarity anti-connection protection are added in the design of controller, and they have measures of over-charging, over-discharging and over-loading protection, which play an important role in improving the reliability of the system. Controller is an important part of solar street lamp system.
Its performance directly affects the reliability of the system. Its hardware design and software programming are particularly important. This paper designs a solar street lamp controller, which improves the efficiency of solar panels and prolongs the life of storage batteries.