HMI-SCADA Guides Technical Guides

What is HMI?

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1. What is HMI?

The Human Machine Interface (HMI) means the device that communicates between the operator and the equipment. Strictly speaking, any way a person “communicates” with a machine through an interface screen is an HMI.
HMI monitors are now so familiar to people, especially in industry, it plays an extremely important role in the communication between people and machines. So what is the application of HMI? I will present basic and specific about HMI for new students to understand the concept, from which it applies well to the job.

The sensor on your microwave is an HMI, the control system on the washing machine, the remote control software selection guide on the TV are all HMI, so it can be said that touch phones are now devices. HMI in the broadest sense. We can write applications directly on the phone, or iPad, tablet to control industrial equipment.

2. HMI Classification

2.1 Traditional HMI devices:

Traditional HMI includes:

+ Information input device: switches, buttons, etc.

+ Information output devices: indicator lights, horn, gauges, paper recorders, etc.

– Disadvantages of traditional HMI:

+ Incomplete information.

+ Incorrect information.

+ Limited information storage capacity.

+ Reliability and low stability.

+ For large and complex systems: the complexity is very high and it is difficult to expand.

2.2 Modern HMI devices:

Due to the development of Information Technology and Microelectronics Technology, HMI today uses powerful computing devices.

Modern HMI is divided into 2 main types:

+ HMI on PC and Windows / MAC platforms: SCADA, Citect, etc

+ Embedded HMI: Dedicated HMI, operating system is Windows CE 6.0 or a separate operating system

+ There are also a number of different HMI variants MobileHMI using Palm, PoketPC.

– Advantages of modern HMI:

+ Timeliness and accuracy of information.

+ Flexibility, easy to change and change the necessary information.

+ Simplicity of the system, easy to expand, easy to operate and repair.

+ Features “Open”: strong connectivity, connecting many types of devices and many types of protocols.

+ High storage capacity and long lasting

– Position of HMI in modern automation system:

HMI is always present in modern SCADA systems, the position of HMI at the control and supervision level:

3. Structure and operating principle of HMI

3.1 Structure of HMI:

– Hardware :

+ The display screen

+ Touch panel (HMI type with common touch panel with display)

+ The keys are


+ Program memory: ROM, RAM, EPROM, Memory card, etc

– Software:

+ The object

+ Functions and commands

+ Software development

+ HMI construction tools

+ Tools for connecting, loading programs, and troubleshooting

+ The simulation tool

– Communication:

+ Communication ports: RS232, RS485, Ethernet, USB

+ Communication protocols: Mobus, CANbus, PPI, MPI, Profibus, Ethernet/IP, etc

3.2 How does HMI work?

HMI is the operating interface between person and machine via PLC, they are connected with each other by signal cable. When the operator pushes the button on the screen or sets the parameters, the request will be sent to the PLC, PLC controlling the line machine.
In contrast, the chain system can send the operating status or current parameters to the HMI screen via PLC to help people perform the monitoring and control process.

4. HMI specifications

+ Display: LCD / LED

+ Screen size: 3.5”, 5.6”, 10”, 15” …

+ Screen resolution: VGA, SVGA, XGA …

+ Operation interface: touch, keys

+ Power supply: AC / DC

+ Program memory capacity, data memory, Flash data: decide the maximum number of variables, the number of screens and information storage capacity such as history data, recipe, images, backup …

+ Standard communications, support protocols: RS242 / RS485 / Enthernet / Modbus …

+ Number of objects and commands supported by HMI

+ Expansion ports: Printer, USB, CF card, SD card …

5. Process of building HMI system

– Hardware selection:

+ Select screen size: based on the number of parameters / sensor information displayed simultaneously. demand for graphs and graphics.

+ Select the number of hard keys, the maximum number of touch keys to use at the same time.

+ Select expansion ports if there is a need for printing, reading bar codes, connecting other peripherals.

+ Selecting memory capacity: according to the number of parameters to be collected, data storage, number of screen pages to display.

– Build interface:

+ Hardware configuration: select hardware (Model), connected device (PLC), protocol standard …

+ Build screen screen pages.

+ Assign variables (tags) to objects.

+ Use special objects.

+ Write script programs (optional).

+ Simulate and troubleshoot the program.

+ Load the device into the HMI.

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