The use of microcontrollers to achieve intelligent control of street lights is receiving more and more attention, and the high stability, low cost and simplicity of operation of the control system have become the main objectives of the design. According to the structural characteristics of avr microcontroller, we introduce the design principle of a networked street light control system in detail by using networked design ideas. The control system has good stability and high practical value.Street light working status detection module circuit
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The working status detection circuit is mainly used to determine the working status of the street light by detecting the working current of the street light. The current detection circuit is mainly composed of linear Hall magnetic sensor ugn3501t, clamped cold-rolled silicon steel and signal processing circuit, the circuit is shown in Figure 4. In the circuit, the Hall element is placed in the gap of the clamped cold-rolled silicon steel sheet, when there is a current flowing through the wire, it will generate a magnetic field in the clamped circle, the size of which is proportional to the current flowing through the wire, the magnetic field acts on the Hall element to induce the corresponding Hall potential, after the operational amplifier ua741 amplification, added to the comparator composed of operational amplifier ua741. When there is current flowing in the circuit, the comparator output signal s1 goes high and is sent to the pb1 terminal of the atmega8. When the street light is on, there is current in the supply line, the current detection circuit outputs high level, and vice versa, the output level is low.
2. 3 Working principle of microcontroller atmega8 and interface circuit
The atmega8 is a member of the AVR high-end microcontroller with 8 kbyte of flash memory. In the terminal controller, it is mainly used to judge the working status of the street light, time the lighting time of the street light, communicate with the upper transmitterii and control the relay work. The working status of the street light is determined by the microcontroller based on the output signal f1 of the light control circuit and the output signal s1 of the status detection circuit, i.e., the status of the pb0 and pb1 ports. pb0 and pb1 are related to the working status of the street light as shown in Table 1. Communication between the microcontroller and the upper transmitter. On the one hand, it receives the timing initial value and control signal of the street light from the upper transmitter ii; on the other hand, according to the logic level of the pb0 and pb1 ports, the working status of the control street light (normal for oxaa, abnormal for oxff) and the local number are sent to the upper transmitter ii. The communication between the terminal microcontroller and the upper transmitter adopts the rs-485 method, and its level conversion interface circuit is shown in Figure 5. shown in Figure 5. In the figure, the level conversion of rs-485 is done by sn75176, and the circuit is half-duplex communication, that is, when pb2 is “0”, it is in data receiving state, and when sending data, pb2 is set to “1”. After sending, pb2 returns to “0” and waits for data to be received. Abstract: This paper introduces the main functions, structure principle and hardware and software implementation of the MSP430-based remote intelligent monitoring terminal for street light decoration lights. The system is put into operation, stable and reliable, with good application and promotion value.
Keywords: monitoring terminal; microcontroller; MSP430; city street light
1 Introduction
With the development of social economy, the function of urban lighting facilities has changed from simply lighting-based to achieving the purpose of beautifying the environment, improving the image and activating the night market economy. The management and control of urban lighting is in urgent need of a scientific, rational and efficient method. Therefore, it is extremely important to provide an effective and reasonable control and management method to remotely monitor the operation status of city street lights and decorative lights. For the characteristics of urban street lights and decorative lights, such as “many terminals, wide area, outdoor, scattered, small amount of information”, the overall choice of wireless communication method is more appropriate. But the street light for single light control and adjacent building lighting control, you can use the wired communication mode. In this way, not only overcome the traditional street light control method, control mode single and can not meet the weakness of real-time monitoring and management requirements, but also can adapt to the requirements of modern city team lighting control. The wireless monitoring terminal is the lower computer of the lighting monitoring system, which is an important link to ensure the timeliness and accuracy of switching lights, saving energy and improving the lighting rate and other indicators.
2 Structure principle and working process of monitoring system
The street light monitoring system mainly consists of central control room and monitoring terminal, which is divided into street light monitoring terminal, decoration light monitoring terminal, decoration light extension terminal and street light single light control terminal according to the usage, and its system structure is shown in Figure 1. The dashed basket is the monitoring terminal. The dotted line in the figure indicates wireless communication, and the solid line indicates wired communication.
The communication between the central control room and the street light and trim light monitoring terminal uses VHF/UHF radio for data exchange. The data transmission rate is 1200Bps, and the modulation mode is FSK, working in heterodyne duplex mode. Since the peripheral sites are scattered, the communication system adopts a large area system, and its structure is a star topology with one point to multiple points. Serial communication is used to exchange data between the decorative light extension terminal and the decorative light monitoring terminal. The data exchange between street light monitoring terminal and single light controller is realized by power carrier communication technology.
3 Hardware design of the monitoring terminal
Since the monitoring system terminal is used to control street lights and trim lights, and the control requirements of street lights and trim lights are different, the hardware design of the street light monitoring terminal and trim light monitoring terminal is different.
3.1 Lamp monitoring terminal and its extension terminal
The ornamental light monitoring terminal is both the remote measurement and control unit of the system and has the ability of self-operation. The hardware mainly includes wireless communication circuit, data sampling and A/D conversion circuit, control output circuit, keyboard and display circuit, etc. Its structure is shown in Figure 2.
The sampling circuit collects the total circuit current and voltage quantities and the electric flow of all branches in real time. The signals are sent to the A/D converter port of MSP430 through V/I transmitter, multiplexer switch and signal conditioning circuit. Each terminal can output four different control methods (such as hourly light, midnight light, etc.). The core part of the wireless communication circuit is the modulation/demodulation chip and Motorol’s GM950i radio. In addition, two RS- 485 ports are designed to be used for system expansion and remote meter reading respectively.
The decorative light extension terminal is suitable for the situation where the distance between two sites is close and it is easy to lay cables, or the wireless communication signal cannot reach (such as basement, etc.), and its structure is roughly the same as the decorative light monitoring terminal, which is connected to the monitoring terminal through RS-485 port, so the decorative light monitoring terminal does not need a radio, which can greatly save costs.
3.2 Street light monitoring terminal and single light control terminal
The street light monitoring terminal is a single light management unit added to the structure of the decorative light monitoring terminal. The single light management unit adopts AT89C51 microcontroller and exchanges data with MSP430 through serial communication.
The single light control terminal realizes the single light control of street lights, and its structure is shown in Fig. 3. The current and voltage signals are converted into digital signals by A/D converter through the current and voltage transformer to the signal conditioning circuit. The switching circuit mainly collects various switching quantities, such as lamp pole tilt, switch closing, etc. The address coding unit is mainly used to set the address of the single lamp control terminal. The communication module is mainly composed of SSC P300 and SSC P111 chips for power carrier communication, which mainly completes the communication between the street light control terminal and the single light control terminal. The relay output unit controls the switching of street lights.
