PLC for a beginner

[davesparks]

I’ve never used a PLC before but have found myself looking at a job which is going to put me onto that particular learning curve.
This is for lighting control, nothing to do with machinery or similar applications.
I’ve done a bit of research comparing features, price, availability, reviews etc and come to the conclusion that Siemens look like a pretty good bet. Does anyone here with experience in the field have advice? Are Siemens a popular unit or are they one to avoid?


I have looked at Siemens logo smart relays for other jobs and trialled them in demo software and found it to be pretty good but never actually got to using one.
I don’t think a smart relay will do this job as all the ones I’ve looked at don’t have enough I/O for what I need. At the moment I’m looking at 24 push button inputs and 48 outputs (based on the old, failing, system)

 

[Deleted member 26818]

Siemens and Trend seem to be most popular.

 

[LankyWill]

Allen Bradley are also popular but Siemens holds a large market within the UK and most people are trained with Siemens their support is also very good.

 

[davesparks]

Allen Bradley are also popular but Siemens holds a large market within the UK and most people are trained with Siemens their support is also very good.

It’s an Allen Bradley unit in the old system, with two old failed units sat in the bottom of the cabinet. The story is that the system has been trouble since it was installed and the old guy who knew how to fix it (from what I’ve seen this means he bodged and bypassed things until it worked) has now retired.
So the customer wants a whole new control system

 

[Bobster]

Right up my street. I'm not an electrician.

Siemens do a logo and Rockwell (Allen Bradley) have a micro 810.

Both are smart relays, they don't quite make it into the plc category. However they are cheap use the same basic functions and the software is free.

The software for PLCs is the biggest cost. For even basic stuff you're looking at 1k.

Schneider also do something similar.

All 3 are the same basic part with a different shell an badge. Different firmware.

Need any support just drop me a line, I can check part numbers, an if you end up struggling with code. I could write you it in 30min.

Just seen the amount of IO you need, look at a Siemens s7-1200. You should be able to get a starter kit for 500. You can't add many IO modules to those base models. However you could use some cheap et200 remote IO. Compact and have a small footprint. Are the digital outputs you need relay type or thyristor? As this will change the density you can get the modules in.

Also, for the cost of that many pushbuttons it would be more cost effective with a small 4inch touch screen. Save wiring and panel size. Plus you can change what you like on the fly.

 

[Deleted member 26818]

What about using LCMs?

 

[davesparks]

The software for PLCs is the biggest cost. For even basic stuff you're looking at 1k.

Need any support just drop me a line, I can check part numbers, an if you end up struggling with code. I could write you it in 30min.

Just seen the amount of IO you need, look at a Siemens s7-1200. You should be able to get a starter kit for 500. You can't add many IO modules to those base models. However you could use some cheap et200 remote IO. Compact and have a small footprint. Are the digital outputs you need relay type or thyristor? As this will change the density you can get the modules in.

Also, for the cost of that many pushbuttons it would be more cost effective with a small 4inch touch screen. Save wiring and panel size. Plus you can change what you like on the fly.

Cheers Rob

I’ve been looking at the S7-1200 starter kits, which if I’ve read it right include all necessary software along with a basic touchscreen for a sensible price as you say.

I’ve thought about the touchscreen option, but as an additional control station which they don’t currently have. At the moment the spec is to reuse the master panel and remote push button stations in each individual area.
Currently the system has all of the master station push buttons wired in parallel with the remote ones.

Some of the outputs will be switching contactors for the actual outgoing circuits and the rest operating LED status indicators on each remote station.

 

[rapparee]

The software is free for the plcs made by automation direct

AutomationDirect | The common sense way to buy industrial controls - https://www.automationdirect.com/adc/Home/Home

 

[gnuuser]

Ive used allen bradly most of the time but seimans equipment has a good track record.
with either plc whether you are using a contactor or directly wiring through a triac its always a good idea to place fuze's in the output circuits this can prevent damaging the plc.

 

[Bobster]

Cheers Rob

I’ve been looking at the S7-1200 starter kits, which if I’ve read it right include all necessary software along with a basic touchscreen for a sensible price as you say.

I’ve thought about the touchscreen option, but as an additional control station which they don’t currently have. At the moment the spec is to reuse the master panel and remote push button stations in each individual area.
Currently the system has all of the master station push buttons wired in parallel with the remote ones.

