# How to start with PLC



## Electrical-EE (May 4, 2017)

Hy all & Thanks in advance. I am a newbie in the field of PLC, want to start with the basics of PLC hardware and programming. I have already started it from a book by Tony R. Kuphaldt and learning it. But I want some more pdf material to start with it. Please suggest a software (free version preferable) to start with programming and hardware. that is all about my question. Waiting for all positive talk and discussions

I already googled the pdf, but, Since I love Electrician talk due to its mature and helpful audience I thought to ask here.

Thanks again :thumbsup:


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## paulengr (Oct 8, 2017)

The newer PLCs from Automation Direct are Toyos and the software is free. They run $50-100 for the PLC itself. The software isn't Rockwell but pretty good. You can also get a free version of one of Allen Bradley's software systems that is somewhat limited but you can still use one if their lower end PLCs in the micro series. Contact Rockwell Automation if you don't know who your local distributor is. I find their PLCs are easier to use than the Toyo ones but that's partly out of experience. SoftPLC is another one. The software is developed by ex Allen Bradley programmers based on the PLC-5 platform but its entirely in software. You can put the PLC on your own Linux hardware or buy theirs. Codesys is a popular European name that you wouldn't immediately recognize. They developed a fully IEC compliant PLC and software and license both to just about anyone so a lot of European PLCs are actually Codesys loaded onto industrial PC hardware. Togo by the way is similar...the current generation may not be but the last generation of GE branded PLCs were actually Toyos.

At one time PLC hardware consisted of a set of very custom ASICs and some fairly simple CPUs (if it truly had one) running some kind of interpreter. The software side was a graphical (hopefully) system to create tokens (numerical numbers so for instance an open "contact" might be instruction opcode 1, closed might be opcode 2, etc). Somewhere in the 1990s this evolved into general purpose CPUs and today's code is actually compiled and the interpreters are gone. The hardware is just an industrial embedded controller (special purpose PC). So today's PLC is not that different from say an Android phone where Android runs on top of a stripped down operating system, almost always SELinux, on custom hardware. If we substitute "PLC" for Android we get the same thing.

On the programming side there is an IEC standard. The basic structure and some functions in the PLC software are slowly becoming nearly identical from vendor to vendor but for instance Siemens S7 online mode is a real bear to work with and there is still a lot of differences between PLCs in terms of advanced instructions, copy/paste, subroutines or some kind of code reuse system, and other helpful tools that improve code accuracy and efficiency.

Hands down though you can find better but nobody is as over the top crazy overpriced as Allen Bradley. Their newest PLCs can easily top $10_000 or more just for the PLC itself and their software can run over $6,000 for a single license! Compare that to where I started with PLCs that are under $100 with free software. And that's nothing compared to the insane my overpriced stuff you get into with DCS systems. The minimum price for a "basic" system with those runs around $1 MM without I/O and has roughly the power of just one AB PLC. But wait...they also charge annual license fees per I/O "point" for DCS systems and will take down your whole plant if you don't pay up. Microsoft would kill to be able to sell ransomware like that.

Granted Allen Bradley has reduced system integrator pricing but it comes at a price. They are very heavy handed and try to do everything they can to make you buy every component from them even though they are usually overpriced by about 300% across the board. And then the fun part...unlike every other manufacturer they hold the end users hostage dealing with only one specific distributor. That's OK if you have a good Allen Bradley distributor. But some of them are truly awful.

There is just one caveat to this. About 85% of U.S. PLC installed base are Allen Bradley. So if you are in the U.S., you need to be familiar with Allen Bradley at some point. If your local area has a horrible distributor such as in Raleigh or Omaha then this is going to be a bad experience. Get used to Radwell....buying AB with about a 65% markdown and a decent supplier which makes it tolerable. I've been blessed and burned on eBay too too many times to consider it a reliable source.

So...keep in mind that the PLC world can quickly bankrupt you if you let it.


Sent from my Galaxy Tab 2 using Tapatalk


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## triden (Jun 13, 2012)

paulengr said:


> The basic structure and some functions in the PLC software are slowly becoming nearly identical from vendor to vendor but *for instance Siemens S7 online mode is a real bear to work with* and there is still a lot of differences between PLCs in terms of advanced instructions, copy/paste, subroutines or some kind of code reuse system, and other helpful tools that improve code accuracy and efficiency.


