What exactly is the hardware inside of an HMI?

sparkie

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I'm curious what the hardware inside of an hmi is. From what I gather it seems the hmi is a small computer that you build an interface on to send, receive and display data to a plc. It has its own os and doesn't directly process data.
 
While you are right in general (and mostly about very low priced HMIs) some HMI programs are very flexible in handling alarms. logging data and sending information from one port to another including email. This could be called 'processing data'
 
They are simply a motherboard with some kind of microprocessor which could be an x86 (intel) based, ARM, Atmel, etc. They run some sort of operating system, whether it is proprietary, Linux, or a flavor of Windows. Most of them you cannot easily tell because it silently boots, even Windows Embedded can silently boot to not be able to see what the OS is. The key to them all is the software that runs the HMI and handles the communications.

I run AdvancedHMI software on Panel PCs with either Windows or Linux. I can configure the screen to boot up without showing any of the signs of a typical OS boot up. It still consists of the processor, OS, and software.
 
So when you purchase a new hmi does it have an os or do you install one? Also, would something like factorytalk me fill the same role as advanced hmi?
 
If you are talking about a PC based HMI, such as AdvancedHMI, RSView, or Indusoft, etc., then you could buy a panel PC without an OS and load Windows yourself. But if you are talking about a hardware based HMI, such as as PanelView or Red Lion, then it always comes with an OS loaded in firmware.

Hardware based HMIs generally use a custom designed "motherboard", a special OS and software designed only for that hardware. This is where PC Based/Open HMI software has a huge advantage. If you are using brand A panel PC and 5 years later it goes bad and is obsolete, then it is easy to replace it with brand B panel PC. While hardware based HMIs have you locked into that particular piece of hardware.
 
What makes me think is that the comm ports of an HMI are very versatile. In most HMIs the same port can be configured as RS232, RS485, Modbus, DF1, Dh485 and so on. The same applies for the Ethernet ports. As the hardware is the same, it means that the port use the protocol dictaded by the software settings.
Why doesnt this happen with PLCs too? Is it a buissiness decision or a hardware restriction?
 
grnick50 said:
In most HMIs the same port can be configured as RS232, RS485, Modbus, DF1, Dh485 and so on.
Click to expand...
RS232 versus RS485 is a hardware difference. Modbus versus DF1 are software differences. Theoretically any PLC with a RS232 or RS485 port could support both DF1 and Modbus, or any other serial based protocol.
grnick50 said:
The same applies for the Ethernet ports. As the hardware is the same, it means that the port use the protocol dictated by the software settings.
Why doesnt this happen with PLCs too? Is it a business decision or a hardware restriction?
Click to expand...
For the most part Ethernet ports are the same, so yes, any PLC with an Ethernet port could support all of the Ethernet protocols such as ModbusTCP and Ethernet/IP. There are a few exceptions, such as an EtherCAT slave, which does require a special ASIC behind the Ethernet port making it a hardware difference.
 
For the most part it is business decision...regardless of software or hardware limitations.

The PLC makers put proprietary communications on their equipment to entice you to use more of their equipment since it will accept the communications without issue.
 
Thanks for all the info guys. I'm starting to expand into HMI territory. If anyone has anything to add I'm still listening
 
Something I missed, the data processing, modern HMI's are getting quite good at this. You can create graphs and trend lines, manage multiple forms of communication (Red Lion is good at that), and even do some process control.

The HMI is no longer just a data repeater and place to put buttons you don't want to hard wire they are increasingly working hand in hand with the rest of the control system. When I am writing a program I stop and think is it easier to have the PLC do a certain function or the HMI take care of it.
 
Free software

Automation direct has a free software for HMI with simulate function if you want to play with a HMI. It is called
" C-More micro" software
 
Thanks guys. It's a really broad array of equipment and I can see that you make a choice based on needs and budget.
 
sparkie - functionality is more important for me and great software. The other issue is life expectancy of the HMI - I could tell you about many big brands that fail regularly - no names - have not had an Omron screen fail to date - many others have died in a few years - very expensive and inexpensive. Budget and needs yes - functionality and longevity more so for me and really good software. I really hate most of the HMI software around whether it be free or very expensive! Could say the same for PLC software as well - very frustrated with what is on offer - mostly clunky and hard to use - takes to long to program and make less money! Yes, I have my own business.
 
I would say that an HMI is just the software. The (horrible) term operator interface terminal OIT is hardware and software included.

The hardware is basically just a single board computer, custom built by the vendor.
In contrast, most computers are multiple boards & parts sourced from multiple vendors.

These are my reasons for using an OIT:
1. HMI in a box. software & hardware ready to go
2. IT friendly. or not needed at all.
3. Power fault ready. not even Windows embedded is immune to power loss.
4. Rock 'n roll tested. An OIT is built for harsh environments. http://www.halthass.co.nz/reliability-services/halt-testing-new-zealand/halt-highly-accelerated-life-testing/attachment/halt-chamber-slow-motion-toyo-jp-2/
5. Built for a long life. Made to last in the field and available for sale for many years (10+)

Yes, once you use an OIT you are locked in to the same vendor and compatible model. But if those 5 above are what you need, use an OIT.
 
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