Sign in to follow this  
Followers 0
jeffellis1

Learning Siemens

8 posts in this topic

I'm proficient with AB PLC's but occasionally receive inquiries from job offers about Siemens. Can anyone point me in the right direction with either a website, some software or how can I learn Siemens PLC's? I haven't had the chance to even see the Siemens software ladder logic or anything about them, so any help is greatly appreciated. Thank you, Jeff

Share this post


Link to post
Share on other sites
There is a short tuturial that comes with the Step 7 software that can give you a jump start. Programming in Step 7 ladder is similar to programming in RSLogix. Actual h/w inputs have a I prefix, actual outputs have a Q prefix, internal coils have a M prefix. The s/w leans toward using tags, similar to ControlLogix, for user defined data structures called function blocks but tags also have a true address (unlike CLX) in the format DBxx.DBy.zz. The biggest drawback is you can't do online edits like you can in RSLogix. While monitoring logic in a subroutine, when you make a change the editor immediately reverts to offline mode. After you've made changes, then you upload the subroutine (FC) to the processor and then you have to go online to see the results. Very cumbersome and slow. I put temporary bits inline with my changes so that I can enable the changes after going back online. Then I can test the changes in real time. I'm sure there is more to know, but I've only done 4-5 Siemens projects in the last 3-4 years and that much knowledge has gotten me through. -Jeff

Share this post


Link to post
Share on other sites
Jeff I know how you feel. I to am confident in RS logix and DeviceNet communications but going through the same trouble converting to Siemens which my new employer are installing. I recently attended Siemens training courses in Step 7 and PCS7 and find S7 does not have the same structure and lacks alot of the functions you may have taken for granted in A.B. One of my biggest gripes is as we are used to programming in ladder, programers now have the option to use Ladder, Function Blocks or Statement list and Statement list is find is a problem, each type of code written can not always be translated into another otherwise we could happily convert it to ladder. I've not really come in contact with Profibus which my new comms network and could do with any help from anywhere on that. With it being 2 core cable unlike DeviceNet in 5 core, is the comms signals sent through with the 24v and GRND cables to the ASI modules and how is the structured. All help on S7 PCS7 and Profibus will be greatly appreicated to get us of the starting blocks Cheers Mart

Share this post


Link to post
Share on other sites
Hi, new guy here. I just started a fairly good sized project that uses all Siemens components. After 20 years of AB, it's my first time with Siemens. I realized I needed to learn STL to be able to do much with it. You really can't do as much in ladder/FBD as you can in STL, namely indirect addressing. The processor is pretty cool. It's a CPU317T-2 DP. It has two Profibus channels, one for I/O and HMI and one for motion control(DP Drive). I'm using the S7 technology add on software package that enables integrated motion control of up to 32 axis. I've spent the last month learning STL and I think I can get what I need with it now. It's kinda similar to assembly. Everyone said once I learned it I would love it. At first I was like, Wow, this blows! Now I actually do like it. I'm totally biased toward AB, but I like learning new processors and so far I give this one a thumbs up.

Share this post


Link to post
Share on other sites
jeff: The biggest problem with S7 is the documentation. There is so much of it, and it tend to confuse rather than aid in the understanding. For a beginner the best approach is: 1. Get an introductory S7 course. It is money well spent; in particular if you have a deadline. 2. When you get back from the course get an S7 "testbed" with a small PLC to play with. Start fooling around with it. 3. When (not if) you get to a question or problem, do not hesitate to ask - either here on this forum or at Siemens support, they generally come back with helpful replies even for "stupid" questions. mart: Profibus is RS485 and so is Devicenet. I think that Devicenet uses the extra wires to supply sensors or to provide voltage for the termination resistors (not sure which is correct). The actual datatransfer happens on only two of the wires, thats for sure. If you have Profibus and ASi, then there must be a Profibus/ASi converter somewhere in the middle. ASi has its own electrical standard (not RS485). For the S7 CPU the Profibus/ASi converter appears as one Profibus slave node. In the end it means that all the ASi nodes appears as an I/O area in the S7 program. If you have a particular question then do not hesitate to ask.

Share this post


Link to post
Share on other sites
Thanks Jesper, Your right by the way in what your saying about DeviceNet being 5 cores by way of 24v,0v, drain along with Can-H and Can-L as the comms. One other problem I've just stumbled upon is the different procedures in searching for an address, at present I'm looking at code written as STL in S7 and to go to an address I open up an FC, right click to "go to / loaction", then type in the address I'm after. But in function block code how do I search for an I/O address if I don't know where is it and is it different when using PCS7. Can you give me any pointers on quick searching for addresess

Share this post


Link to post
Share on other sites
STL, LAD and FBD work in the same way with respect to "quick search". Highlight an address and hit CTRL+ALT+Q to search globally for it. Check the "overlapping access to memory areas" option. It will provide more information than the default without this option. So how to search for an address that you cannot see right away ? Answer: Just highlight any other address and use CTRL+ALT+Q, then in the dialog box change the address to the one you are looking for. And yes, silly of Siemens not to allow us to use CTRL+ALT+Q without first selecting an address. They could just have opened the dialog box without an address specified. edit: I have never worked with PCS7, so I cant tell if it works differently. Edited by JesperMP

Share this post


Link to post
Share on other sites
Dear Mr, Let us know which model PLc of Siemens you would like to learn S5/S7 Regards N.Subrahmanyam iic_hyd@rediffmail.com

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0