Some of the outputs will be switching contactors for the actual outgoing circuits and the rest operating LED status indicators on each remote station.

Yes the starter packages come with the basic TIA software you need for programming the PLC and HMI. You don't get all the functionality but you wont need it.

Something like this would be ideal:

6AV66517DA013AA4 / 6AV6651-7DA01-3AA4 - Siemens S7-1200 Starter Pack including CPU1212C ac/dc/relay, KTP700, s/w & doc - https://www.parmley-graham.co.uk/automation/siemens/plc-s/s7-1200/6av6651-7da01-3aa4

You will need an additional IO module or 2. It comes with a nice 7" touch screen and the software.

In my opinion, if you're using a lot of outputs just for LEDs, use the HMI to display this too. Saves wiring time, don't need as much IO and becomes more flexible. You can also add company logos and personalise it. In my opinion it looks far more professional. It's something really simple but for a client it looks impressive and they think they are getting more for their money.

You can have more than one HMI on the system. You can use them to display information about the system in the form of alarms. E.g a fuse has blown on xx circuit.

Like I said, if, whatever PLC route you choose you need a hand or something explaining let me know. It wont take me long to put together something for you to get you going or explain it.

 

[MFS Electrical]

Sorry for sounding like a dehngis but what exactly is a PLC?
I noticed Trend mentioned above I’ve done some work with their systems iq3 xcite and the 963 front end on BEMS is PLC just another term for that or am I barking up the wrong tree?

 

[Bobster]

Sorry for sounding like a dehngis but what exactly is a PLC?
I noticed Trend mentioned above I’ve done some work with their systems iq3 xcite and the 963 front end on BEMS is PLC just another term for that or am I barking up the wrong tree?

Yes, BMS systems use very basic PLCs. Usually with some form of telemetry unit so the system can be controlled locally.

A PLC (Programmable logic controller) is (simply put) a box, with inputs and outputs. The inputs go in, the logic insides then determines if an output turns on.

For instance if input 1 is on turn output 1 on.

 

[timbobelfast]

I’ve never used a PLC before but have found myself looking at a job which is going to put me onto that particular learning curve.
This is for lighting control, nothing to do with machinery or similar applications.
I’ve done a bit of research comparing features, price, availability, reviews etc and come to the conclusion that Siemens look like a pretty good bet. Does anyone here with experience in the field have advice? Are Siemens a popular unit or are they one to avoid?


I have looked at Siemens logo smart relays for other jobs and trialled them in demo software and found it to be pretty good but never actually got to using one.
I don’t think a smart relay will do this job as all the ones I’ve looked at don’t have enough I/O for what I need. At the moment I’m looking at 24 push button inputs and 48 outputs (based on the old, failing, system)

I have a stack of notes on PLC programming. Only ventured into the world of PLC last year. Took a Siemens course which was intense. Also use Mitsubishi FX and Q series. Prefer Mitsubishi to be honest! Software is expensive and Siemens is the more expensive of the two.

 

[Dave OCD]

I think in my case I'll continue to steer clear of this type of work.

 

[Kootni]

I have a stack of notes on PLC programming. Only ventured into the world of PLC last year. Took a Siemens course which was intense. Also use Mitsubishi FX and Q series. Prefer Mitsubishi to be honest! Software is expensive and Siemens is the more expensive of the two.

can you share the notes with us? email is: [email protected]; much appreciated.

 

[davesparks]

7 months on and the job is finally happening!

The first stage of the job has happened, the old control system is out and the new panel is in, I've got all the existing circuits working and returning next week to start the next stage of adding the new elements to the system.

I opted for the Siemens s7-1200 PLC and managed to get the hang of writing very basic ladder logic programs pretty quickly, or at least enough to get lights to come on when buttons are pressed.
And the bonus was that the program actually works!

I will update this thread as the job progresses and I'll try to get some pictures so you can all take the ----

 

[telectrix]

any useful info you can pass on regarding PLCs will be appreciated, digested then discarded. old dogs, new tricks etc. .

 

[timbobelfast]

Sounds promising, are you using TIA step 7 ?
What's the panel controlling?

 

[davesparks]

Sounds promising, are you using TIA step 7 ?
What's the panel controlling?

Yes, TIA portal step 7 which came bundled in the starter kit.

The panel is controlling lights. Specifically the backstage working lights in a theatre.

