基于单片机的多功能电能表的设计.doc

摘要 本电能表系统以FM3307／8单片机为核心，对8户居民的用电量进行测量。8路脉冲输出电能计量芯片AD7755能够把居民的用电量转换为一定数量的脉冲，单片机对脉冲进行计数，经过一定的数学运算可以算出用电量。74HC164串入并出8位移位寄存器和LED显示器能够实时循环显示8户居民的用电量。AT24C16通过I2C总线和单片机连接，单片机将居民的用电量实时写入AT24C16，当断电时AT24C16仍能保存数据，再次上电后单片机将其保存的数据读出，从而实现掉电保护。电能表通过RS-485总线与抄表集中器相连，接收抄表集中器下达的抄表（或预付费）、清零等命令。抄表集中器内有GPRS通信模块（MC55），通过GPRS通信网与中心计算机联系，实现数据的上传或命令的下达。 中心计算机根据一天中电费不同价格的时间分割点读取用户的用电量，从而可以实现电能表的复费率功能。如果在电能表外围接入电平控制的低压断路器就可以实现预付费功能（与复费率电能表的程序不同）。中心计算机将用户提前购买的电量写入电能表中，当电量减到0时，控制口（P4）动作切断供电。 关键词：单片机，AD7755，GPRS，复费率，预付费 ABSTRACT The FM3307 / 8 MCU is core of the meter system which measure the power consumption of the eight residents。The power consumption of the residents can be converted to a certain number of pulses by the 8 energy measurement chip AD7755.The microcontroller count the pulses and we can calculate the power consumption after a certain mathematical operations. The 8-bit shift register, 74HC164 and the LED monitor can achieve to show the electricity consumption of the eight residents circularly. The AT24C16 connected to the microcontroller via the I2C bus.The MCU write the power consumption of the residents in AT24C16. AT24C16 can still save the data when power is broken off and the MCU will read the data out after power recovering.So the data can be saved when the power is broken.The energy meter is connected to the meter reading concentrator by RS-485 bus,receiving reading(or prepaiding) Clearing and other command. The meter reading concentrator with GPRS communication module (MC55), communicate with the center computer through the GPRS Communication network achieving to upload data or issue order. The central computer read the users electricity according to division poin of different prices in one day,thus we can realize double rate function. If the electric energy meter peripheral is accessed low voltage circuit breaker,we can realize the prepayment function ( the Program is Difference to the double rate). The center computer will write the power advanced purchased int