Industrial Control
Erik Friesen
Posts: 1,071
Timothy said...
Erik - what do you mean by compatible? I think of the PLC or the Prop Controller as different tools to be applied. In general, designing control system is a method or process, and the tools used to get the job done depend on experience, system requirements and personal preferences. Using a PLC vs a Prop controller may require some different implementation process, each with advantages and disadvantages. For safety systems, there is no way I would use a Prop - at least not without lots of time and money in design and analysis. I would rather implement a safety PLC properly because those answer a host of issues I can't begin to tackle with a custom Prop design.
I worked for a client that built automated or semi-automated brazing machines. They used Allen Bradley hardware mostly, but those machines were simple. That was a couple years ago and our company has done work for them off and on. If I had an opportunity now, I would propose a Prop Based system because it would really reduce the cost of the controls since the machine was simple, it really didn't need a SLC505 PLC. Of course, their clients wanted easily serviced/replaced equipment, so they may have to coach their customers into using the custom controls. The system I envision looks like many of the pictures that John has posted.
I mean electrically compatible. It seems a little easier to use off the shelf exterior controls to control high voltage applications, for example.
Can you elaborate just a little on the advantages and disadvantages of a PLC vs Prop?
What are a few of the safety issues that a PLC addresses? ( I assume you mean personal safety)
Realistically, do you think someone with a little programming experience would have much more trouble learning to modify an existing spin program(with a little coaching) versus ladder logic or other PLC language?
Comments
This looks like it should have been a reply to an existing thread, but it is a new thread. Was this intentional?
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Chris Savage
Parallax Engineering
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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
I apologize for a slow replay. First, I appreciate starting another thread as I too didn't want to hijack the other thread where I brought these topics up.
Making a industrial controller with the Propeller at the heart of it is an interesting idea, one that I like to think about. There are advantages and disadvantages in both ways. Of course, the controller can be made to provide the electrical interfaces required for industrial settings. Providing those interfaces is only a matter of specifying them, designing them and testing them. I prefer 24V DC input/outputs, but other system might be 12V DC or 120/220V AC or Relays or opto isolated or sinking or sourcing or or or etc. There have been a couple other threads of how people have integrated the Propeller into industrial systems, so we can learn from their experiences too. For a basic controller I would think of x number of 24V DC inputs and y number of 24V DC outputs.
Buying a known PLC brand is much different than buying a Propeller controller that I cook up or someone else cooks up. First there is the long term support issue - what if I decide to not make the controller any more? Next is the user base and install base - some PLC have been around F-O-R-E-V-E-R. That means that maintenance teams, customers and repair teams are familiar and comfortable to a specific product. They have inventory of spares. They know how to fix a system if a problem comes up. Their teams have confidence when they see the PLC brand (or they hate it - depending on the brand). This can make it difficult to sell a client on new technology or brand, no matter how great it looks/feels/acts/performs. This is common dilemma in any selling.
A disadvantage of a PLC system is that they can be costly and general purpose enough that they are designed to meet all your needs - and then some. Some designs requiring a PLC are very specific, rarely change or have cost or space constraints. These types of system require perhaps more of a embedded solution - thus the Prop Controller would be a great idea to reduce cost or space usage or to make a controller very specific to the application. In addition, there are various tools that are required in order to use a PLC such as the programming software or network viewer. In many cases those tools also cost. With the Prop Controller you could use the Propeller Tool or ICC or etc that are free or not so much money.
Safety is very important in system that are designed and sold and used in commercial or industrial applications. I don't just mean personal safety, I mean protecting from any dangerous system design that could harm person or property. Protecting from damage property is important. Safety and having something be safe isn't about what PLC is used, or what photoeyes is used or what contactors are used - safety comes from an overall system design. Now, there are products that are "safety" products and with their proper implementation make a system safer or safer system is easier to design. The key is properly applying those products. With a Propeller controller a system can be designed to be safe. In Europe that are standards for Safety Integrity Levels (SIL) - there are different levels with varying requirements for what is safe and what isn't. The Prop Controller won't get you to certain levels - not without a lot of engineering and design and certification and proving of the device. But again, certain systems don't need SIL levels - they need a general purpose controller to do XYZ.
I hope my ramblings are helping you to see some advantages to PLC vs. Prop controller. It depends on the system requirements, customers and you as the designer.
