why industry use PLC?

Thread Starter

liamneeson248

Joined Jan 11, 2016
36
I know about this amazing arduino microcontroller which i use to control things in my house and other automations and i also happens to know about PLC my question is why people aren't using Arduino in industry as they are using PLC to perform industrial works ?
i know PLC is solid and it can survive Temperature and all and what if we can put arduino in some hard good case then can we use it in industry ?
Yes arduino works on 5v but if can use normal 5v arduino relays to power other power relays and that can work fine in industry
 

Picbuster

Joined Dec 2, 2013
1,020
PLC do, as you know, have a hardware save state this to avoid a problem controlling a chemical process.
Next to above the insurance companies will only accept well proven concepts.
Nothing wrong with MPU systems but the rules above do block many (small) companies building controllers.
And a PLC is driven by ....yes.... a MPU so...... it's emotion, law and the insurance branch dictating goods to be used.
 

KJ6EAD

Joined Apr 30, 2011
1,569
Plus you can buy dozens maybe hundreds of PLCs for the price of one arduino.
:confused: PLC (Programmable Logic Controller), not PIC. PLCs cost hundreds to thousands of dollars depending on brand and configuration. They have some advantage in the area of EMI/RFI resistance for industrial use but there's no inherent reason why an inexpensive hobby microcontroller couldn't have the same toughness added in the form of TVS, MOV, GDT, optocoupler, common mode choke, shielding, etc.
 

strantor

Joined Oct 3, 2010
5,322
I know about this amazing arduino microcontroller which i use to control things in my house and other automations and i also happens to know about PLC my question is why people aren't using Arduino in industry as they are using PLC to perform industrial works ?
i know PLC is solid and it can survive Temperature and all and what if we can put arduino in some hard good case then can we use it in industry ?
Yes arduino works on 5v but if can use normal 5v arduino relays to power other power relays and that can work fine in industry
There are a few good reasons :

There is no way to view/modify the code of an arduino. Only the original programmer or someone who has obtained the original program can modify it. Most people (myself included ) would never buy a machine costing thousands (or millions ) of dollars that is controlled by a black box that maybe only one man on earth knows how it works. What if that guy quits, dies, gets fired, loses the files, or the company goes under? Regular crew maintenance guys need to be able to view the programming online in real time, and understand how it works, to be able to troubleshoot effectively.

...which also means it need to be stupid simple programming that even a hammer fisted wrench monkey can pick up with minimal anguish. Most people look at text code and their brains default to the OFF position.

PLCs support all the common comms protocols, voltage levels, analog I/O, and are scalable . Arduino can't make those claims.

PLCS are exhaustively tested and certified for safety and other factors.

Plc manufacturers typically offer 24/7/365 tech support. When a machine goes down and it's costing you $10k/hr, you damn well better be able to call someone who knows WTF they're talking about, immediately. I'm not aware of ANY official tech support for arduino.


I have seen arduino used in small production machines and I think that's about as far as it's suitable, if even that. If the machine costs more than a couple thousand dollars, or generates more than a couple thousand dollars/yr, I think it has graduated out of the realm of arduino.
 

MaxHeadRoom

Joined Jul 18, 2013
21,204
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nsaspook

Joined Aug 27, 2009
7,470
Writing micro-controller computer code for an industrial application that might involve a large product or human risk is not trivial even for something simple. Try upgrading a simple 20 year old RPM sensor in a system that used variable reluctance sensors to a custom in-house controller that uses modern Hall sensors to detect the much slower RPM in the new design while emulating the original output signal. 20% of the hardware and programming task is reading the input signals and outputting the correct signals in a high electrical noise industrial environment. 80% of the task is making 100% sure that output signals only happens when they should, designing hopefully as fail-safe code as possible for when an error does happen, displaying those errors in some machine or human readable form and creating the build/coding/troubleshoot documentation so some person other than me could make/fix the next one. I would have used a PLC type system in an instant if I could.
 
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GetDeviceInfo

Joined Jun 7, 2009
1,732
You'll discover that tons of industrial equipment does in fact employ micro controllers. The 8051 core is likely one of the most popular devices in interfacing. Arm cores are pretty much everywhere. Functionality determines the core that is applicable. Simple displays, input devices, and devices wth limited intelligence could easily be driven with AVRs and lighter ARM cores. Make no mistake in the sophistication of modern PLCs. High performance RTOS providing broad functionality. Not to mention industry standardization, regulatory compliance, performance guarantees, etc. No doubt, the cost and somewhat consistent IDE will see the Arduino increase in R&D, and many of those cores will make it into commercial applications, but 'PLCs' are typically far above the 'hobbists' Arduinos performance.
 

