What is RS485 and How it's used in Industrial Control Systems?
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- Опубликовано: 7 июл 2024
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Today you will learn about RS 485. If you are familiar with RS232, then you may already know a little bit about it.
Just like it’s older brother RS232, RS485 is a form of serial communication. Think of RS485 as the younger, faster brother of RS232.
What made it such an advancement over RS232 was the fact that it could transmit not only a single device to device transmission, but also a communications bus to connect multiple devices at once.
The configuration and specifications of RS 485 make it faster and extend the range of data transmission.
You aren’t limited to fifty feet of cable like with RS 232. The maximum cable length for RS 485 is typically listed as 1200 meters or about 4000 feet.
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We used to instal high end Point of sale network with RS 485 cables. This is highly reliable. Terminal to terminal ( IRC) and Kitchen printers commonly used. All systems on embedded platform. Master / slave configuration and programs done.
Resistance to electrical noise isn't only because of cable shielding, but also thanks to the fact it uses a differential signal rather than a common ground, as with CAN bus. This also allows compensation against interference.
The range of the bus is higher and it can support faster speeds because of Differential Signalling. The signal sent across the bus is not referenced to ground, but to each other. The difference in signal levels between the bus wires determines a 1 or a 0. Noise if present pushes both the wires up or down in the same magnitude, thereby maintaining the difference in signal levels. USB is a faster bus partly because of differential signalling.
In fewer words, a balanced signal.
great summary, thank you.
Sadly, the USB bus until version 3.0 used a single twisted/balanced pair of wire, unlike the FireWire which used one for transmitting and one for receiving, causing significant delays and slow-downs on USB.
Thanks for the information. It left many basic questions unanswered (like what are the wiring and signals used and how are the basic protocols over RS-485 work).
Hoping to see a more in-depth video on those in future
Thanks for the suggestion and feedback! Will happily pass this on to our course developers.
Happy learning!
You can use Modbus Rtu is the most common case.
Very informative and easy to understand. Thanks.
Great!
thanks for making it so easy to understand :)
You're welcome!
Wow! This explain is very simple and easy to understand!
Great to hear! Happy learning!
Thank you, your video helps me to understand RS 232 and RS 485
You are most welcome! Great to hear that
You may need a termination resistor of 50 ohm. Avoid running the wires outside it become damaged by lightning. As a field service engineer I found that electricians are used to wire electricity a and electronic, make sure they know that black is ground and red is high in electronics. Rs485 wiring is very sensitive that way.
LO MÁS INTERESANTE QUE VI EN LOS VIDEOS DE RUclips
Gracias!
Appreciated your explanation in a very simple way. Thanks
Glad it was helpful!
Extremely helpful thank you 🙏🏼
You're very welcome! Happy learning!
Very helpful, Thank you very much Sir.
Great to hear! You are very welcome.
Nice video! Very didactic! 💯 I think the only missing thing was to mention the 2-wire o 3-wire type of RS-485 and the terminator resistors or voltage bias at each end of the network
Thanks for sharing that, Sergio!
Brushing up for an interview to go from a technician to controls engineer so thanks for all the help preparing. Fingers crossed.
Glad to hear that our course video helped! Best of luck on your interview!
How did it go for you?
@@Kazshmir so not exactly how I intended 😂. The position ended up in the air for a while. I’m current in maintenance management and enjoying it.
@@Metallizombie glad to hear you're enjoying it!
Explain very simply, thank you
Great to hear that, thanks for sharing!
Thank you RealPars for making valuable Videos.
Sir, I have one question: what is the difference between Standard & Protocol in communication? What's the role of a Protocol in data transmission?
Looking for positive response. Thank you.
Thanks for amazing explain
Happy to hear!
In the case of controlling a vfd, that also could have been achieved by a current loop.
You could have pointed out more benefits.
Ability to push firmware updates, remote configure device, receive status information etc.
Can I use RS 485 cable with DB 9 pin head, instead rs 232 cable with the same head?
You can use a DB9 connector but what do you mean by RS485 cable? Any twisted pair shielded cable can be used.
