1. Introduction
Currently, most industrial production equipment in China is operated and inspected manually online, which suffers from significant drawbacks such as high cost, low efficiency, and substantial safety hazards. Addressing the current state and urgent needs of domestic industrial production, a PLC touchscreen control system based on an embedded system has been developed. This system enables online remote monitoring and control of operating equipment, reducing labor costs and safety risks while improving operational efficiency and production effectiveness. The touchscreen in this system provides both real-time display and online control functions, allowing a single system to perform both equipment monitoring and control tasks.
2. System Main Framework
This system mainly consists of two parts: an embedded system and a touch screen. The PLC connected to the touch screen is controlled by the touch screen, as shown in Figure 1.
Figure 1 PLC Touch Screen Control System
1) Embedded systems are used to control the entire system, including the control of communication interfaces, display interfaces, and low-level hardware drivers.
2) The touch screen display is used to display the status of slave operating devices and remotely control them. Its display interface is realized through dynamic display by configuration software. The interface is simple, intuitive and easy to operate.
A PLC touchscreen control system can be divided into hardware and software components. The hardware component mainly includes an embedded processor, power supply module, RS485 interface, touchscreen interface circuit, USB interface circuit, serial communication module, touchscreen, and PLC. The software component mainly includes program development tools, program simulation and debugging software, and program design.
3. System Hardware Design
3.1 System Hardware Structure
The overall hardware structure of the system is shown in Figure 2.
Figure 2 Hardware structure of PLC touch screen control system
The system processor uses Samsung's S3C2416 chip, a 16-bit/32-bit ARM926EJ reduced instruction set processor designed by ARM. It has excellent core performance and provides a complete set of commonly used system peripherals, minimizing overall system overhead and eliminating the need for additional components. It has rich peripherals, a maximum clock speed of 533MHz, and four power control modes. It features low power consumption, high performance, and fast response, making it very suitable for handheld devices.
3.2 Touchscreen Display Section
The system uses a 7-inch touchscreen for display. The display interface utilizes the dynamic display of MCGS configuration software. Before using the configuration software, BootLoDer settings need to be configured to specify the system's hardware configuration and set some communication parameters, including the touchscreen model, PLC model, specify the system's read and write areas, the touchscreen MPI address, and the transmission frame length.
3.3 Communication Method
The communication method adopts RS485 serial communication, which has the advantages of strong anti-interference ability and long transmission distance, with a maximum communication distance of up to 1200M, making it very suitable for industrial control sites.
4. System software development environment
4.1 Programming and Debugging Based on ADS
The software programming for this system was done using ADS software. ADS (ARM Development Loper Suite) is developed by MetRowerkS and is the primary development tool for ARM processors, as well as the most mature ARM development tool currently available.
4.2 Program Debugging Based on AXD
ADS software has an online debugging function. Program debugging requires the AXD tool under ADS software, and H-JtAG is needed to debug the experimental board. Before using H-JtAG, its configuration file needs to be added. After completing the above steps, open the agent debugging software H-JtAGServeR, select CPU, and you can successfully connect to the experimental board. You can see the program running on the experimental board, and verify and modify the program based on the phenomena until the program meets the design requirements.
5. System Design and Operation Flow Implementation
After the system software design and debugging are completed, the modules are combined and the whole machine is tested. Once this is done, the entire system can be put into operation.
5.1 System Design Technical Roadmap
The system design technical roadmap is shown in Figure 3. The system design follows a top-down, modular approach to facilitate overall coordination and functional debugging.
Figure 3 System Design Technical Roadmap
5.2 System Operation Flow
The system operation flow is shown in Figure 4. After power-on, the system first initializes, then detects the current working status of the PLC and displays it on the touch screen. After that, it waits and judges whether there is a control command input. If not, it continues to display the current status. Once a control command is input, it executes the control operation and displays the status after the operation on the touch screen, thus realizing the dual function of real-time detection and control of the system.
Figure 4 System Operation Flow
6. Experimental Results and Analysis
To verify the system's performance, an experimental platform was built for testing, including a configuration program written using MCGS configuration software and a Siemens S7-200 PLC.
MCGS configuration software is a Windows platform-based configuration software system used for quickly constructing and generating host computer monitoring systems. This experiment uses MCGS 7.6 embedded version configuration software combined with a PLC touchscreen to develop a configuration monitoring system that collects and monitors the system's operating status in real time, controlling system operation.
The Siemens S7-200 series PLC was selected. The S7-200 is a small programmable logic controller suitable for automation of detection, monitoring, and control in various industries and applications. It features extremely high reliability, a rich instruction set, abundant built-in integrated functions, powerful communication capabilities, and a wide range of expansion modules, making it very suitable for this solution.
Figure 5 Touchscreen configuration display interface
Figure 5 shows the display and control interface of the touch screen. Utilizing the dynamic display of the configuration software, the interface is simple, user-friendly, and easy to operate. The current operating status of the system can be intuitively viewed from this interface, and the PLC can be controlled in real time by pressing the control buttons on the interface. Figure 6 shows the PLC's working status display. The relative values displayed on the interface show the current distance of the motor relative to the origin of the X-axis and Y-axis tracks. The start and end buttons are used to control the motor's movement. When the start button in the first row is pressed, the PLC's Q0.0 pin is activated, the corresponding LED is lit, and the motor moves to the X-axis start point. When the end button in the first row is pressed, the PLC's Q0.1 pin is activated, the corresponding LED is lit, and the motor moves to the X-axis end point. The operation of the Y-axis in the second row is the same as in the first row. Experimental results demonstrate that the touch screen can communicate normally with the PLC, realizing the display and control of the working status of the motor connected to the PLC, meeting the design requirements of this system, and the system design is successful.
Figure 6 shows the working status of the PLC controlled by the touch screen.
7. Conclusion
A PLC touchscreen industrial control system based on an embedded system was designed and implemented. This system enables online monitoring and real-time control of subordinate industrial equipment, improving production efficiency, reducing production costs, and mitigating safety hazards in industrial settings. It holds significant importance for the field of industrial control and has broad application prospects.