It is hard to compare if some person can easily go from SPIN to ladder logic or vice-versa. It depends on the student and the teacher - as well as how well the code in either system is designed. The system that I have been a part of recently had only some ladder logic, we have actually been using structured text and flow chart diagrams and other elements to do the programming. Some of our customers think it is great that we can effeciently make a system and present it and get it running using the best tools. Other customers hate that the system is not completely in ladder logic because they "don't understand stuctured text or flow charts". Aye aye aye!
Programming a system in ladder logic or in SPIN is going to have slightly different approaches, especially with multiple COGs. Again, care must be taken in the system design to ensure it fails properly, action occur when expected, etc.
Again - rambling here. Is this helping?
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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com
In the area of PID, is ladder logic still used?(for plc) Or would that be a subsystem?
Again, thank you for you replies. One thing I appreciate about this forum is that dumb sounding questions get answered. There are numerous ways to learn new things, and asking questions is one of them. I have seen similar questions asked in other forums where the forum members went off into a degrading rant about the dumb question, and never even attempted to answer the original question.
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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
ie. step forward 30 times grab block step back 6 ...
can be done in ladder logic but c would be easier.
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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
For PIDs, it depends on the applications and equipment. Some controllers have built in PID functions, some system use an external PID device and yet others may be a combination.
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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com
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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com
The direclogic software is around $400.
The Cmore software is around $125. It seems extremely basic in some respects.
I just have a sneaking suspicion that the cheaper plc brains and software will choke at the pid loop that will control the misc air and feed controls for the gasifier.
They want graphics sort of like this www.youtube.com/watch?v=l8BUIOmMHe4 (scroll ahead to 8:50 - 10:10) and I am just not sure that there is sufficient memory in the prop chip + vga + ethernet to do this sort of thing.
Are there some brands that you would avoid?
Post Edited (Erik Friesen) : 3/17/2009 12:45:14 AM GMT
The Operator Panel in the video 08:50 is (I think) a Siemens Simatic OP37. They cost many thousands of dollars. Its used for changing setpoints and starting and stopping processes in the PLC. It doesn't do 'processing' but writes to / reads from the PLC memory. It also applies limits and password security to prevent unauthorised use. It would usually connect to the PLC using ProfiBus which is a Siemens network protocol (RS485 based I believe).
Such an OP really isn't doing much that the Prop couldn't do, except for the Profibus connectivity. However the proprietary connectivity and 'industry standard' tools (& know how) are big barriers to entry for things like the Prop. Also while the hardware is expensive by Micro standards the engineering time often betters it.
Later in the video there is a SCADA system with 'mimics' (graphic representations of the plant). Again the SCADA system just interacts with the PLC's memory, but presents information graphically. The Prop isn't really capable of replacing SCADA systems except for basic, simplified graphics (or line graphics from the character set).
If you're just starting in IA: Because the PLC/SCADA gear is expensive and micros so cheap, there are all sorts of products in between. Steer clear of the clone/cheap brands at least initially. Start with a low-end-but-feature-packed name brand PLC (including PID control). They are a few hundred dollars. Many of the best SCADA packages have a trial mode. You can run free for one hour, then you have to close and restart the program.
Tuning PID control loop parameters is tricky. Hence the 'autotune' feature often present.
tubular
I just have a sneaking suspicion that the cheaper plc brains and software will choke at the pid loop that will control the misc air and feed controls for the gasifier."
While its true you do need a PID 'block' in your PLC, for slow moving stuff (valves, VSDs etc), even the cheap ones will work as well as the expensive ones. The trick is to get the gain term / time constants right to get the process to run well. Often you don't need much 'D' and a PI controller will generally work pretty well.
Also being able to chart/graph stuff (a common SCADA feature) is invaluable during commissioning, especially where PID loops are also involved.
any other questions just ask.
tubular
Beside Profibus many other protocols are supported by those OP As a experienced programmer/developer on PLC (Siemens S7/S5 guru; good SchneiderElectric(Telemecanique); discrete AB, GE Fanuc and Omron) I can say that many PLC has many choices of programming languages (one of them for sure ladder). I agree with both Mctrivia and Tim. It happens often times to me that the customer request ladder logic for I/O handling·(eg overload protection that stops the motor), because of his unskilled maintenance personnel, while the process management, due to complexity, is written in higher level language
BTW: I have never found a integrated PID that was good enough to be more than·generic use (good for some basic water level control or simple temp control) and I am not referring to predictive(?foretelling) and auto-self-tuneable/learning multidimensional fuzzy neural networks
Is this all on the same plc brain and with the same programming software?