@@piratenu1 Lust night I have fixed...Thanks for help
welcome to another informative video brought to you by real pars today you will learn about rs-485 if you're familiar with rs-232 then you may already know a little bit about it if not check out our other video what is rs-232 the link will be provided below [Music] before we get started on today's video if you love our videos be sure to click the like button below then make sure to click Subscribe and the little bell to receive notifications of new real Parrs videos this way you never miss another one just like its older brother rs-232 rs-485 is a form of serial communication think of rs-485 as the younger faster brother of rs-232 what made it such an advancement over rs-232 was the fact that it could transmit not only a single device to device transmission but also a communications bus to connect multiple devices at once the configuration and specifications of rs-485 make it faster and extend the range of data transmission you aren't limited to 50 feet of cable like with rs-232 the maximum cable length for rs-485 is typically listed as 1,200 meters or about 4000 feet much like rs-232 rs-485 doesn't have an actual standard connector many times the old db9 connector is used in some applications terminal strips were used in place of a connector this helped rs-485 become a widely used and very versatile form of serial communication another advantage over rs-232 that I mentioned earlier is the number of connectable devices rs-485 can handle up to 32 connected devices rs-232 could only handle one this allowed users and manufacturing facilities to connect larger applications and whole machines with one protocol another +4 rs-485 is that it is less susceptible to noise issues Electric noise can cause all kinds of problems for electronics rs-232 reference ground to decipher the data it was transmitting this allowed for electrical noise to cause interference rs-485 avoids this issue which also allows for shielding of the cables to prevent noise you may be wondering what can I do with serial communications especially rs-485 one very common example in the automation world is remote control of VFDs or variable frequency drives many people just call them motor drives a simple network of a PLC VFD and an HMI allows remote control of motors in an industrial setting let's say you were monitoring a water pump filling a vessel you decide that the water is not filling fast enough to keep up with demand with your rs-485 network you can remotely monitor and control that pump from a control center this is possible since the HMI is connected to your PLC via rs-485 the plc is also connected to the VFD via rs-485 the PLC is programmed to monitor the level of the water in the vessel it also allows manual flow control if needed all of this allows you to speed up the VFD that controls the speed of that water pump problem solved thanks to rs-485 communications about what we now know about rs-485 it is faster and much more versatile than the older rs-232 users can utilize a longer cable up to 1200 meters or about 4,000 feet the greatest feature of rs-485 is the fact that you can connect up to 32 devices on one system rs-232 could only handle one at a time there is no standard connector for the protocol most manufacturers still utilize a db9 connector you can also still simply use a terminal strip this makes utilizing rs-485 simple all-in-all rs485 really allowed full automation possible with its ability to connect so many devices at once I truly hope this video is helpful please don't forget to check back later for more real Parrs videos make sure that you head over to real parse comm to find even more training material for all of your plc programming needs we offer many videos to assist you in learning plc programming and landing that job in the high-paying highly sought after field of automation and controls engineering go to real parse comm and subscribe to our highly effective training series now [Music]
Amazing video, thanks!
Thanks a lot!
I find this useful and until earlier today at work I had never heard of RS485, but I’ve heard of and used a RS232 Cable connection. I also maybe think 🤔 something that could of also being elaborated on in the age of where almost all if not many controllers have a Ethernet connection when and where a RS485 cable could be useful? I’m just junior programmer but do O.P.A.C. Engineering - Operation, Process, Automations Control Engineering. Wear many hats in what I’m doing from one week to next. Two weeks ago was on a RO plant water system startup at a plant site. It was SLC PLC with redundant processor chassis and all Ethernet connected to plc network switch with remote I/O’s. To connect directly to the SLC Processor while system was all online had to connect via RS232 on the SLC Card to Primary and Secondary Processor. As the Ethernet port was in use on both cards connected to network. That’s an example I can think of and recent where having my RS232 to USB on laptop Serial cable came in handy and was good to have. Such an example also could of being more in depth explained with the RS485 cable in various situations. However, still excellent video to educate and the more I now know.
Thanks for sharing your thoughts with us!