Control of these lights is via a master pushbutton station with some zones having their own local pushbutton stations. There is going to be a button at stage door to provide a last out / first in function. And also this system will incorporate 'grid beacons' which are flashing beacons to warn people of overhead work, this includes a sounder which will give a 3 second tone when the beacons are switched on and a different tone when they are switched off.

So it's very basic stuff as far as the PLC goes, but a good learning experience.

 

[gnuuser]

Sorry for sounding like a dehngis but what exactly is a PLC?
I noticed Trend mentioned above I’ve done some work with their systems iq3 xcite and the 963 front end on BEMS is PLC just another term for that or am I barking up the wrong tree?

a plc is a programmable logic controller ( as small real time automation control computer used in many pieces of industrial equipment such as conveyor systems, packaging equipment, or any process you want automated)
a plcc is a programmable logic controller computer! This is a dedicated computer permanently connected to a plc system to manage and program multiple networked plc, slc's and vfd controller banks found in motor control cabinets.

plc and slc systems use ladder logic programming and sometimes panel view for simple interface programming using block diagrams

 

[paul larratt]

Hi dave Eaton Easy plc are really easy to use and set up if you want to chat let me know
My field is automation on many types of systems and yours is anneasy one

 

[Blaspark]

It's cool that there's so many plc guys. Maybe someone could tell me what they think are the best systems with regard to diagnostics and preventing downtime and why?
I really only know about s7 controllers. I'd like to know how the s7 feature with respect to diagnostics and uptime compare to other brands/technologies.

 

[Blaspark]

It's cool that there's so many plc guys. Maybe someone could tell me what they think are the best systems with regard to diagnostics and preventing downtime and why?
I really only know about s7 controllers. I'd like to know how the s7 feature with respect to diagnostics and uptime compare to other brands/technologies.

And how close the languages are to the iec 61131-3 standard for the controllers we're discussing and maybe your preferred language to code in?

 

[timbobelfast]

Trained in Siemens TIA outside of work.

Use Mitsubishi in work with GX works 2.

Like ladder for troubleshooting and prefer to programme in FB. SFC is ok but prefer FB.

Have done some in ST but find it too nerdy for my liking. More like C language that software developers use.

 

[Blaspark]

Trained in Siemens TIA outside of work.

Use Mitsubishi in work with GX works 2.

Like ladder for troubleshooting and prefer to programme in FB. SFC is ok but prefer FB.

Have done some in ST but find it too nerdy for my liking. More like C language that software developers use.

And does diagnostics redundancy type features in the mitsubishi range? Are they there/good/easy to set up?

 

[timbobelfast]

We have a lot of HMIs around the site which aid troubleshooting without having to go into the programme sometimes if a skid is alarming as low pressure etc

The online diagnostics are also very good in GX works. There is a simulator to run programmes to debug offline if required.

 

[Blaspark]

We have a lot of HMIs around the site which aid troubleshooting without having to go into the programme sometimes if a skid is alarming as low pressure etc

The online diagnostics are also very good in GX works. There is a simulator to run programmes to debug offline if required.

What's the network/fieldbus?

 

[timbobelfast]

It's standard Ethernet on a dedicated process network. There are some CC link modules connected as well.

 

[Blaspark]

It's standard Ethernet on a dedicated process network. There are some CC link modules connected as well.

I'm not a fan tbh. I only really know profinet. The features seems exponentially better. Do you have redundancy features?

 

[timbobelfast]

No redundancy features such as slave CPUs etc. Reliability has not been an issue.
They are of course all on a UPS power supply system.

 

[Blaspark]

From what I see it just does redundancy with a loop. It's like profibus.
You have snmp though so not so bad

 

[Blaspark]

No redundancy features such as slave CPUs etc. Reliability has not been an issue.
They are of course all on a UPS power supply system.

