How are Remote I/O and Distributed I/O Different?
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- เผยแพร่เมื่อ 21 มิ.ย. 2020
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In this video, we’re going to talk about Remote I/O and Distributed I/O. Depending on who you talk to, some say Remote I/O and Distributed I/O are the same thing and the terms are interchangeable … Not so says others.
So, who’s correct? Let’s investigate the history of the terms Remote I/O and Distributed I/O and discuss what they mean today.
Let’s go back a few decades to early computerized control. The predecessor of the DCS and the PLC was the Direct Digital Control or DDC system, only seen today in museums.
Many vendors such as Taylor Instruments, Bailey Control, and Foxboro had DDC systems that centered on a mini-computer connected to several proprietary I/O devices located at remote locations around the plant.
Today’s DCS is a control system that has a number of Distributed autonomous controllers each operating a number of continuous operations. The controllers are tied together via a centralized supervisory controller.
We’ve already used the terms Remote and Distributed in the context of locations of both I/O and controllers. It’s easy to see how the terms can be misunderstood.
OK. Let’s have a look at Remote I/O and Distributed I/O from a PLC perspective. Remote I/O means that the I/O module is at a remote place physically located a distance from the control PLC.
As we mentioned earlier Remote I/O is sometimes also referred to as Distributed I/O. Let’s look at a definition for Distributed I/O that differentiates it from Remote I/O.
Generally speaking, Distributed I/O has a brain or some computing capacity. By default, it is Remote.
Allen-Bradley has FLEX I/O which is a modular I/O system for distributed applications. The Flex I/O allows for the connection of up to eight I/O modules and transfers I/O data to and from a central controller or PLC.
Flex I/O is an example of Distributed I/O and the eight modules connected to the Flex I/O are examples of Remote I/O.
Siemens has the ET 200SP series of Distributed I/O that can connect up to 16 channels of digital or analog I/O with a single-wire connection.
The ET 200SP is an example of Distributed I/O and is connected to the bus system via an interface module. This system is very flexible as it can accommodate either PROFINET interface modules or PROFIBUS interface modules.
As we said earlier, Remote I/O is at a remote place physically located a distance from a control PLC. Remote I/O does not have a brain and is not capable of any computing function at all.
It’s likely safe to say that when you hear the term Remote I/O there is only one controller, or PLC, involved as opposed to Distributed I/O which has multiple controllers.
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You might want to review 2 of our other articles:
1) What is Remote I/O? (realpars.com/remote-io/)
2) What is DCS? (realpars.com/dcs)
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I've learned from your channel more than my whole studying in college . Can't thank you enough 🥰
That's an amazing compliment - thank you, Saleh!
Thank you for giving such type of industrial knowledge without any cost.
Lakhs of people visits your channel and read and understand through your best visual explanation.
Thank you, Devanand! We appreciate your support!
THIS channel REALLY helps to learn future automation
Amazing! Thanks for your comment!
i really appreciate the way you explained in your videos, may be in the future, you should also think about how to translate it in several language, so then it's can also help more people to understand many thing
Hi David,
Thanks for your comment and for sharing your support with us!
We currently only provide our course videos in English, but I will happily pass your feedback on to our team.
Thanks for sharing and happy learning!
I have a distributive control system. One thing i wanted to do was to operate inndegraded mode, where operation could continue in a degraded mode if a remote unit was offline.
The question would be how to write the software so that this could be done. Asked main plc vendors and did not get an answer..
You doing great job for people @RealPars
Thank you, Lukasz!
These videos are awesome. Keep up the good work guys 👌
Glad you like them! Thank you for sharing
Thanks for the simple and understandable explanation
You are very welcome!
Thank You RealPars!!!
You are very welcome, Mohammed!
I have a farm in southern california. I use automation direct plc to control my irrigation. I met a couple of electricians who remotely controlled the irrigation of a golf course with automation direct plcs. Similarly i meet a board layout engineer who set up a seimens plc unit to control credit card punching operation.
