Foreword
The remote automatic meter reading system is an important symbol of building intelligence. Due to factors such as industry barriers, most of the cities in our country use door-to-door meter reading, which wastes a lot of manpower, causing time delays for electricity, water and gas companies, and increasing the burden on the property management department. Caused by some inconvenience of residents, the remote automatic meter reading system effectively solved these problems.
The digital pulse electric meter, water meter and gas meter are designed to realize the on-site automatic collection of the three meter data. After the home intelligent controller collects the pulses sent by each table, it is converted into real three-table data and stored in the E2PROM. When the property management center monitors and manages the computer to inquire, the family intelligent controller transmits the data to the monitor and management computer through the LON network.
LonWorks automatic meter reading node and system
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 the LonTalk protocol, and completes network message processing, user-defined various calculations, and I / O event processing functions for event scheduling. The schematic diagram of the LonWorks node is shown in Figure 1. Among them, the main control module is used for communication and control; the microcontroller 89C51 realizes the processing and driving functions of input / output data, the count of 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 nodes into the network.
In the meter reading module, FFT-IO transceiver (Figure 2) can be used, which is suitable for twisted pair media; or PLT22 transceiver (Figure 3), 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 number of pulses in the RAM of the meter reading module, and accumulates them into different time periods according to the set segment time and the current moment to realize the counting in different periods. The memory of the meter reading module has a power-off protection function to prevent the accumulated value of the pulse from being lost during 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 the illegal data to deal with the communication abnormalities accordingly.
There are many and scattered data collection modules in the automatic meter reading system, and the real-time requirements for data transmission are not high, and each transmitted and received data is required to be error-free. When the host computer performs data collection, the data saved from the concentrator can be sent directly to the computer without reading the meter reading data directly 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 the collection of 24 analog quantities, analyzes its 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 the synchronous serial I / O mode, and uses the Neurowire main control mode, that is, the main control module drives the synchronous clock input and chip select signal output, and the 89C51 receives the synchronous clock input. The IO8 pin of the Neuron chip in the main 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, add check code in the protocol frame to ensure the correctness of the communication data, as shown in Figure 4.
Conclusion
The automatic meter reading system is composed of a community management computer and an automatic meter reading module. It has a two-level network and adopts a free topology structure. On the management computer, it can query the real-time readings of each household's water meter, electric meter and gas meter. The three tables can also be interrupted in the management center.
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