I. Introduction to HMI
HMI is an abbreviation for Human Machine Interface, also known as a human-computer interface. A human-computer interface (also called a user interface or user interface) is the medium through which a system and a user interact and exchange information. It converts information from its internal form to a form that is acceptable to humans. Human-computer interfaces exist in any field involving human-computer information exchange.
II. Types of HMI Interfaces
HMIs have many types of interfaces, including RS232, RS485, CAN, and RJ45 network cable interfaces.
For example, in a factory, we need to collect information such as temperature, humidity, and machine status in various areas. A main controller monitors and records these parameters and can handle unexpected situations. This is a typical application of SCADA/HMI.
Generally speaking, an HMI system must have several basic capabilities:
Real-time data trend display – instantly display the captured data on the screen.
Automatic data recording – Data is automatically stored in the database for future viewing.
Historical data trend display – visualizing data from the database.
Report generation and printing – This function converts data into report formats and allows for printing.
Graphical interface control – Operators can directly control machines and other devices through a graphical interface.
Alarm generation and logging – Users can define conditions for alarm generation, such as excessive temperature or pressure exceeding a critical value. Under such conditions, the system will generate an alarm to notify the operator to handle the situation.
III. Composition and Working Principle of HMI (Human Machine Interface) Products
Human-Machine Interface ( HMI) products consist of two parts: hardware and software. The hardware includes a processor, display unit, input unit, communication interface, and data storage unit. The processor's performance determines the overall performance of the HMI product and is its core component. Depending on the product level, 8-bit, 16-bit, or 32-bit processors can be selected. HMI software generally consists of two parts: system software running on the HMI hardware and screen configuration software running on a PC with a Windows operating system. Users must first create a "project file" using the HMI's screen configuration software, and then download the created "project file" to the HMI's processor for execution via the serial communication port between the PC and the HMI product.
IV. Basic Functions of HMI (Human Machine Interface) Products
1) Equipment operating status display;
2) Data and text input operations, and printing output;
3) Production formula storage and equipment production data recording;
4) Simple logic and numerical operations;
5) It can connect to a network of various industrial control devices.
V. Selection Criteria for HMI (Human Machine Interface) Products
1) Display screen size, color, and resolution;
2) HMI processor speed performance;
3) Input method: Touchscreen or membrane keyboard;
4) Screen storage capacity: Note whether the manufacturer specifies the unit of capacity as bytes or bits;
5) Types and number of communication ports, and whether printing function is supported.
VI. Eight Key Concepts of Human-Machine Interface (HMI)
1. Can a human-machine interface only connect to a PLC?
That's not the case. Human-machine interface (HMI ) products were developed to solve the human-machine interaction problem of PLCs. However, with the development of computer technology and digital circuit technology, many industrial control devices have serial communication capabilities. Therefore, any industrial control device with serial communication capabilities, such as frequency converters, DC speed controllers, temperature controllers, and data acquisition modules, can be connected to HMI products to achieve human-machine interaction functions.
2. What is the difference between a human-computer interface and what people commonly refer to as a "touchscreen"?
Strictly speaking, there is a fundamental difference between the two. A "touchscreen" is merely a hardware component that may be used in a human-machine interface (HMI) product; it's an input device installed in front of the display screen, replacing some functions of a mouse and keyboard. A HMI product, on the other hand, is a human-computer interaction device that includes both hardware and software. In industry, people often refer to HMI products with touch input capabilities as "touchscreens," but this is inaccurate.
3. Does the human-machine interface product have an operating system?
Every human-machine interface (HMI) product has a system software component. This system software runs on the HMI's processor, supports multitasking, and requires a small operating system to manage the system software. High-performance HMI products based on tablet computers typically use common embedded operating systems such as WinCE and Linux.
4. What is the difference between human-machine interface and configuration software?
Human-machine interface (HMI) products, often referred to as "touchscreens," consist of HMI hardware and corresponding dedicated screen configuration software. Generally, different manufacturers use different screen configuration software for their HMI hardware, and the primary device they connect to is a PLC. The configuration software, on the other hand, is a general-purpose utility software product that runs on a PC hardware platform and the Windows operating system. It can also be used with a PC or industrial control computer to form an HMI product. General-purpose configuration software supports a wide variety of devices, such as various PLCs, PC boards, instruments, frequency converters, and modules. Furthermore, due to the powerful performance of the PC hardware platform (primarily reflected in speed and storage capacity), general-purpose configuration software offers much more powerful functionality, making it suitable for large-scale monitoring systems.
5. Does a device with communication capabilities necessarily connect to a human-machine interface product?
That should be the case. Because general-purpose HMI products offer a large number of readily available communication drivers for commonly used devices; typically, simply selecting the corresponding communication driver for the connected device in the HMI's configuration software is sufficient to establish a communication connection between the HMI and the device. If the selected HMI product's configuration software does not have a communication driver for the device to be connected, the user can inform the HMI product manufacturer of the communication port type and protocol of the device to be connected, requesting the HMI manufacturer to develop a communication driver for that device.
6. Can a PC with a touch screen communicate directly with a PLC to perform HMI functions?
Of course you can. However, you'll need to develop the corresponding HMI software to make the PC a true HMI product.
7. Can the human-machine interface only be connected to other devices through a standard serial communication port?
This is true in most cases. However, with the development of computer and digital circuit technology, the interface capabilities of human-machine interface products are becoming increasingly powerful. In addition to traditional serial (RS232, RS422/RS485) communication interfaces, some human-machine interface products now have data interfaces such as network ports, parallel ports, and USB ports. These can be connected to industrial control equipment with interfaces such as network ports, parallel ports, and USB ports to realize human-machine interaction.
8. What are the future development trends of human-computer interfaces?
With the development of digital circuits and computer technology, the functional distinctions between high, medium, and low-end HMI products will become increasingly blurred, and HMI functions will become increasingly rich. HMI products with screens larger than 5.7 inches will all feature color displays, and screen lifespans will be longer. Due to the decreasing cost of computer hardware, high-end HMI products will primarily utilize tablet PCs as their hardware, as these high-end products offer significant advantages in processor speed, storage capacity, the variety and number of communication interfaces, networking capabilities, and software resource sharing, representing the future direction of HMI product development. Of course, smaller-sized HMI products (display sizes less than 5.7 inches), due to their advantages in size and price, will be widely used in human-computer interaction applications for small mechanical devices as their functionality is further enhanced (such as by adding I/O functions).
