Design and Implementation of LED Street Light Simulation Control System

As an important public facility of the city, the city's street lighting system will continue to develop with the development of the city, and will develop towards energy saving and intelligence. In recent years, with the implementation of the national low-carbon economic development strategy and the implementation of green lighting projects, urban street lighting systems are also constantly developing in the direction of energy saving, high efficiency and environmental protection.

This paper takes the current popular LED street lighting system as the research object, and designs a set of analog control system, which makes the lighting system have timing control, automatic control with environment and light, automatic control according to traffic flow and fault alarm, and can accurately indicate the fault location. Features. In this paper, 1W LED lamp is used to simulate the actual street lamp, and two street lamp branches are designed.

2 system hardware design 2.1 overall scheme The system is controlled by single-chip microcomputer, which consists of branch controller and unit controller. The branch controller consists of the minimum system module, display module, clock circuit module, natural light signal detection module, keyboard module and sound and light alarm module. The unit controller is composed of a minimum system module of the single chip microcomputer, a constant current source module, a fault detecting module and a pyroelectric infrared detecting module. Serial port communication is used between the branch controller and the unit controller. System block diagram such as. 1 is shown.

Li Xiansheng, Master of Engineering, School of Electrical Engineering, Guangxi University, Lecturer, Guangxi Vocational and Technical College 2.2 Hardware Design 2.2.1 Branch Controller Hardware Design The main control chip of the branch controller adopts 51 single-chip microcomputer, model STC89C58RD+. It can automatically turn on and off according to the change of environment, and the detection circuit of natural light signal is added to the system. The photosensitive element uses a photoresistor. In order to avoid the malfunction of the controller and the anti-interference ability of the circuit, the detection circuit uses a voltage hysteresis comparator.

The circuit is as shown.

The time information of the branch controller is generated by the RTC chip DS1302. Compared with the time information generated by the internal timer of the single-chip microcomputer, the scheme has the following advantages: First, the clock chip can greatly reduce the busyness of the single-chip microcomputer, so that the single-chip microcomputer can be more timely. The status of various modules is detected and the corresponding processing is performed. Second, the accuracy of time is higher. In addition, the DS1302 comes with 31 bytes of RAM for backup of a small amount of data.

2.2.2 unit controller hardware design unit controller is controlled by single-chip microcomputer, model is AT89C2051. The circuit design of unit controller is described as follows: constant current source circuit design constant current source circuit as shown because the light source adopts 1W LED lamp, the maximum work The current is 319mA, the working voltage is about 3.4V, and the constant current source is powered by +6V DC. To reduce the power consumed on the sampling resistor R5, when designing the circuit, the resistance of 3D is selected, and the power is 1W. R1 and R2 are Designed to attenuate the voltage from the D/A converter. When the circuit outputs the maximum power, the feedback voltage obtained by the inverting input of the op amp is about 1V, and the maximum output voltage of the D/A converter is 5V, so the parameter ratio of R1 and R2 is 4:1, and 4KD is selected here. And HC1 can filter out the interference signal to ensure that the normal operation of the circuit does not cause the op amp to output a negative voltage due to the interference signal, and the transistor is turned off. The power of the constant current source is controlled by the D/A converter MAX517, and the control precision is high. The output current calculation formula is: I=Ur5/R5. In the figure, Q3 is introduced to solve the problem that the constant current source cannot be completely turned off.

The fault detection circuit design may be caused by a short circuit or an open circuit when the light is not bright. The detection of the fault must take into account both of these situations. When the lamp is short-circuited, the collector voltage of the Q2 is Vc=6V, which is normally about 2.6V. According to these parameters, the design circuit is as shown, the detection signal is converted to high and low level and sent to the external interrupt of the MCU. mouth. The regulator tube in the figure selects the regulation value of 5.1V, leaving a margin for the Vc value under normal conditions, ensuring no false alarm. The working principle of the circuit is: under normal working condition, the voltage regulator tube will not be broken down, the triode is cut off, and the single-chip interrupt port obtains a high level; when the lamp is short-circuited, the voltage regulator tube breaks down, the triode is saturated, and the single-chip interrupt port is obtained. Low level, triggering an interrupt.

