PLC vs SCADA vs DCS

is OPC UA the future of IIoT answering your questions question number three take zero all right so the last question on my answer for now is you want to read the question from the guy alright so the question was can you please come make a video that compares PLC versus SCADA versus DCS as how it pertains to OPC UA all right so in order to do that I gotta define these things all right so this is actually very simple so our PLC is our programmable logic controller out in the field the programmable logic controller has

IO inputs and outputs it's got a little processor running on it it's got some software running generally you can connect to it and you can write a control program that basically can read inputs and based on certain conditions make changes to outputs right that's your PLC the SCADA system supervisory control and data acquisition is a software layer that is designed to centrally control and acquire data from many plcs ok so I may have my SCADA system here my SCADA may talk to another PLC the big thing that SCADA does is it gives you control and

it gives you alarming that's really the big thing that skated us is it it tells us when we have a problem but it's central supervisory control and data acquisition is central dcs is very similar to SCADA but think of it as proprietary ok my SCADA system if I buy an off-the-shelf piece of SCADA software it generally doesn't care who the manufacturer of this Hardware in the field is ok it'll can talk to Allen-Bradley he can talk to Siemens it could talk to Emerson talk to anything right the SCADA software is generally open and it can

talk to anything ok a dcs system is generally in most cases it's processed specific and it's all of this stuff turnkey process specific so a dcs system dist a distributed control system has a SCADA component ok it has a SCADA component it has a PLC and oftentimes they call it a either a RIO and RTU or a PLC it has a hardware component okay out in the field most of the time that hardware in the field also talks to one another directly so I may have a RIO a remote i/o card that's at the beginning

of my process and one halfway through my process another one further up from my process there's some intelligence going on some i/o some intelligence going on on the edge and then I have a massive controller in a control room that's generally between the SCADA layer this is where the process control is taking place this is where the program is running and then my SCADA layer is really a node in the system okay so in distributed control systems I may buy a DCS from ABB so for example in the steel in the steel industry you use

distributed control in your rolling mill because the technology required the program required to run a rolling mill to turn a big billet into rebar is millions of lines of automation code so what happens is ABB writes the code one time you buy the distributed control system didn't they install all the i/o they install the process control center they installed the SCADA interface in the control room then they connect all that together and then they add in some custom stuff oh I might add in some additional i/o to turn-to-turn a water valve on here and there

and you can add in custom process control but with a distributed control system you almost always come with a prepackaged program in that DCS to run your process and then you kind of add on to it with PLC's and SCADA system think of them as blank slates right when I buy an allen bradley control logics it doesn't have a program on it I can take a program I've already written and put it on there or I can just write a new one from scratch which is the way it normally works a distributed control system can

complete completely blank but in this day and age normally it does not normally the DCS comes with the program to run your process already loaded on to it that and here's the reason you use a distributed control system is these almost always talk to one they're over a super high-speed field bus okay so generally these connections are not direct copper connections and they're not over Ethernet and they're not over fiber most of the time the SCADA control unit and all your remote IOs and your process controllers are connected over some type of field bus so

think of DC s as a turnkey solution that you can add on to to control your process and that turnkey solution includes the SCADA component but let's say I add a new process to my plant so I add in I install a new scale okay cuz I want to wait rail cars or something so I add a new PLC and I've got a rail car that I want away okay in this scale this Mettler Toledo scale comes up into that PLC most of the time you are not going to add the SCADA interface to the

DCs SCADA system why because it takes too long to do it right you can yeah and here's why because you know the companies that make DCs systems like ABB there are drivers that give us the ability to talk from our SCADA system through for example cap wear to their field bus system okay so the answer that's the difference the difference is is that think of SCADA in plc as the blank slate the open architecture and think of dcs as the turnkey solution but they if we were to Venn diagram their functionalities the two circles would

nearly stand right on top of one another a car would be a dcs they eat the electronic control model module the ECM module the flow control module the exhaust control module those are all distributed control systems for your car the unit itself whatever they call it you know like my Cadillac they call it something linked that is the dcs for my Cadillac right on Tesla Tesla is a to all Tesla vehicles are distributed control systems okay whereas the PLC is the actual brick it's the hardware and the SCADA system is the piece of software the

distributed control system is the completed solution automation kit would be more plc scada like you can kind of build your own correct that's exactly it yeah plc scada would be more like Lego or minecraft think of it as minecraft. PLC SCADA is like minecraft distributed control system is going to be like Mario level builder it comes prepackaged and ready to go but you can build your own levels if you want to yeah allen-bradley spam packs is another good in fact Alan Bradley's plant packs was a approach at answering DCs for for a labrat for rock

well anyway that was a really good question and thanks for watching