Do you know where siemens products can be bought?
I built myself a car cruise once, and found out about the difficulties with pid.
I just have a feeling that with the multiple inputs and outputs involved that writing my own code in c (for the PID) or the like would be preferable. Any recomendations on a series that can allow this?
Thanks again for this treasure trove of info.
PostEdit: Total 6 files, the last in next post (below)
Post Edited (dMajo) : 3/18/2009 1:34:04 AM GMT
I think that a S7-300 series will be OK (you need to look at Siemens site because there is many variants).
- Standard - only cpu you need additional modules
- The compact units have integrated counters, AIO and DIO. (you save money on IO expansion cards)
- The F category is fail-safe: emergency goes on the bus, no need for additional wires and safety modules, certified.
- Other have Technological functions: multi-axis up to 32.
For sure you will not need S7-400 series (part of my daily developing job is based on them). This units are used- where there is a need for many IO with high process power (eg paper industry/iron industry: synchronised high speed multi-axis with torque control; iron industry or (
- H category fault-tolerance systems double cpu, double io card: if one get damaged the sleeping brother instantly wakeup and take control (used where a damage could lead to big system/personnel injury/dead (eg. turbo-gas electric centrals, explosive gas compressors, petrol-chemical refinery)
- multi-processor "multicomputing" systems
Take a look also on Siemens C7 units: PLC with IO combined with OP in one unit. For higher demands·have a look at MP·(can act also as plc-cpu)Siemens is not so cheap but one nice thing is that in the most damned place to the world you just cross the street and you have a Siemens shop
Languages:
Development system: quiet expensive but you have also ligh versions. One suggestion: the Premium studio is a collection (multi-DVD) of everything which will really semplify the software setup (can take two days to install everything with separated CD/DVD answering to setup questions - required 16GB on hdd), you have to purchase separalety the license for each product you need (on public forum I prefer not teach you how you can get them free) cc
Attached you will find some help files (taken from installation folder)
Post Edited (dMajo) : 3/17/2009 8:48:16 PM GMT
Normally this is done in the same (modular) development environment. It depends, sometimes each module has its own license and/or you have to buy it separately.
When I buy parts for work at the whole salers they don't even have a price listed. they just send a bill monthly to my employer. some time people ask how much something costs and usually I have to say "Don't know."
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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
This thread has been highly interesting and fun to write/read. dMajo has lots of great advice and experience it looks like. My experience is mostly with Allen Bradley PLCs though soon I may have to learn some Siemens technology as we have been getting more requests for it.
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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com
It seems overkill to use a $1500-$3000 hmi just to get a semi-smart 15" monitor with ethernet.
I wonder whose I/O quattro is using?
What kind of graphics capabilities could a person implement using two props, one to take care of the graphics? (VGA)
dMajo - thanks for the info so far. I am still mentally digesting this info.
They miss a Parallax style forum: answer is not so quick.·They have excellent phone support: when you are in troubles you place a call, they register you and in few hours an engineer will call you back.
To view the files winzip is enough: I posted them in two post because of the 5 attachments limit (total 6 files: download all them in the same folder and double-click the one with zip extension).
It is not problem at You have files on 2 posts but "z01" have bad extention.
For al that wil open files.
Download xxxxx.z01 file ... It have ".zip extention"
Rename to xxxxx.z01 and download al other files and unzip
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
Thinking it about it some more, my recommended starting point would be the Zelio Relay from Schneider Telemechanique. Here's why:
* It has a 4 line lcd display, you can program / modify setpoints via the display
* Alternatively program it using PC software
* You can program it in Ladder (sparkys native tongue) or Function Block Diagram (FBD) using the PC software
* The serial port on it uses Modbus which is a simple RS232/RS485 standard and would be easy to interface to the Prop or PC
* Its from a major brand and good quality.
* They have starter kits which are a few hundred dollars including the relay/PLC, programming cable, and software
* List price on the starter kits is around US$370 but you can probably get a good discount off that.
