The Remote Control System Based On Wireless Sensor Networks

In the traditional industrial wiring, cable networks have the characteristics that wiring is difficult, construction is not possible in some special situation and wiring can't be done for the influence of obstacle in engineering refitting. In this time, carrying out a part of network cabling wirelessly can make it possible to realize remote control on equipments in factories. On the other hand, equipments in factories have some special requirements on the special environment. For example, in factories, temperature, humidity, the light intensity and so on are required to be controlled in a special range.Remote control system is designed according to the requirements above. Remote Control System which is based on the technology of RF communication, wireless sensor and bus of RS485 has many functions such as serial communication, wireless communication and RS485 bus simulating. Using the technology of wireless sensors and RF communication, data in wired network is connected to wireless unit, and then relayed by wireless unit. So, it can extend the wired network in particular situation.The development of Remote Control System is mainly composed of two parts: hardware development and software development. Hardware platform is composed of MCU and wireless ratio frequency module. MSP430f149 produced by TI is selected because of its incomparable advantages that any other MCU does not have. The first, it has ultra-low power consumption, the second its timing system is designed specially, and there are also plentiful outer modules the working of which can be set to requirements.Wireless transceiver module is composed of CC2420 chip, 2.4GHz RF antenna and corresponding impedance matching circuit. Peripheral circuit of the chip consists of crystal oscillator clock circuit, ratio frequency in/out matching circuit and microchip interface circuit. The main function of wireless unit is receiving data which are transferred by bus of RS485, and then use ratio frequency unit CC2420 to send it, at the same time, it also receive data sent from other wireless units, and then send data to simulator via bus of RS485.In addition, some sensor circuits should be designed according to difference of demand. The MCU msp430 has rich port resources. Via these I/O ports, sensor circuits can be easily connected with MCU, and MCU is used to processes the data colleted by sensor circuits.Software development consists of two parts,The first is the development of communication protocols, Architecture of network communication protocol can be divided into 5 layers, they are application layer,application supporting layer, network layer, and media access control layer and physical layer. Physical layer and media access control layer adopt IEEE802.15.4 standard,and Network layer and application layer using ZigBee protocol Application layer process data which is transferred wirelessly and display on wireless unit such as using LCD or LED; Application supporting layer can receive data and execute command from simulator; Network layer is in charge of transferring and transmitting information; Media access control layer is on duty of point-to-point communication and security mechanism; Physical layer is on duty of the operation of bottom layer hardware equipments. Media access control layer and physical layer depend on the support of communication module and hardware driver.Another part of Software development is the preparation of the test procedure of environmental parameters Programming software using IAR Embedded workbench,and development language using C language. Test procedures include wireless receiver and wireless sending procedures and RS485 serial communication program and the test procedure of environmental parameters.Besides, in order to more easily carry out wireless transmission and control, remote control system also adds a simulator,it is in fact equivalent to a operation and control of interface of user. Wireless unit should be transparent to the simulator,and wireless communication between modules with the simulator using standard RS485 electrical standards. Through the window of the simulator, users can easily observed that the various conditions of system communication,such as a variety of communication data and control commands of receive and transmit, the settings of communication speed and parity,and the size of bit error rate and so on.Although more than a year after the experiment and test, The entire system has been basically achieved the above mentioned functions and requirements, it need further improvement in a number of issues,such that wireless speed communication and communication distance did not achieve the desired results, simulator functions need to keep improving, and data security and communication efficiency of communication also need to be further improved.