# Siemens S7 200

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#### Simone Stefani

Hello list, i should be happy to know what do you think about S7 200. I think that Siemens did one step back with "System 200" vs. "System 300"
and "System 400". I mean the instructions set and the possibility of program structuring are lesser performing in the first system than in the other two.

Simone Stefani
Automation Dep.
Romaco Zanchetta
Tel. +39-(0)583-2171
Fax +39-(0)583-217317
e-mail: [email protected]

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#### Mark Hutton

The S7-200 is a micro PLC.

It is intended to be cheap and simple to use. To that end it is succesful (fairly), the 200's are good for their target market (small machine control etc.). The Step7-Micro is easy to pick up and has few foibles.

The 300/400 lines are fully featured PLCs suitable for a wide range of applications, suitably complex and with a suitable price tag. I haven't looked too deeply at the full step 7 product but I can tell you that I had my first 200 project programmed in about the same time as it took my to realise that I wasn't going to just click and go with Step7.

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#### roger Irwin

I think it is deliberate. The 200 is not a Siemens developed product, it was done by TI and they later purchased it. The 200 is very powerfull for the price, and we would use it in a lot more applications were it not for the fact that a) it does not have removable connector blocks and b) You cannot structure the software very well.

The limitation is not caused by the PLC, but by the MicroWin development software. At first I thought it had been written by idiots, but then I realised that they had very carefully eliminated anything that you may use as a workaround to get something more symbolic (you cannot even assign an arbitrary value to an arbitary symbol, as you can with even the most primitive of assemblers). I think they do this to force you onto more expensive hardware for more complex problems.

Of course Siemens charge you $2000 (plus NDA) just to get the comms spec, let alone reveal other information that might allow somebody to develop an alternative development tool. Is there any sort of law against this? As a hardware box, I think the 200 is great, all it needs is removable terminal blocks and perhaps a few more I/O modules, but that development environment is a real handicap. At least it is for free......perhaps that is part of the strategy! D #### Dave Cooke I've just finished coding a development project using the (bottom of the range) S7-210 version. Originally we were going to knock something up using veroboard and cmos gates. Lucky we didn't as there have been so many changes to the specification. The S7 is a nice small size - easy to mount in a box for our project to go out for field trial. I don't think it's meant to rival the 300 and 400 series. The two down sides I've found with the 210: * You only have 4 counters and 4 timers. I suspect that this is an intentional limitation for marketing purposes, which is annoying but typical Siemens. * Only 4 inputs for 4 outputs. This was a struggle. Typically you usually have more inputs than outputs in a system. DC PS - Thanks to M.Mogford / M.Griffin / McQueen / Rodrigo for your advice and offers to help with my program. M #### Mauricio Robles -I think it is no step back, but it sure is a very good an inexpensive method of getting small automation. G #### Gary Hoskins Something to remember with the S7-2XX Family is it was designed as a Micro PLC used in smaller applications. By design a Micro is less expensive and the Programming Software is generally not as elaborate. This keeps the cost down to make this PLC available at a much lower cost for small applications. I work for a Municipal Utility in North Florida and when our Project is finished we will have over 600 S7-216's installed running WasteWater Lift Stations. I do consider myself a very capable programmer as I wrote the RTU Program with the exception of the Modbus Slave subroutine which was supplied by Siemens in the form of an application tip. Having said that I find the S7-2XX is a very capable PLC with its major limitation being Discrete I/O. This PLC has a lot of power for such a small PLC. This PLC has the capability to do 8 PID loops onboard. I formerly used the SyMax mid range PLC which were much more expensive and you had to do special programming to do any PID loops. I also will use the S7-3XX Processors to control the Larger Lift Stations. This is the Siemens mid range PLC. It definitely has more capability, naturally the Programming Software is more complex and expensive. We also use S7-4XX as Data Concentrator's to poll all the Remote RTU's using the Modbus Master/Slave Poller. This is their large PLC with more capability and complexity than the S7-3XX processors. They definitely will cost you a mint if your application is very large. So before we judge Siemens for the inadequacy of the S72XX family of processors we must remember needs in the market this PLC was designed to meet. These opinions are definitely my own and I am open for comments from anyone who disagrees with them. Gary Hoskins, North Florida. D #### Doug McQueen ESI Electric Supply Inc. The S7200 was developed before the S7300 &400, and brings to the party a price tag very afordable for a expandable brick. By the way, the instruction set is very powerful compared to most other brands with the same price tag. The 200 is built in Germany and the original Micro-Dos was doveloped here in the US. The Software was based around the Ti-soft and GE logic master which goes back before Fanuc days. Now the 300 and 400 both have a spendy (S5-ish) price tag, and this makes sense. The software was not doveloped here in the US, and the hardware is spendy. Yea it better have a more powerful instruction-set. I have worked with Siemens plc,s for over 15 years. Iam familiar with everyone of them, very powerful/dependable. M #### Michael Griffin You need to remember two things. The first is that the S7-200 series is a lower cost PLC than the S7-300 or 400, and it is intended for smaller applications. The second is that the S7-21x series has been replaced by the S7-22x which has a number of improvements including parameterised subroutines and entirely new programming software. I am in the middle of a retro-fit project, part of which involves replacing an Allen Bradley PLC-5 with 4 S7-224 PLCs (this was required in order to accomodate the other changes to the machine). The S7-224 PLCs are being installed in what were the local junction boxes for the AB PLC-5 (no new enclosures are required). Each machine controls a pick-and-place, a resistance welder, a conveyor systems, an RF system, and an operator interface. There is a total of approximately 40 inputs and 36 outputs for each machine. The program sequence has a total of 15 steps (plus repetition of some steps), and a considerable amount of manual diagnostics and control was required for set-up and trouble shooting. My opinion of the S7-200 has improved considerably in the course of this experience. I was at first somewhat skeptical about whether it was a good choice for something this complicated. I have though found it to be easy to use and more than adequate for the job. I did an estimate of what it would take to have done this with an S5-95U by comparing it to another similar, but somewhat mechanically simpler machine which used an S5-95U. I estimate that if I were to use the S7-224 in the machine which currently has the S5-95U, the S7-224 program would be only 40% of the size of the one currently in the other machine, while still having actually more functionality. Given this, I wouldn't have any hesitation about using an S7-224 or 226 in an application where we would previously have required an S5-95U (and we have a lot of these). My own main concern about the S7-22x is the lack of an ASCII or Basic module (the S7-226 does give you an extra port though) for use with bar code readers, programmable instruments, etc. A servo module and a Profibus DP master would be nice too, but not as essential (at least for my applications). ********************** Michael Griffin London, Ont. Canada [email protected] ********************** T #### (TECO) David Bergeron While we're talking about S7-200's, I thought I might mention that Siemens has introduced an upgrade to the S7-21x family called the S7-22x family. They are smaller, faster, more powerful, and completely compatible with the S7-21x programs. I'm not sure if the terminal blocks are removable. They are on the Siemens automation website. David Bergeron, P.E. TECO 504-833-6381 www.thompson-equipment.com D #### D.C. Pittendrigh Hi All I have to come up in support of the Siemens product here !!! > I think it is deliberate. The 200 is not a Siemens developed product, it was > done by TI and they later purchased it. Siemens purchased the TI controls division a good long time before S7 was an established product.... I don't buy this one! >The 200 is very powerfull for the price, Quite true. > and we would use it in a lot more applications were it not for the fact that a) > it does not have removable connector blocks and b) It does have removable blocks, but they have to be ordered separately, not all people like them, I am in this group. >You cannot structure the > software very well. This is a personal problem not an S7 200 problem. > The limitation is not caused by the PLC, but by the MicroWin development > software. At first I thought it had been written by idiots, but then I realised > that they had very carefully eliminated anything that you may use as a > workaround to get something more symbolic (you cannot even assign an arbitry > value to an arbitary symbol, as you can with even the most primitive of > assemblers). I think they do this to force you onto more expensive hardware for > more complex problems. Or perhaps to reduce the cost of the programming software (at around$400 in South Africa)

