In order to realize the automation of campus streetlight control, the author developed a streetlight control system based on power line carrier using PL 2101 chip. The system adopts power carrier communication mode, which connects all the street lamps to the computer, and monitors the working state of the street lamps in the controlled area through the computer, and can set the switching time, the street lamp opening ratio or the opening and closing of a single street lamp at any time. . The working current and temperature of any street lamp can be inquired at any time. When the street lamp is damaged, it can alarm in real time and display the specific geographical location for quick maintenance. When the night (or dark light) is coming and the traffic peaks, the street lights are all. Open, after the peak traffic period, enter proportionally open, such as 7% after midnight in the early morning hours, the street light turn-on ratio can be reduced to 40%, etc., which not only takes into account the lighting needs, but also reduces power waste.
2 system working principle The system consists of three levels, divided into the total control station, the main control station and the slave station. The main control station is composed of a PC, which can be connected to the main control station via optical cable or radio to realize the management of each main control station, and set the switch light time and execute the light-on ratio command, and return to the main control station. The information is summarized and the faulty street light is displayed through the text to accurately determine its location.
The internal structure of the main control station is as shown. The main control station receives the command of the master controller through the optical cable or wireless mode, and monitors the slave station through the serial communication mode of the power line carrier. A communication data packet is composed of 8 bytes of data, the first and second bytes are the identity of the master station, the third byte is the command, the fourth and fifth bytes are the slave addresses, and the sixth to eighth bytes are the data. . In theory, a master station can control up to 60,000 slave stations. The main control station sends the command data by broadcast, and the slave station receives the communication packet and analyzes the data. The content of the analysis is: first, whether the host is its own superior master station, and second, whether the slave address is its own address. The master station executes the command and the corresponding operation only after all the confirmations are correct.
The internal logic structure of the slave station is as shown. Each slave station can control three sets of street lights. It receives the commands of the master station through the power carrier receiving circuit and performs corresponding operations to complete the sampling and processing of the working current. , to determine whether the street lamp is working properly, in order to take reasonable protection measures; at the same time, it can perform on-site working temperature, modem, number of controllers, micro-remote communication, control, main control station, logic block diagram, modem, slave station, logic block diagram, sampling processing In order to take protective measures when the temperature exceeds the normal working range, and return relevant information back to the main control station.
31 Main component selection and performance PL2101 is a new type of direct-sequence spread-spectrum half-duplex asynchronous modem with a carrier frequency of 120Hz, a bandwidth of 15Hz, a transmission rate of 50ps, and a receiving sensitivity of up to 3. In addition, the PL2101 also has a power-on reset. Auxiliary function circuits such as voltage monitoring circuit, watchdog timer and programmable real-time clock. The circuit has strong anti-interference ability, high sensitivity and is compatible with TTL level. In addition, the interface between the PL2101 and the MCS51 series of microcontrollers is very simple, so it can fully meet the system requirements.
The AT8*2051 and 89C55WD series of microcontrollers are cost-effective microprocessors with Flash memory and instructions that are fully compatible with the MCS51. Among them, 892051 has iBFlash memory, which can be used for slave stations. The 8*55WD has 20bFlash memory for the master station.
TLC0832 is an 8bit two-channel three-bus A/D converter, which is characterized by small size, less microcontroller resources and excellent performance.
2 Circuit Design The receiving amplifier circuit in this design is shown. Among them, D7 is used for clamping to prevent excessive surge current; C5L1 and Q1 form an input signal frequency selective amplifier circuit to amplify the input small signal to improve the receiving sensitivity.
The emission amplification circuit is as shown. This kind of emission amplification circuit is very simple, mainly composed of four triodes, and four diodes play a protective role. The slave data processing and control circuit principle is as shown. When the carrier frequency signal received by the PL2101 is processed by the internal circuit, it will demodulate the data bit information by the transmitting and amplifying circuit, and output it through the RXD, and simultaneously output the low level by the HEAD. When the INT1 of the AT89C2051 generates an interrupt and receives the bit, it will synthesize the corresponding instruction information according to the predetermined format. At the same time, according to the time setting specified in the instruction, the time of the switch light and the ratio of turning on the light are modified, and the operation of the switch light is performed. . In addition, it will monitor the current, temperature and other parameters after the light is turned on, so as to implement the protection measures when the standard exceeds the standard, and send the fault cause information to the host computer in time.
The master information processing circuit is as shown. Its modulation and demodulation circuit is consistent with the slave control. In the figure, a Chinese liquid crystal display and a 12-key keyboard are added, which can be used for field circuit parameter setting. The communication with the master control adopts the serial communication protocol, and is transmitted and received by the SBUF through the interrupt, and is converted into the RS-485 level by the SN75176. Its physical structure can be fiber optic or wireless data transmission equipment.
The function of the master controller is to develop the road map of the entire city streetlight control system with VB on the PC. It can accurately and timely display the specific location of the fault and the possible fault cause when a street lamp fails.
33 software design is written in 51 languages ​​and uses all modular programming. The MCU program module in the slave includes the reception of PL 2101 and current and temperature sampling, street lamp control, etc. The main program flow is as shown. The program modules in the main control machine mainly include the reception of the communication data of the master control machine, the scanning and display of the keyboard, and the transmission of data to the slave control machine. The main program flow is as shown. Interrupt the program for it.
4 Conclusion After the development of the city streetlight control system, it has been applied to the small application control system of 860 street lamps. Proof of actual use: The system performance is stable and good.
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