Most vendors look down on these ventures, but i think that this is a growth oportunity, especially in these times. Remember sabre tooth lion did mot survive when large prey animals went away.
Nothing wrong with Automation Direct for a simple system like that, but I would not trust them with a factory that costs tens of thousands of dollars per minute for down time, or would lose a 100 million dollars of oh say Beer that is in process like AB inbev has at any one moment. Nor where large data aquisition and MES SCADA systems are required. Try to do a totalizer in Automation Direct vs, Control Logix. the AD will not be very accurate.
thanks a lot for sharing important information
You are very welcome, Kareem! Happy learning!
Thank you guys!
Our pleasure, Marlon!
Wow man that is minor difference but very imp. Nicely explained again
Thank you, Shubham!
Hello, please share video on how fibre optic cable is used to transmit digital and analog signals and about the signal strength against distance.
Hi Shalini!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
sir, I am learning from this channel a lot ,
sir I am a student of Engineering(Electrical)
I want to know that which software you using for this type of great animated explaining
for my presentations
please sir tell me ,its will be helpful to me
Hi there,
Thanks for your comment and for sharing your support with us!
I am actually not sure about this, as this is done by our graphic and animation department.
Sorry about that!
Good explanation, but I think distributed I/O's mostly in PRO models are am right.
Thank you very much !
You're very welcome!
Great vid thanks for sharing. 🐵
What computing or processing can be enjoyed in the ET200 "distributed" I/O?
Thank you for your question. The ET200 is a family of Siemens I/O modules that communicate with the main PLC CPU via cable. One advantage is that you can place the I/O modules near your physical I/O and monitor the signals directly next to your devices. The ET200 line dates back to the Siemens Simatic S5 from the 1980s, and, as mentioned in our video, these modules do not have an embedded CPU.
However, with new technologies, Siemens has added more processing power and enhanced communication to the ET200 series, such as in the ET200SP. "ET" stands for Electronic Terminator.
Here is a link to help with your learning: Documentation for SIMATIC Controller. support.industry.siemens.com/cs/document/109744173/documentation-for-simatic-controller?dti=0&lc=en-WW
This resource contains comprehensive information about current Siemens PLCs and other components.
let’s say I want to adjust the speed of a 3ph Induction motor. So, to do that, do I still have to use the distributed I/O system even if I have Sinamics G120 CU240S drive with me? Please let me know ASAP because I’m using Simatic Manager and I’m confused with the difference between Sinamics G120 CU240S drive and Simatic ET 200S FC.
The G120 CU240S drive is a standalone VFD control unit that is connected to a G120 power unit to provide control of small motors (~4kW). The ET200S FC is a rack-connected frequency converter (also up to 4kW) that integrates its I/O into the rack communication interface. The standalone G120 version requires its own Profibus connection to the network since it is its own node.
@@realpars so ET200S FC will be used only if I want to control large motors?
I see a lot of remote IO but not distributed IO. In what circumstances would distributed IO be preferred? The only thing I can think of is an immediate action. The PLC takes some time to scan all the inputs and then run through the logic program, so a field device would shave some milliseconds if it performed some of its own decision-making. In my experience, PLCs are plenty fast though.
Great video
Remote I/O is very common in both DCS and PLC systems. This allows I/O interfaces to be placed closer to where the devices are in the field. Distributed I/O is most commonly used with instrument busses, such as ProfibusPA, ASi, and Foundation Fieldbus. These are field-level protocols which are wired and configured as nodes on a bus system, not as individual connections to an input or output card. Passive connection blocks (or bricks) can be used to simplify cabling, but the path from device to the controller is directly back through a communication card that speaks directly to the CPU.
@@realpars - OK, thanks, that's a pretty good explanation. It sounds like the advantage is that having your IO devices on a bus network may at times provide savings on installed wiring and such.
