The Design And Implementation Of Cold Storage Controller

This paper takes the "Cold Storage Automatic Controller GC1719" for the "Dalian Bingshan Jiade Automation Co., Ltd." as the application background and a high-performance but low-cost cold storage control system is developed. To be compatible with the legacy and keep the advantage of the last control system, the new solution based on the last one is proposed.The hardware circuit comes from the design of the last system "GC1711", including the ATmega 128 for the processor, 7LB176 for the RS485 circuit, DM7407 for the relays output and the constant-current thermal resistance system for temperature measurement. The cold storage temperature control owns the features of great inertia and low accuracy, so the simple but effective control system, bang-bang system, is used. The defrosting which can improve the cooling performance is an essential link of the cold storage control system, and the strategy of the cycle defrosting is the common one. The key point is to control the operation sequence and opportunity of the equipments in order to avoid the effect within the equipments and the grid pollution due to the high-power equipment operation. The project gets the thought from the extreme programming, so the programming for monitoring exceeds the one for the control system and touches the goal through the iteration by the development phases. The monitoring system is based on the MODBUS protocol between the PC serial port and the controller's. According to the master-slave communication features, the "Blocking Objects" of the operation system are invited to the asynchronous communication for the monitoring programming in order to improve the efficiency of the testing software. The real-time multi-task processing is the fundamental character and it is easy to implement for the embedded operation system. But for the 8-bit MCU, the operation system can not be installed, so the task division should be realized at the programming design level. By means of the theory and analyze tools of the finite state automata, the paper proposes a simple framework for the modular design of the control task as well.Finally, this solution and implementation scheme is demonstrated to be reasonable. The products with the idea of the paper have been put into the industry application for about one year, the positive evaluation from the customers is more than the negative and they approve the maturity and expansibility of the controller.