The Controller Design Of LNG Dispenser Based On PIC Microcontroller

With the acceleration of the process of China’s modernization, the automotive industry has been rapid development, Vehicle refilling machinecar as an essential tool, has already been widely appreciated. Compressed Natural Gas(CNG) dispenser is now used in many cities, with the growing concern of environmental issues, Liquefied Natural Gas(LNG) gradually moved into the line of sight of the people, it is not only environmental protection than CNG, but also has a great advantage in security and economic aspects. Therefore, the study of LNG dispenser is the development direction of the filling machine system’s design.Based on LNG dispenser’s design requirements, with reference to the design specifications and standards of CNG dispenser, this article completed LNG dispenser controller system design which is based on PIC microcontroller.The paper aimed at dispenser control system’s functional requirements, proposed the overall design scheme of the control system, the main function includes multi-channel data acquisition, signal processing, the output liquid refrigeration control, the keyboard operation, the display of the refilling information, communication with the host computer, and so on. Under the proposed program, we have given the rational design of hardware circuit and software programs of the LNG dispenser control system. At the same time, we tested the system hardware and software, verified the correctness and reliability of the control system.This paper first describes the selection of the system devices, controller utilizes8-bit low-power PIC microcontroller; flowmeter choose high-precision, ultra-low temperature83F mass flowmeter. The communication between the mass flowmeter and the microcontroller adopts MAX485interface. Secondly this paper focused on the design of the hardware system, elaborated the circuit design of each module, the part of the hardware involves MAX485interface circuit, I/ V conversion circuit, keyboard and display module interface circuit and the clock circuit. Finally, based on the hardware design, we gave the software design process and the implementation code, and debugged part of the software, verified the correctness and reliability of the software programs.