* You can download the software for free and have a play (on that site)
They have a good, contained (compared with Siemens A&D mall) web page here
http://www.download.schneider-electric.com/WEBKITS/Automation/ZELIOLOG/en//index.htm
including applications information and examples etc
I will check for you whether it supports PID. They do have an analog expansion module which has 2 analog inputs and 2 analog outputs for US$180 list.
By the way IEC1131 is the standard for programming PLCs. It defines 3 languages, Ladder, Statement list and FBD. They are interchangeable and many programming environments let you convert you code from one to another and back again. At least in theory (sometimes things get lost in the translation!)
I believe you are in the US? Another US product which I used and was nicely contained, cost effective and user friendly was the Horner OCS http://www.hornerocs.com/
I realise these options are a step back from what I previously suggested, but they are a cost effective starting point. There's a steep learning curve with something like Siemens Step7, you need someone to guide you through it, or you will lose much hair
tubular
I was not aware of it. The name showed on the web page is correct (.z01). I tried to download it and on the save dialog box the name is wrong (.zip) but I don't know how is happened.
From your post I assume that, once downloaded and fixed, you was able to unzip.
I am going to be away from my computer so I won't be able to do much research today.
- Anybus CompactCon - Technical Overview
- Anybus-IC - Technical Overview
beside the above there is also this products (I haven't used them but I heard many compliments on)
- profichip ASICs
- STEP®7 PLC processor
@Eric,
BTW:·VIPA plc is build on the above processor. I forgot to mention it on previous post. The Vipa product now is mature enough and I can recommend it to you. You can mix Siemens and Vipa without any problem (expansion cards mounted on left side of the cpu - serial bus) and you save on money. The fast expansion modules (mounted on the right side of the cpu unit - Speed7 parallel bus) require a Vipa cpu. I have worked with them, without any trouble, using the Siemens development system. Vipa have its own developing platform that supports also Siemens line of products, but I have never used it (probably is cheaper). I doubt it works on S7-400 because Vipa haven't a corresponding platform in their products list.
Take a look also on PI site. They have S5/S7 IDE (running also on "palm organizers - I haven't tested").Here you need to download the documentation because the site have a very bad and/or missing english translation. I have around the world more than 200 systems based on Siemens/S5·running with their Teleservice product (version 1). In the pre-internet era ('90) I tested several competitor products and I found this wonderful: it worked at the language layer. Eg: when transferring through serial/modem, if you have two bits wrong in a byte, you can have still the parity check OK (the same can happen with CRC and other error correction methods): this product inspected the program you was uploading (in real-time) looking, if·can recognize the instructions and if they have sense (eg. you can not write to eprom/rom), prior to crash your remote plc. All this happened without any setup, transparently to you: 2 units were needed one on each side.
Today best solution (in my opinion) is to have a PC (on customer site) with raid storage, (two) network card(s) (if you/customer want/need IT-Ethernet separated from the industrial one)·and/or a Siemens CP5613A2 profibus card, all·running on XPpro/2003Server with all the Siemens development environment and plc sources installed on it. You simply connect through VPN and work on this PC by a remote terminal session. The IDE can be at zero-cost for the customer/supplier because the new Siemens licensing system is based on floating licenses (you even not need to transfer the license because the remote IDE autenticate on your pc/laptop license-server service, of course your local IDE should not run otherwise you'll need multiple licenses on it). It happen several times to me, to connect remotely on plc network (of 20/25 nodes, 90% S7-400 series), to diagnose communication/process issues, having simultaneously open·connection to 4/7 of them. Once (during vacations) I did it from the beach under a big umbrella with the laptop through gprs connection (umts was not available in the place "CaboVerde": yes, my notebook is 24/24-7/7 with me). The feeling was like being on the customer site
BTW I am still using the PI S5 programming platform (a dated release) if·I can (not all expansion cars/high level cpu's supported) because is a Windows app. Siemens have ported it from CP/M to MS-DOS (last release 7.22) running under XP/Win2k without problems but still a MS-DOS app. Every programmer knows how important is cut&paste feature and/or multiple source-windows opened simultaneously,·for example. Sometimes I use it to write·code also for unsupported systems, then I open it with Siemens software, integrate the missing things and transfer to the plc.
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