> Of course Siemens charge you $2000 (plus NDA) just to get the comms spec, let > alone reveal other information that might allow somebody to develop an > alternative development tool. I have a comms spec on this PLC which I payed around$50 for, in the form of a manual on VSD's communicating with the S7200, may be a little obscure if you are looking for a comms spec, but then I was looking for a drives manual, maybe just lucky?

> Is there any sort of law against this?

LOL

> As a hardware box, I think the 200 is great, all it needs is removable
terminal
> blocks and perhaps a few more I/O modules, but that development
environment is a
> real handicap. At least it is for free......perhaps that is part of the
> strategy!

Hmmmmm

Regards
Donald Pittendrigh

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#### Michael Griffin

I've used the S7-22x, and they have a number of improvements over the S7-21x - to the extent that the hardware is not interchangable between the two series. Also, you can load an S7-21x program into an S7-22x, but the S7-22x has features which don't exist in the S7-21x (including subroutine
parameters). You need new programming software (Microwin version 3), and supposedly a new programming cable.

The S7-22x (except for the botton end S7-222) does have removable terminal blocks. Apparently the lack of these on the S7-21x was one of the
biggest complaints customers had (although they did have an optional terminal insert).

However, these new ones are rather cheap removable terminals and are difficult to remove. You would have to be assured that they are there before you would notice them. I was able with some difficulty to remove the terminal blocks on the new 8-in/8-out I/O modules, but you would need more courage than I have to attempt this with the longer terminals on the CPU.

These are are otherwise very nice PLCs. I for one would be willing to pay a bit more money for better removable terminal blocks.

**********************
Michael Griffin
[email protected]
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#### G Ammerlaan

Hi there.

I have a remark about your comment on the 200. The 200 was never meant to "rival" the 300 or 400. The 200 was meant to appeal to the smaller customers. For the development of the 200 they have used some TI technology, you can still see the evidence of this (V memory, one datenbaustein, the way the outputs are connected). With the 22X series, Siemens is trying to turn the 200 in a full Siemens PLC instead of a TI PLC with a Siemens "jacket".

Best regards,

Gerard Ammerlaan

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#### Gerard Ammerlaan

Hi there.
I have a remark about your comment on the 200. The 200 was never meant to "rival" the 300 or 400. The 200 was meant to appeal to the smaller customers. For the development of the 200 they have used some TI technology, you can still see the evidence of this (V memory, one datenbaustein, the way the outputs are connected). With the 22X series, Siemens is trying to turn the 200 in a full Siemens PLC instead of a TI PLC with a Siemens "jacket".

Best regards,
Gerard Ammerlaan