Is there a list of cables that fall under the category of RS232 and RS485 separately?
thanks, my right ear got it!
Very informative and well briefed 🌹
Great to hear that, Ahsan! Thanks for sharing.
Useful and easy to understand video, thanks
Great to hear that! Thanks a lot for sharing your positive feedback.
Practically t it is an industrial I2C communication that may work with 12/24 V without a clock (SCL) or a SDA pin. Instead of that uses A and B lines to communicate as if they would be TX or RX, but at the same time works by adresses. If I said something bad, correct me. I never knew about that type of bus before. (But the video gaved me an idea).
Thanks a lot for sharing knowledge, good job sir...💐🙏
You are very welcome! Great to hear that.
Wonderful I really enjoyed it
Great to hear hat, Mbilu!
RS-485 is more accurately described as the grown up big brother of RS-422. It’s not fair to compare it directly to RS-232. The reason RS-485 still enjoys massive usage in industrial applications is due to the range of physical layer implementations. As stated in the video it supports multi-drop as opposed to just point-to-point like RS-232. However, it can be used in full or half duplex modes. This means that a station on a RS-485 bus can simultaneously transmit and receive data at the same time.
RS-485 can be transmitted over both optical and copper physical layers. The optical implementations support dual redundant optical rings which are very robust. Both optical and copper layer repeaters mean that each copper segment can be extended to then support up to 255 node addresses (0 to 254) for the overall network. The actual protocols that run over this RS-485 physical layer are also very lean and efficient in data throughput. Profibus-DP is one example, but please note that Profibus does make a number of changes to the underlying RS-485 physical layer rules (capacitance and inductance limits, etc). Profibus-DP can run up to 12Mbps. Unfortunately, RS-485 is probably the single most misunderstood transmission technique due to a lack of understanding about bus termination requirements and correct screen connections.
Very good, RS 232, in most configurations, is point to point Where RS 422 is point to multi-point and RS 485 is multi point to multi-point. Where I once worked we made counter rotating, self healing, multi-master ring modems capable of translation from 485 to/from 232 to/from 422.
David Moran
This flexibility and ability to in effect cascade these different physical layers has also contributed to its longevity and success. RS-485 devices can also be used to replace failed stations in older RS-422 architectures with very little difficulty, although the reverse isn’t always possible. However, you can drop an RS-485 master into an existing RS-422 slave network with no problems.
Hi ! how can we use the RS-485 or RS-232 like does it have a relationship with the devices or cablee
nice video!. Thanks for teaching us all the time!
You're very welcome, Javier!
Special thanks real pars
You are very welcome, Rakib!
Nice and simple information
Happy to hear!
From baghdad ..thank you for this important information
It's our pleasure!
You made a Great job in this channel , thanks you to much
Glad you enjoy it!
Thanks for the stuff.
You are very welcome!
Good lesson and more helpful thanks
Happy learning!
Great video thanks
Thank you sir
Brief and useful information about RS-485. Thank you.
Great! You're very welcome.
Thank you for the easy to understand flow of this video. It really helped me understand the standard.
That is perfect Nick! Happy to hear that.
Thanks for your effort understanding
You're very welcome, Rahim!
the conculsion part of this video is really good!
Glad to hear that! Thank you
Thanks a lot.and more power.
Always welcome!
Brilliant video!
Thank you very much!
Nice tutorial regarding RS45 data cable in comparasion RS233
Thank you!
Thanks this time and every time.please keep doing the right things👍👍👍👍👍
You're more than welcome, Brahim! Glad to hear that you enjoy our video courses.
thank you so much!
You're welcome!
I like this easy explanation
Glad to hear that!
The 485 systems I work with can address 255 devices... 32 devices is the minimum unit load supported. 10Mbit is the fastest speed possible... you can't go as far in distance at that speed.
Right we do 99 just because we only have 2 addresses dial’s. Also 1000’ is about as long as we can go without a repeater. With networks way way over 4000’ total length.
You just explained in a high level. Can you put a video about RS485 with deeper electrical specs and communication data format
Thanks for your topic suggestion, I will happily pass it on to our course developers! Thanks again for sharing and happy learning.
