The Research And Design Of16-channel Isolated Digital Quantity Input/Output

In industrial environment, due to the motor switch, electrostatic discharge or adjacent arc strike, they often can produce up to hundreds or even thousands of volts. If there is no isolation, the voltage could damage the normal transmission of signal or cause system collapse, even cause unrecoverable damage on hardware. In the process of industrial production, a variety of instruments and equipment and other sophisticated detection equipment will be used. The transmission signals between them are both large signals which are a few kv or hundreds of ampere and small signals which are weak to millivolt or microamps. There are both low frequency dc signals and high frequency pulse signals. Therefore, after constituting a system, it is often found that mutual interference of transmission signals between the instruments and equipment can cause unstability or even wrong operation of the system. So the problem of electromagnetic interference and mutual compatibility need solving. In addition,"ground loop" cause distortion in the process of signal transmission. Use signal isolation method in each process of the loop to disconnect the loop. And the method also doesn’t affect the normal process of signal transmission. The method solves the problem of ground loop thoroughly.In view of the prevalence of interference problem in industrial application, the input/output module which is designed in this paper accomplishes signal transmission task effectively and reliably. The input/output module has used the opticalcoupler isolation, the power supply isolation, iCoupler digital isolator technology so as to realize one-way signal transmission. The signals of output can not influence the input. The input and output fully implement electrical isolation. Therefore, the input/output module has strong anti-jamming capability, work stability, long service life, and high transmission efficiency.On the basis of consulting a lot of technical literature, this paper grasps from the overall design firstly and determines the demand analysis. And then from two aspects of hardware and software, this paper tells the design process in detail. First of all, ensure the realization of the fundamental function——data transmission and acquisition, and then adopt the three isolation technology from the principle, and ensure the stability and reliability of the hardware from the PCB layout and wiring. Finally on the software, adopt instruction redundancy, software trap and watchdog to ensure the reliable operation of the program.From each chapter, introduce the content of this paper briefly. The first chapter first analyzes research background and significance of the project, then introduces interference and anti-interference technology of Microcontroller Unit application system in the industrial environment, and mainly introduces the electromagnetic anti-interference technology, finally studies the development situation of the isolated digital quantity input/output module. In the second chapter, on the basis of demand analysis, put forward overall design scheme of the16-channel isolated digital quantity input/output module. The third chapter, combining with circuit principle diagram, introduces the hardware design of main parts of the module and the design of the hardware anti-interference technology in detail. The fourth chapter, combining with the software flow chart, introduces software design of the module and the design of software anti-interference technology. The fifth chapter, first tells the program debugging, including using introduction of the module, the hardware debugging and software debugging, then summarizes and prospects the project.In this paper, the module of design supports16-channel digital quantity isolated channels. Each channel can be independently configured for input or output through software. The module of design is mainly composed of power supply, digital quantity input/output circuit, RS485, MCU, etc. For industrial application design, each part of the module has its own power supply to adopt the current isolation and not to form a ground loop. It can protect system from high transient voltage damage, and reduce the signal distortion. What’s more, it also can protect the personal safety.