Design And Implementation Of Low Cost Intelligent Building Intercom System

The Intelligent Residential Building Intercom System, as a typical example of access management system, has been widely employed in many fields such as intelligent hospitals, intelligent residential community, intelligent buildings and so on. From the perspective of consumers, residential building intercom system is, while meeting the basic functions, expected to be user-friendly and has a high performance price ratio. In terms of functions, the products of intelligent residential building system available in the market can mostly meet consumers’ demands. Yet due to different designs, there is a great variance in their performance price ratio. According to the specific design requirements of a company, the present paper made an attempt at designing a low-cost Intelligent Residential Building Intercom System.The whole design referred to and absorbed a number of mature access management designs. The communications protocols are formulated according to customers’ requirement. Based on the protocols, the hardware of the system is divided into five parts, including door machine, network switcher, adapter, user machine and management unit.The door machine and user machine’s communication is defined as the local communications, and their communications with the management is defined as the network communications. Adapter is used for grouping each user in accordance with the floors and intelligent controls each user machine. Network switcher is responsible for forwarding network communication’s command, preserving the state of communication as well as switching the communication branch. System communication uses two serial bus, door machine and each floor adapter use the serial-bus-one to send and receive commond,they can hang on or up communications by the judgment of each MCU. Network switcher monitors the serial-bus-one and intelligent records the communication status of the door machine and user machine. When management have a communication with door machine or user machine, management sends the command through the serial-bus-two, According to the stored communication status, network switcher forwards command through the serial-bus-one and waits for the response signal to decide whether to open or close the communication branch, then the network switcher forwards response signal to the management through the serial-bus-two, management performs the appropriate actions according to response signal.With the communications protocols and cost taken into account, cost-effective and easy-procured Freescale8-bit microcontroller MC9S08series were selected as the hardware master chip. The function circuit was composed of the transistor discretes equipped with the necessary chips. By receiving and judging serial bus information, MCU controls the transistor switch circuit, and finally accomplishes the switching of the various communications. Because the system will work continuously once put into use, the power consumption of the system should be included in the scope of cost considerations. Therefore, zero-power standby in the user machine was firstly designed and corresponding software was developed according to hardware circuit. Through reasonable test process, the system tests were completed.Through constant tests and improvements, the Intelligent Residential Building Intercom System was finally completed. With management unit as the core of the network, with communication between door machine, adapter and user machine as the vital section and with the network switcher as network medium, it has achieved a tripartite communication function. Further verified by the power consumption test and cost accounting, the design proved to be rational and thus the design of a cost-effective intelligent building intercom system was completed.