PCB Blog - Design of PCB board remote Fault Diagnosis System

This paper introduces a PC-based serial port test system for PCB board remote fault diagnosis, which has the characteristics of advanced design, concise structure, powerful functions, high cost performance, and easy portability. The use shows that the proposed design scheme is feasible.

1. System overall structure design
The PC generates the detection control command of each step according to the detection process file, and sends the control command to the single-chip testing system through the RS-232C serial interface; receives the measurement results sent by the single-chip testing system when the detection is completed, processes the data, and gives the fault. Diagnosis conclusion, display the detection result of the PCB board in the display window of the system soft panel (operation interface); control the entire detection and diagnosis process of the PCB board. The system can be connected to the network through network interface equipment to form an intelligent remote fault diagnosis system with network functions, or further evolve into a remote measurement and control system or a remote management system to carry out wired/wireless channel remote data communication to realize the digitalization of the measurement and control system. Networked and intelligent. The networking of the system breaks the geographical and quantitative boundaries of the deployment area and equipment expansion to a certain extent, and realizes the sharing of hardware and software resources, tasks and loads of the entire network system.

The single-chip measurement and control instrument system is mainly composed of AT89C52 single-chip microcomputer, serial communication module, frequency measurement and counting module, voltage measurement module and channel control circuit of the program-controlled switch matrix, etc. It realizes serial communication, measures frequency, voltage, count, and generates signal switching module. control signal. The sampling/receiver completes the level conversion, signal conditioning and sampling of the measured signal under the control of the single-chip microcomputer, and provides input signals for the measurement circuit of the single-chip measurement and control instrument system. The excitation signal source is an excitation signal generating circuit under the control of the single-chip microcomputer, which provides the required working power or excitation signal for the measured object plugged into the external socket. The programmable switch matrix is the input/output channel of the excitation signal/response signal. It completes the program-controlled switching of the excitation signal of each pin of the external socket, adds the power supply and excitation signal required by the pin, and responds to the frequency or voltage output by the pin. signal out. The 24-pin external socket is the interface between the measured object and the single-chip measurement and control instrument system, and is used to install the 24-pin general PCB board to be tested. The manual test probe completes the signal level sampling of special observation points in the PCB board, and can also input excitation signals according to actual needs to realize manual fault finding.

The serial communication module adopts zero MODEM connection to realize short-range communication with a transmission distance of less than 15m, and provides input/output channels for the transmission of control commands from PC and measurement data of the single-chip test system. The main control software of the system is composed of PC measurement and control software and single-chip test software. Among them, the PC measurement and control software is written in the Windows environment using the language Microsoft Visual Basic 6.0, and the single-chip test software is written in the MCS-5l assembly language. The flow chart as shown in picture 2. The main functions realized by the system are system self-check (including power-on self-check and key-press self-check), automatic diagnosis and manual diagnosis. The use shows that the system has stable performance, reliable operation, friendly man-machine interface, simple operation and maintenance, and realizes portability. It has obvious application advantages and broad development prospects. The system has passed the technical appraisal of the relevant unit organization. The PCB board remote fault diagnosis system adopts the design scheme of serial port test system based on PC, which has the characteristics of advanced design, concise structure, powerful function and high cost performance, and has good reference value for other similar applications.