The Realization Of The Remote Controller Of The Electric Water Heater In Sopc Design

The subject described in this paper is part work of the project Controller for Electrical Home Heater entrusted by Zhongshan Kitchen Device Factory in Guangdong. Besides the basic requirements of a usual home heater like safety and auto-control on water temperature in tank, the new one was supposed to have more functions, the most important ones of which are temperature control on outlet and remote-switch on/off the machine. The former function is realized by controlling a small DC motor. The rotation of the motor is controlled according to the temperature of the outlet, the changing of motor's rotation changes the proportion of cold to hot water to adjust the temperature to the preset value. This paper mainly deals with the latter function ie the design and realization of remote switch control. The goal is not only the current requirements for the project but also the future possibility of product upgrade. For this reason the SOPC design and realization is given in this paper.For the first goal, several possible methods are discussed technically and economically. As a result, a scheme based on BP call machine is put forward. The realization of the scheme reaches two benefits. First of all, just one MCU is used for both tasks in either remote control or all other functions. Secondly, the BP call machine is used in the way of plug-in and plug-out, so that it can work as either a controller or just an information machine. The key problem for this benefit is to solve POCSAG's decoder using MCU's program instead of decoding by special chip. In this way, the connection between the BP and the heater becomes simple and indepandent. The additional advantage is to reduce the cost of realization. At the other hand, the software decoder makes programming more complex and difficult. Careful work on MCU selection, multi-use of I/O ports and program optimization is done for the realization. Now the hardware debugging is finished and the whole controller works successfully.The second goal is the remote control design based on SOPC. The development of PLD (programmable logic Device) is making the price tending to applications of consumer products. Furthermore several kinds of 8/32 bit MCU cores are available tousers. This makes SOPC possible. The first step for this goal is to design POCSAG's decoder using VHDL which will act as a function core in the full design of heater controller. The process including compiling, synthesizing and simulation is supported by EDA tools, and at last the design is downloaded to an FPGA chip. It shows that the design works properly. Then an 8 bit MCU PicoBlaze developed by Xilinx Company is used for the further SOPC design of remote controller. The circuit structure and realization are discussed and most components are debugged successfully.