In the same way, as long as the voltage change of the circuit when the lamp is open is provided, an alarm signal can be provided for the single chip microcomputer. After analysis and actual measurement, when the lamp is open, the voltage at the output end of the middle operational amplifier changes significantly. When the circuit works normally, the voltage at the output of the op amp is less than 4V. When the lamp is open, the terminal is 10V. According to this, only the circuit with the same circuit structure can be used to detect the voltage of the voltage regulator D and R1. status. R1 can take 500D, D can be 8.2V, and the detection point of the circuit is the first leg of TL082.

Light short circuit detection circuit Each unit controller of the system detects traffic conditions through two sets of pyroelectric infrared detection probes. When the pedestrian enters a certain street light illumination range, the street light automatically lights up. When the pedestrian leaves the street light illumination range, the light is automatically turned off. Maximize energy savings. In order to add the probe's detection distance, a Fresnel lens is added to the pyroelectric infrared sensor during installation. The circuit of the pyroelectric infrared probe and its installation schematic are shown in and.

3 software design 3.1 program design ideas 3.1.1 branch controller part of the branch controller program mainly includes clock chip DS1302 driver, LCD1602 display driver, keyboard and its function program, optical signal judgment program and serial communication program. The design idea of the branch controller program is: after the controller is powered on, the time information of the clock chip is read immediately after the initialization of the single chip microcomputer is completed, and the working state of the unit controller and the state of various control information are detected, and if an abnormal state occurs, The alarm message is displayed or the switch light control command of the control unit controller is issued through the serial port. Otherwise, the time calendar is displayed and the keyboard is scanned. If the keyboard is pressed, the corresponding function program is executed and the set data is backed up to the RAM of the DS1302. The control information of all the branch controllers to the unit controller is sent out through the serial port of the single-chip microcomputer in the form of commands. The status information sent back by the unit controller is received by the serial port interrupt mode and determines which state information is sent back by which unit. Finally send the display.

3.1.2 Unit Controller Part of the unit controller program mainly includes MAX517 driver, traffic condition detection program and serial communication program. The design idea of the unit controller program is: the controller is powered on, the street lamp is turned off after the initialization of the single chip microcomputer, and the switching light control command of the branch controller and the power parameter of the lighting are waited for, and after receiving the relevant information, the DA conversion is controlled. The device outputs a corresponding voltage signal to control the constant current source for control purposes. When the unit controller detects that the object crosses the specified point, the information is fed back to the branch controller through the serial communication, and then the specified action is performed according to the switch light command sent back by the branch controller.

3.2 program flow. 2.1 branch controller program flow chart branch controller program flow. 2.2 Unit controller program flow test results and analysis Both branches can independently realize the timing switch light control.

When the photoresistor is blocked by hand, the LED light automatically lights up, and when the hand is removed, the LED light automatically turns off.

The power can be adjusted within the range of 20% and 100%. The specific test results of the power indicators are shown in Table 1.

Table 1 Power Test Table Power Setpoint Setpoint (mA) Measured Value (mA) Error (mA) When a fault is set, the fault type and fault street light address can be accurately displayed.

The simulation can realize the automatic switching of the lights according to the traffic conditions, that is, when no pedestrian enters the illumination range of the street lamp, the street lamp is turned off, and vice versa.

5 Conclusion In summary, the system can achieve energy-saving and intelligent control of LED street lights, and achieve higher power control accuracy, system functions have been verified on the hardware platform. The design idea of the system can be applied to the actual LED street lighting system and has high application value. The unit's unit controller is software-addressed and it is easy to expand the number of unit controllers. If you add the bit machine software, the operation is more convenient and more applicable.

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