10/7/2008 1:59 PM | |
Posts: 487 Rating: (45) |
S7-200 trip and tricks has some PID examples. http://www.automation.siemens.com/microset/html_76/support/tipps/index.htm?HTTPS=REDIR Also check the FAQs http://support.automation.siemens.com/WW/view/en/7796841 http://support.automation.siemens.com/WW/view/en/27043396 |
10/8/2008 2:53 PM | |
Posts: 11 Rating: (0) |
Thank you Mr JMJ
Ihave benefited greatly from these links, but there are some parts that I do not understand it The Attached file is example program shows how to use PID instruction wizerd Now I want to understand clearly the follwing Points 1-the part of Subroutine ( SBR1 2- The variable memory double word vd154 -vd158 - vd 162 ...... and the rest of variable in the example and no labels or difination for it AttachmentHow to Use the PID Instruction Wizard.zip (350 Downloads) |
10/9/2008 6:24 PM | |
Joined: 4/23/2008 Last visit: 4/25/2023 Posts: 31 Rating: (0) |
Well...let me see if i can help you somehow... 1) The part of SBR1: This is just a subroutine that calculates the average value of the last 4 meditions, so the final value used un the PID control is more accurate having less fast variations (i.e. a digital low pass filter -> reduces noise). Anyway, this calculation is not absolutly necesary in a PID control system, cause you can get same results (maybe best) via "System block"->"Input filtering" ->"Analog". (see Fig1). Also the SBR1 check for errors in the analog modules via SMB8 (search in MicroWin for SMB8 and you will get it) 2) That variable words and doubles VD154, VD158, VD162 (VW156..etc) are just auxiliaries used to get the average value of the analog input. Just that. The VW136 counts the times the temporized interrupt 0 is called (it is called each 100 ms that is the time traspassed to SMB34) (Don't know about timed interrupts? then check this: http://support.automation.siemens.com/WW/view/en/8803785 In the INT0 all the PID calculation is made manually what is really good if you want to learn well and do some stuff and, well, also lose some time. I think the best way to made PID control is via de Operations Wizard, and selecting PID. (see Fig2). Is pretty easy just follow steps to create a nice "box" that does PID control for you, try it. If having trouble look at: http://support.automation.siemens.com/WW/view/en/25781753 Pfeewww ! Well.....guess that's all for now... Hope this helps..and good luck in your PLC quest! Bye! AttachmentFigs.zip (230 Downloads) |
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