Just curious, can you elaborate on the bolded? I'm a Modicon guy, but have been using S7-1200's with TIA V14 at a plant making some changes. I'd like to know what you think of the S7 architecture as Siemens is really pushing us to start using it.


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## paulengr (Oct 8, 2017)

triden said:


> Just curious, can you elaborate on the bolded? I'm a Modicon guy, but have been using S7-1200's with TIA V14 at a plant making some changes. I'd like to know what you think of the S7 architecture as Siemens is really pushing us to start using it.




Three issues with S7. The first is that when you are in online mode, only one or two active lines are in online mode. The rest of the screen looks like online but it's static. This is very confusing even if you know what it is and have experience. S7s are not really intended to do online troubleshooting.

Second is their Ethernet I/O at least with their starters is very unstable and erratic. Can't figure out why. Been fighting this for a long time and Siemens is stumped. If you use standard I/O it seems to be fine just not their "smart" starters which randomly start, stop, or stop changing states with no errors. My overall impression of Profinet is that they didn't understand Ethernet so they bastardized it with something that kind of sort of works on the same cabling but don't look any deeper. They basically tried to turn Ethernet into token ring Arcnet and ended up with something that takes the worst features of both. Again...difficult at best to troubleshoot.

Finally Siemens programming style is to develop your own libraries of functions everywhere. But there aren't standard libraries and for instance where in RS-Logix you can view the code in the user defined function with variable substitutions so that you can basically "flatten" the code for troubleshooting, this is difficult to impossible in S7. The underlying instruction set is so weak that avoiding user defined functions is simply not practical.

The library thing is that essentially you program an S7 the same way you do in PC programming. A program consists of dozens to hundreds of modules built up in layers. The problem is that it makes it extremely difficult to do any kind of troubleshooting with the PLC. It is inherently difficult to trace code so maintenance will struggle every time a machine breaks down.

The I/O is tiny...need #16-18 wire and a good magnifying glass and lighting. And it's not very reliable.

Then there's support. I know one Siemens system integrator in the Carolinas...one. But dozens for most other brands. Don't expect stellar Siemens support either. Most of the time the vendor can't help you even if they are close by.



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## oliquir (Jan 13, 2011)

id say start with programmable relays, then go into small plc and go bigger when ready


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## Rora (Jan 31, 2017)

Factory IO... /thread.

It's a sandbox-style PLC simulator where you can create virtual automated environments. It's 100% realistic, in fact the virtual equipment can be run off of an actual PLC if you don't want to use the PLC emulator in the software.

I believe it also has pre-made troubleshooting exercises.

https://factoryio.com/

Just playing around with a PLC without seeing how it interacts with "real" equipment is like trying to learn programming by typing out syntax without compiling/running.


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## Electrical-EE (May 4, 2017)

*I will check it.*



Rora said:


> Factory IO... /thread.
> 
> It's a sandbox-style PLC simulator where you can create virtual automated environments. It's 100% realistic, in fact the virtual equipment can be run off of an actual PLC if you don't want to use the PLC emulator in the software.
> 
> ...


Thanks for the link I will check it as well.


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## Jacobsunil (Oct 25, 2017)

I am looking forward for a real hands on practical work training with PLC programming and installation works . 

Please let me know if anybody in PLC programming trouble shooting business need support . I am ready to work in assisting main programmers or installers of PLC systems.


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## sparkiez (Aug 1, 2015)

Jacobsunil said:


> I am looking forward for a real hands on practical work training with PLC programming and installation works .
> 
> Please let me know if anybody in PLC programming trouble shooting business need support . I am ready to work in assisting main programmers or installers of PLC systems.


There are job sections on these sites. It is considered rude to hi-jack someone else's thread like this. :no:

Here is the link to the job classified section of this site:
http://www.electriciantalk.com/f65/


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## Jacobsunil (Oct 25, 2017)

Thanks @sparkiez for showing the way ;-)


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## John Valdes (May 17, 2007)

What seemed to help me the most was installing PLC's and the wiring on machines.
Back then I did the pipe work, pulled the wires, marked the wires and terminated them to the PLC. I did this from drawings. Very very easy.

Then when I started to learn how to program them, it was easy as well. But I already had control experience. So that also played a big role.
As you can see OP I was able to get the experience on the job and becoming a pest to the PLC manufacturer.


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