I try to find your app but it’s not available on my country , so sad, even I change the location on my store to The USA but still can’t find
Hi Mai,
Thanks for your comment!
We have recently optimized our learning platform which includes some highly requested features. As a result we had to decide to no longer support the RealPars App. You can use our webpage to continue watching the video courses.
I am still confused as tot he difference, since I am mostly a Rockwell guy I'll refer to what you said about Flex I/O. You said Flex I/O is distributed I/O but I see no difference in a Flex I/O rack and a 1756 Remote I/O rack, in the case of the Flex I/O the communication head does not have computing power in more than the ENBT card has in the 1756 chassis. they seem to be the same to me, and I would refer to them both as Remote I/O.
Brian, you are likely not alone in your question. This video looks at the definitions of distributed and remote I/O and the nuances between them. Very often, we use the terms interchangeably. In some systems, like the Siemens S7 system, these differences are clear between I/O subsystem types. In the Rockwell world, remote I/O used to be limited to I/O racks that were extensions of the main rack and used special extension cables to extend the main rack, thereby allowing the I/O to exchange data via the backplane. While this construct is still common, the use of Ethernet and IO Adapters is most often used. This can allow multiple PLCs to access the data via Ethernet (characteristic of distributed I/O), and for a rack of Flex I/O, the ability to hold configuration data in the card or adapter (also a characteristic of distributed I/O).
I can’t find the Realpars app on my iPhone
Any help on how to go about it please.
Hi Elijah,
We have recently optimized our learning platform which includes some highly requested features. We are happy to bring you these new improvements which will grant an even better learning experience, as a result we had to decide to no longer support the RealPars App. You can use our webpage to continue watching the video courses.
@@realpars Alright, thanks.
What was explained here are two different concepts. Remote I/O and Distributed Control.
Distributed I/O and Remote I/O are the same. But the more appropriate term to use is Remote I/O.
The term "Distributed I/O" is misleading because it confuses us with the original term "Distributed Control".
Distributed Control is a network of Control Modules (each with its own I/O modules, which in turn could be in direct or remote configuration)
I can tell you for sure there are still DDC systems still operating in the wild
There is a problem with this video Earlier you taught us ES200 is a Remote I/O module in the same playlist now you are teaching us that this is a distributed I/O. It's too much confusing
Thank you for reaching out with your question, and I appreciate your interest in our content. I apologize if my previous response caused any confusion. I want to clarify that the information I shared pertains specifically to the Siemens PLC system, and while other systems may offer similar functionalities, they may present them differently.
To simplify the explanation, let's consider the scenario of a conveyor system with a main powered CPU rack. This rack can accommodate a limited number of IO (Input/Output) boards before requiring an additional rack for more IO. For instance, if your main rack is located in a control cabinet and the first operator control panel is some distance away, running numerous wires from the main CPU rack to the panel can be costly. Here's where remote IO comes into play.
By replacing some IO cards in the main CPU rack with an Interphase module (IM) card and setting up a separate rack with a power supply, another IM, and the removed IO cards, you can connect them using PROFIBUS DP communication. Place this new rack near the operator station, reducing the need for numerous wires. This method is a cost-effective solution, as the main CPU believes all the IOs are still on the main rack.
For those using Siemens, this is achieved through the ET200 system, specifically employing an electronic terminator (ET). Siemens offers various ET200s to suit different needs. Moving on to distributed IO, you can use the ET200SP, a mini-CPU with substantial capabilities. By adding the appropriate interphase and establishing communication with the main CPU, the ET200SP can take on specific tasks related to the conveyor system. This setup allows for a more efficient distribution of tasks between the main CPU and the ET200SP, with both units treating the IOs as if they are in the main rack.
I hope this concise example provides a clearer understanding. For further details, you can refer to the Siemens site, which I've linked here for your convenience. Happy learning!
support.industry.siemens.com/cs/document/58649293/simatic-et-200sp-distributed-i-o-system?dti=0&lc=en-US