Understanding basic human-machine interface (HMI) knowledge is essential for beginners. HMI products consist of both hardware and software. The hardware includes a processor, display unit, input unit, communication interface, and data storage unit. HMI software generally comprises two parts: system software running on the HMI hardware and screen configuration software running on a PC with a Windows operating system. Below, we will introduce 10 essential basic facts about HMIs.
1. Basic functions and selection criteria of human-computer interface products
Basic functions:
Equipment operating status display, such as indicator lights, buttons, text, graphics, curves, etc.;
Data and text input operations, and printing output;
Production formula storage and equipment production data recording;
Simple logic and numerical operations;
Connect multiple industrial control devices to form a network.
Selection criteria:
Display screen size, color, and resolution;
HMI's processor speed performance;
Input method:
Touchscreen or membrane keyboard;
For screen storage capacity, note whether the manufacturer specifies the unit of capacity as bytes or bits.
The type and number of communication ports, and whether printing functionality is supported.
2. Classification of Human-Computer Interfaces
HMIs with membrane key input: display size less than 5.7', free screen configuration software, considered entry-level products. Examples include the POP-HMI small human-machine interface.
Touchscreen input HMI: The display size is 5.7' to 12.1', the screen configuration software is free, and it belongs to the mid-range product category;
High-performance HMI based on tablet PCs with multiple communication ports: display size greater than 10.4', screen configuration software is chargeable, belonging to high-end products.
3. The difference between a human-computer interface and a commonly referred to "touchscreen".
Strictly speaking, there is a fundamental difference between the two. A "touchscreen" is merely a hardware component that may be used in human-computer interface products; it is an input device installed in front of the display screen that replaces some functions of a mouse and keyboard.
Human-machine interface (HMI ) products are devices that combine hardware and software for human-computer interaction. In industry, HMI products with touch input capabilities are often referred to as "touchscreens," but this is inaccurate.
4. The difference between human-machine interface and configuration software
Human-machine interface 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 main type of device they connect to is a PLC.
Configuration software is a general-purpose tool software product that runs on a PC hardware platform and Windows operating system. It can also be used together 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, modules, etc. Moreover, due to the powerful performance of the PC hardware platform (mainly reflected in speed and storage capacity), the functions of general-purpose configuration software are also much stronger, making it suitable for large-scale monitoring systems.
5. Does the human-machine interface product include 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.
6. Can the HMI 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.
7. The human-machine interface can only be accessed via a standard serial communication port.
Does it connect to other devices?
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. Does the device have communication capabilities?
Connecting with human-machine interface products?
That should be the case. Because general-purpose human-machine interface (HMI) products offer a large number of readily available and commonly used device communication drivers; typically, simply selecting the corresponding communication driver for the connected device in the HMI's screen configuration software is sufficient to establish a communication connection between the HMI and the device.
If the configuration software of the selected HMI product 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, and ask the HMI manufacturer to develop a communication driver for the device.
9. Can the PC with a display screen communicate directly with the PLC?
How to complete the HMI functionality?
Of course, you can. However, you'll need to develop the corresponding configuration software for the PC to become a true HMI product.
10. What are the future development trends of human-computer interfaces?
With the development of digital circuits and computer technology, the distinction between high, medium and low functionality in future human-machine interface products will become less and less obvious, and the functions of HMIs will become richer and richer; HMI products with an inch or larger will all be color displays, and the lifespan of the screens will also be longer.
Due to the decreasing cost of computer hardware, HMI products will primarily feature high-end tablet PCs as their hardware. 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 size less than 5.7 inches), with their advantages in size and price, will find widespread application in human-computer interaction for small mechanical devices as their functionality is further enhanced (such as by adding I/O capabilities).