You have redundancy available by creating a loop. Obviously I don't know how to set it up since I'm not familiar with you tech and it might only be available with certain hardware. It's available with cc link though

 

[gnuuser]

Im used to allen bradley but have studies siemans and profibus.
they all have decent features.
with slc racks we used in our machines if a cpu failed it was simple to plug a new one in and upload the program to get production going again.
most of the time troubleshooting was simple as you could see the processes on the ladder program, when a function in the machine was not happening, verifying it in the program allowed you to determine if it was in fact the program or the hardware in question.
knowing how the machinery is wired and what inputs and output numbers lead to the components allowed you to diagnose the machinery without . connecting the pc by observing the led's on the cards.
but thats not always the case with multiple machines depending on the training and whatever documentation is there or if it is missing.
its here (automation)where its important that proper training and documentation are stressed. downtime is costly but not as costly as improper safety.
as to writing the programs the absolute number one rule Make sure it is going to be safe to perform that function!

setting up redundant control systems however is a different animal
requiring master control cpus and redundant slaves this would be a complex situation to implement. (not to mention a very costly setup)
For most industrial situations there is rarely any need for a setup such as that (short of a nuclear reactor) and even so the inerrant weakness is one master control and one master output. these points are the weakest links

 

[Bobster]

You have redundancy available by creating a loop. Obviously I don't know how to set it up since I'm not familiar with you tech and it might only be available with certain hardware. It's available with cc link though

Only with S7-400 CPUs can you have redundancy with Siemens so far, they are still working on the S7-1500 to have that functionality.

You can have a profibus network wired in a ring with a suitable ring manager, but this is not the same as redundancy.

Redundant CPUs is not overly complicated to set up, but the cost is huge for the hardware. An then it is only the CPU that has redundancy. In my experience, as long as they are installed in a decent environment, these hardly ever fail. It's usually the IO.

 

[Bobster]

Just noticed a mistake in my post above, I should have said profinet, not profibus.

Profibus can be made into a ring topology, but needs a fiber optics with converters as a backbone, an to be quite honest I have never seen it done.

Profinet is Ethernet based, where as Profibus is a form of RS485 communication.

 

[gnuuser]

Only with S7-400 CPUs can you have redundancy with Siemens so far, they are still working on the S7-1500 to have that functionality.

You can have a profibus network wired in a ring with a suitable ring manager, but this is not the same as redundancy.

Redundant CPUs is not overly complicated to set up, but the cost is huge for the hardware. An then it is only the CPU that has redundancy. In my experience, as long as they are installed in a decent environment, these hardly ever fail. It's usually the IO.

I agree although triacs can handle the higher loads in some system its highly recommended to use fuses or overcurrent devices between the output and coil.
a fuse is very inexpensive insurance against burning out an output module.

 

[SheffSimon]

Just noticed a mistake in my post above, I should have said profinet, not profibus.

Profibus can be made into a ring topology, but needs a fiber optics with converters as a backbone, an to be quite honest I have never seen it done.

Profinet is Ethernet based, where as Profibus is a form of RS485 communication.

I have, in fact I was the one that did it, on a Siemens PCS 7 system. Redundant processors, redundant fibre ring, with redundant copper Profibus links from fibre converter to redundant remote IO processors. At a non-nuclear power station.

But you're right, it's usually the IO which fails.

 

[Automation ATO]

Have a try, you will know it

 

[Bobster]

Have a try, you will know it

After seeing several nonsense postings from yourself. I'm fairly certain this "user" is an AI bot.

 

[Automation ATO]

After seeing several nonsense postings from yourself. I'm fairly certain this "user" is an AI bot.

hello? I can't understand, who is a robot?

 

[koldwater]

Allen Bradley unit in the old system

The golden rule is to stick with the current brand of PLC used in industrial facilities. [Standardize] Plant maintenance (the true end-user) will already be familiar with it and may already have software for that brand, etc. Why? To reduce the customer's downtime, which usually costs the company way more than purchasing and installing a new brand of PLC.

But I always say, there are exceptions to every rule. Like in the example you gave, if it is not an industrial facility, like just lighting control. Another example exception, which you gave, they currently do not have anyone with experience, and there is a better brand for their application and location.

So, I agree with your thoughts, Dave. Siemens would be a better choice for this particular customer as it is the most supported in that country/region. During the equipment's lifecycle, there will be less downtime for your customer. Secondly, try to encourage the company to get some people trained on the new Siemens PLC.

Another golden rule is to do what is easiest and best for the customer, not for the programmer. Many automation control experts choose the PLC brand and programming language based on what the designer/programmer likes best and what is easiest/quickest for themselves. For example, Structured Text may be the preferred and easier PLC programming language for the programmer. Still, plant electricians may be more proficient in troubleshooting and modifying a PLC with Ladder Logic than a computer programming language like Structured Text. So, the true end-user, the maintenance staff, should always be at the top of everyone's mind.

That's my take Dave.