NorthGuy

Joined Jun 28, 2014
611
PLCs are bad no matter how you slice it - big, slow, inefficient, hard to work with and incredibly expensive. But the people who sell them are good marketers and lobbyists, so they screwed the public opinion towards the idea that PLCs are proven, safe, industrial etc. These people work so well that if you ask any (well, almost any) engineer, he'll tell you that that is all true, but he won't be able to tell you the reason except - proven, widely accepted, trusted, approved and similar gibberish.
 

MaxHeadRoom

Joined Jul 18, 2013
21,204
Then it is odd that the vast majority of world wide CNC machines also use include a PLC for the machine I/O control side of things!:rolleyes:
Which incidentally must number in the many millions by now.
Max.
 

GetDeviceInfo

Joined Jun 7, 2009
1,732
PLCs are bad no matter how you slice it - big, slow, inefficient, hard to work with and incredibly expensive. But the people who sell them are good marketers and lobbyists, so they screwed the public opinion towards the idea that PLCs are proven, safe, industrial etc. These people work so well that if you ask any (well, almost any) engineer, he'll tell you that that is all true, but he won't be able to tell you the reason except - proven, widely accepted, trusted, approved and similar gibberish.
Whoa, I think your charging down a different path. PLCs are no different than any other 'system'. They have been proven for applications that warant them. Engineers who make poor choices don't reflect on the validity of the PLC. My work is typically industrial installations, commissioning, and production tuning. My hobbies are typically embedded anything. Grouping IO as opposed to dispersing it has it's pros and cons, as does running localized over centralized software. Cost is a major contributor as are the operational objectives.
In the last 4 years I've installed two manufacturing plants with a broad range of equipment. IO was spec'd, PLCS /HMIs purchased, installed, wiring pulled and terminated, software roughed in, tuned on commission, dynamic tuning, done. Try that with an Arduino.
 

strantor

Joined Oct 3, 2010
5,322
PLCs are bad no matter how you slice it - big, slow, inefficient, hard to work with and incredibly expensive. But the people who sell them are good marketers and lobbyists, so they screwed the public opinion towards the idea that PLCs are proven, safe, industrial etc. These people work so well that if you ask any (well, almost any) engineer, he'll tell you that that is all true, but he won't be able to tell you the reason except - proven, widely accepted, trusted, approved and similar gibberish.
The idea that PLCs are proven, safe, industrial, etc. was around for a long time before Arduino came along. So what were these supposed marketers and lobbyists fighting against all that time? Maybe that notion has existed for the past 2 decades because it's true? If you rewind back to post #7 you'll find an engineer who just listed off several reasons, most of which not regurgitated from a propaganda pamphlet.
 

NorthGuy

Joined Jun 28, 2014
611
IO was spec'd, PLCS /HMIs purchased, installed, wiring pulled and terminated, software roughed in, tuned on commission, dynamic tuning, done. Try that with an Arduino.
PLC is just a box with an MCU inside. The MCU is oversized for the task to support rather clumsy PLC software. They're overpriced - the manufacturer gets very good margin. Imagine, instead of PLCs you were given a bunch of boxes with microcontrollers inside, which, unlike PLCs, would be created for the specific task, the software would automatically tune-up and configure itself. Everything would cost much less, and you would have less work commissioning it. It is possible (technically and economically).
 

strantor

Joined Oct 3, 2010
5,322
Are you sure about that?
Have you ever play with arduino?
Yes, i have. I love my arduinos, for my hobbyist endeavors. If you could teach me how to suck the programming out of an arduino that someone else programmed, add a simple instruction linked to a new digital input, and then monitor the status of I/O in real time to verify the new sensor is doing its job, that would be awesome.
 

strantor

Joined Oct 3, 2010
5,322
Oh @NorthGuy i remember you. I remember having this idiotic discussion with you already in the past. I think it was your own thread, and you were asking why anyone would use a PLC instead of a microcontroller. You kept banking on the fact that PLCs had microcontrollers inside, which i turned around on you to reveal the stupidity of your argument. I believe i said something like "why would anybody use a truck, when they could use an engine for the same purpose? Because they would have to build a truck around the engine, at which point it would have made more sense to just buy a truck."

I see now that none of that sank in. Oh well.
 
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