Nice video thank you
You are very welcome!
thank you
Great video!
Thank you!
Great job ;)
Thank you!
Thank you
You're welcome!
My new residential heat pump uses rs 485 for thermostat and communication between the air handler and the compressor condenser. To bad Honeywell and others stick to the 5 wire c configuration…
Thnx so much sir for providing good knowledge. I request 🙏 sir please make video on advance mcc panel. Semocode working
Thanks for the topic suggestion, I will definitely go ahead and forward this to our creator team.
Happy learning!
Thanks!
You are welcome!
Plz, what's the benefits of RS485 for controlling a servo motor with arduino? ?
thanks
thank you really I like that. 👍🏻
I'm glad you like it!
Thanks
Thanks alot
You are very welcome, Sami!
yes its helpful
thanks
Great to hear that!
Just love it
Thanks a million #RealPars
You're very welcome!
Thank you so much
You are very welcome, Yusuf!
RealPars that was your pleasant.Good luck
Thak you from ...Iraq ...baghdad
You are welcome!
Thanks for this video.could you make a video for all type of protocol communication (Rs485,IEC,modubus)
Hey!
Thanks for your message and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Love it!
i guess Im randomly asking but does anyone know a trick to get back into an instagram account..?
I was stupid lost my account password. I love any help you can offer me.
@Kase Keaton instablaster =)
@Caiden Cristiano i really appreciate your reply. I got to the site on google and im waiting for the hacking stuff now.
Looks like it's gonna take a while so I will reply here later with my results.
@Caiden Cristiano it did the trick and I now got access to my account again. I'm so happy!
Thanks so much you saved my account !
@Kase Keaton Glad I could help xD
Can you give some more practical examples and working principle of the devices used here like HMI,VFD, etc
Hey!
Thanks for your comment and feedback! I will make sure to pass this on to our creator team.
Thanks for sharing!
Happy learning!
Very good
Thank you!
Great!
Great stuff!
Thanks for the extra lesson besides the every friday one on the library.
Now I understand a bit more the difference between RS-232 and RS-485 communications.
But then why are we still using it nowadays when we have Profinet (or Industrial Ethernet protocols)?
Hi Erick, thank you very much for the positive feedback.
Well, if you want to use a Profibus network in your project, you need to use RS-485 as a medium (cable) to transfer data. But for Profinet you'll make use of a CAT5, 6 etc cable.
So if you have a device that only supports Profibus, for example, you need to make use of an RS-485 cable.
Nice sharing
Thank you!
can you make a video explaining how to link the vfd with plc to control the speed of a 3 phase induction motor and how to program this process
Hi there, I will pass your request on to our creator team.
Nice and clear explanation 👌 I want to subscribe your channel
Happy to hear that! Thanks for sharing.
Thx lot
Great educational tutorial from RealPars, many thanks.
Glad it helped!
As always superb😇
Thank you!
Guys please provide basic programming of ac servo motor.
Regards
And thank you for this.
You're welcome! I will pass your request on to our creator team.
Thank you rp
You are welcome!
I did not know that the connector wasn't standardized, I thought that all DB9 serial connectors were wired the same. It turns out this is not the case, every device may be wired differently even if they have matching DB9 connectors.
Could You Please make video on XY MOD2 humidity & Temperature sensors and its connection with input modules and PLC.
Hey Dawood!
Thanks for your message and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Please explain about memory bits,Data blocks ,functional blocks,sfc in simatic manager...
Specify how to use them ?
Thank you
Hi there, I will pass your request on to our creator team.
Yes, I've been looking for the same thing.
Thanks
waiting for the PID course
👍🏼
YOU CAN VISIT MY CHANNEL FOR PID LECTURES.
So RS485 is a physical connection, and on top of it there is the protocol that makes the nodes communicate and control, like modbus, canbus, SCADA...is this correct?
Thanks.
Yes, RS485 is merely a physical (electrical) connection and as you mentioned, some defined protocols such as Modbus, Profibus and so on using it as one of their physical media to make their nodes communicate within the network. Thanks for your question.
