Remote meter reading system based on LonWorks technology

　　Preface

　　The remote automatic meter reading system is an important symbol of building intelligence. Due to industry barriers and other factors, most of the residential buildings in my country use door-to-door meter reading, which wastes a lot of manpower, causes time delays in charging for electricity, tap water, gas and other companies, increases the burden on property management departments, and also causes some inconvenience to residents. The remote automatic meter reading system effectively solves these problems.

　　The design uses digital pulse electric meter, water meter and gas meter to realize the on-site automatic data collection of the three meters. After collecting the pulses sent by each meter, the home intelligent controller converts them into real three-meter data and stores them in E2PROM. When the monitoring and management computer of the property management center makes inquiries, the home intelligent controller transmits the data to the monitoring and management computer through the LON network.

　　LonWorks Automatic Meter Reading Node and System

　　The LonWorks measurement and control unit uses a LonWorks main control module with Neuron chip as the core. The main control module includes transceiver, address decoding circuit, reset circuit, crystal oscillator circuit and E2PROM. The main control module transmits data through LonTalk protocol and completes network message processing, user-defined calculations and I/O event processing for event scheduling. The schematic diagram of the LonWorks node is shown in Figure 1. The main control module is used for communication and control; the microcontroller 89C51 realizes the processing and driving functions of input/output data, counts the pulse input signal, and completes the data transmission with the main control module. The transceiver in the main control module is responsible for connecting the node to the network.

　　In the meter reading module, an FFT-IO transceiver (Figure 2) can be used, which is suitable for twisted pair media; or a PLT22 transceiver (Figure 3) can be used, which is suitable for power line communication media.

　　The meter reading module collects the output signals of each pulse meter in real time, accumulates the pulse number and stores it in the RAM of the meter reading module, and accumulates it to different time periods according to the set segment time and the current time, so as to realize time period counting. The memory of the meter reading module has a power-off protection function to prevent the loss of pulse accumulation value in case of power off. The data concentrator repeatedly polls and collects the data in each meter reading module and saves it in the corresponding memory, and automatically filters illegal data and handles communication anomalies accordingly.

　　The data acquisition modules of the automatic meter reading system are numerous and scattered, and the real-time requirements for data transmission are not high. It is required that each transmitted and received data is error-free. When the host computer performs data acquisition, the data saved in the concentrator can be sent directly to the computer without directly reading the meter reading data from the meter reading module.

　　The meter reading module is specially used for automatic reading of water meters, electricity meters and gas meters. Each module reads 24 analog quantities, analyzes their A/D sampling values, identifies the state of the pulse meter, and detects the on/off state of the line.

　　The communication between the LonWorks bus control module and 89C51 adopts synchronous serial I/O mode and Neurowire master control mode, that is, the master control module drives the synchronous clock input and chip select signal output, and 89C51 receives the synchronous clock input. The IO8 pin of the Neuron chip in the master control module outputs the synchronous clock; the IO9 pin is the serial data output; the IO10 pin is the serial data input; and the IO5 pin is selected as the chip select signal output. 89C51 uses interrupt mode to transmit data and adds a checksum to the protocol frame to ensure the correctness of the communication data, as shown in Figure 4.

　　Conclusion

　　The automatic meter reading system consists of a two-level network consisting of a community management computer and an automatic meter reading module. It adopts a free topology structure. The real-time readings of each household's water meter, electricity meter and gas meter can be queried on the management computer. The three meters can also be disconnected at the management center.