Hi RealPars, thanks for such an informative video. I have a question though. You showed in the video that the PLC and VFD are connected via RS-485. But what about the input and output terminals? Are input and output (i/o modules) needed in this system for control? My understanding was that we use the i/o module of the PLC to connect the VFD or any other type of field sensors, but it looks they are not needed once we connect the VFD with PLC via RS-485. Can you please clarify between the difference or relationship between input/outputs and communication standard? How these two work together in a system? Thanks a lot.
There are several ways to connect a PLC to a VFD, and it depends pretty much on the model of VFD you are using. There are two main ways to connect to a VFD: hardwired and communication bus. With hardwired, there is an I/O board on the VFD that allows for wiring of PLC inputs and outputs to control and monitor the VFD. This would include analog signals (speed reference, actual speed, current draw, etc.) and digital signals (start, enable, alarms, etc.). For a communication bus (RS-485 based protocols like ProfibusDP, Industrial Ethernet, etc.) all signals are programmed and provided through a single communication cable.
Perfect
Thank you, Ahmed!
RS485 is defunct in many newer systems, Bacnet MS/TP or Bacnet over IP is the way to go now... We used RS485 for many years, I hardly see it anymore.
in china rs485 依然是低成本的主力军
@@newqf403 is it?
Thanks for your valuable information. can u please tell us about cable drawing?
Hey Hardeep!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
RealPars Greetings, speaking of drawings can you elaborate what program that is being utilized to generate these spectacular illustrations. Secondly, I’m late to the party but certainly enthralled that I’ve made it. Can you offer insight as well on courses for seeking certification, please or a POC (person of contact), much appreciated!
nice video
Thank you!
Please provide video on how profibus works?
Hi there, I will pass your request on to our creator team.
its a very good informative video. Just a little correction, when you say that an that an RS-485 network can only support 32
nodes. This is not true. Device manufacturers now sell 1/4 UL transceivers (DS1487) and even 1/8 UL parts (MAX1482).
Assuming each node presents 1/8 UL to the transmission line, an RS-485-compliant network may sport as many as 256 nodes (32 UL × 8 UL/node = 256 nodes).
Thank you, Mario! Much appreciated
really super
Thank you very much!
Can understand easily
That's great, Vishnu!
Thank you Realpars ,I have question Can i control VFD via RS-485 although the communication between the plc and hmi Via ETHERNET?
Yes, as long as the controller and the VFD have an R-485 communication option installed (interface cards). I designed a system not too long ago that had 5 different communication protocols (Ethernet, Profibus DP, Profibus PA, ASi, and IOLink) installed for communicating with different devices and components.
Hello!, do i have to put a resistance of RS485 half duplex at the end of the connection?
If the data rate is low or cables are short, termination may be unnecessary. As data rates and/or cable lengths increase, which is in most cases, termination becomes mandatory. Use of a 120-ohm resistor at each end of the segment will take care of communication signal issues due to impedance mismatches between devices. RS-485 is an electrical specification, and 2-wire protocols, like Profibus, which uses RS-485 as a communication medium, are half-duplex. In general, RS-485 installations will require terminating resistors. Full duplex RS-485 requires four wires, and is not very common in industrial control systems.
I'm creating industrial automation projects. Yes, my brand is not Siemens, but those interfaces are still widely used despite the opinion that they are obsolete. That is not true. RS-232 is used for PC program upload/download/online mode in my projects. RS-485 (together with Ethernet) is used as main interface between the devices. On the other hand equipment which supports EtherCAT, CANopen and other modern time interfaces is more expensive. In most cases fast interfaces are not needed, so RS-485 meets the requirements.
Thank you for your comments. RS-232 use is gradually fading, but it is still used in man applications, such as with programming terminals and analytical instrumentation (GC, HPLC, etc.). RS-485 (and its precursor, RS-422) are very heavily used as the physical layer for many digital protocols (such as Profibus) and interfaces. So yes, RS-485 meets the needs of many, if not most, interfaces between devices. Little by little, though, Industrial Ethernet protocols are being used for backbone networks due to its speed and ease of connection.