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Cyclic Update on Tag

Created by: Jr. Leow at: 5/28/2007 3:41 PM (4 Replies)

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5/28/2007 3:41 PM	Rate (0)
Jr. Leow Posts: 7 Rating: (0)	Dear all, I am currently assisting one of our client in upgrading the HMI system, from existing Wonderware I touch to SIMATIC WinCC which is connected to 2 Redundant PLC. What i notice is the Wonderware Intouch comes with so called the driver manage which is constantly update all the tags every cycles (e.g. every 1s) This improve their performance when switching from 1 faceplate to another, where all the value is update immediately. While our WinCC system is normally using tag trigger, whenever we switch to a new faceplate, all the tag contains in the faceplate will be update cyclically (e.g update every 2s if we are using tag trigger.) As we change from faceplate to another faceplate, it takes another 2-5s to update the pages with the value again. Any possible that we can write scripts which constantly update the tags and copy the the internal tag for monitoring purpose? Will it creates overload with the system? I project tag size will be <1024 tags. I am also facing some problem with writing tags to SIMATIC S5 (via CP1430 TF) and the tag written is slow. It takes around 10-15s to be able to write in the PLC. Will the cycle time of the PLC will slow down the tag written? The send and receive function block was call every cycle in OB1. Haveyou experience the same problem as this. I look forward for your help. Thank you so much. Best regards, Leow Kien Giap
Jr. Leow Posts: 7 Rating: (0)
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5/28/2007 4:26 PM	Rate (0)
Danielle Posts: 1275 Rating: (123)	Hi Leow, Using scripts to update tags may affect your performance in a negative way. In fact, the more scripts you have running, the more it'll affect the performance. You should whenever possible use tag update cycles. You can change the poll time for the tag update to increase performance. WinCC performance has been discussed many time at this forum. Please search for further information. Here are some of the previous threads: 1, 2, 3, 4. If after searching the forum you still have problems, please post. Best regards, Danielle
Danielle Posts: 1275 Rating: (123)	Last edited by: Danielle at: 28.05.2007 16:30
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5/28/2007 5:11 PM	Rate (0)
Jr. Leow Posts: 7 Rating: (0)	Dear Danielle, Thank you so much for your fast response. I have actually run through all the forum but was unable to find out similar problem like mine. Previously as what customer is having is Wonderware Intouch system connected to SIMATIC S5 unit. What we notice with the performance is, for example, if the is tank level indicated in one of their faceplace, as they switch from pages to pages and then back to the faceplate where the tank level is located, with immediately, he can see the tank level. But, when we implement this case with WinCC, with the same outlook as what Wonderware Intouch is showing, we notice that eventually when we open the faceplate, the tank level will takes 2-3 seconds to display the tank level (most probably was by the tag trigger of 2s was set in the property) but as we change to other faceplate and change it back the the same tank level faceplate, it will required another 2 to 3 seconds before it is showing the actual level. This is unacceptable to customer as they though our new proposed system is slower compare with their existing unit, intouch which was configured in year 95. (10 years old machine) That is the reason i am writing this to constantly pool the date and write it to internal tag, because as it notice, the faceplate pick up the value from the internal tag is much more faster compare to the actual address. Have you face also the problem sending a command to the PLC (SIMATIC S5 via CP1430 TF) is take about 10-15s before the tag is written back to the DB in plc? Thank you. Best regards, Leow Kien Giap (Jr. Leow)
Jr. Leow Posts: 7 Rating: (0)
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5/28/2007 6:18 PM	Rate (0)
Marcio R. Santos Silver Member Joined: 12/5/2005 Last visit: 12/9/2024 Posts: 239 Rating: (9)	Hi Danielle and Leow, Here a conflict lives. I always hear that is better to use cyclical update (configured to 1 or 2 seconds) instead to use upon change update. And sincerely I don't agree with this idea. The WinCC always request the data to PLC in advise mode, the Data Manager only request the data to PLC if the data is necessary, in another cases him don't request. If both cases the data will be request, then, in my opinion is better configured the data by upon change update, because in this mode the dynamics (inobjects andfunctions/actions scripts) only will running once time (when the data really changed). I aggree with you, the best configuration is send the data by exception mode, using Raw Data Tag, but this option is high coast option to only be used in screens. I think that this option is justified to use in Alarm Logging and TagLogging (for severals data by send). We used a typical configuration in our projects, generally are configured 10.000 tag over 10 PLC S7-400, and90% ofdata used in screen and functions are be configured to upon change mode, the Tag Logging is configured to request and storage the data in intervals of 5s (but varies) and Alarm Logging is configured to receive the data from PLC using Message System of PLC. In special case, we sent the data of SOE (Sequential of Events) using B_SEND (Raw Data Tag), where is possible sent until 64kB of data. In this configuration, the update of any object can't delay more than 1 second. And doesn't delay. The only suggestion that I recommend, aided by WinCC Documentation, is: Only use scripts in last case to dynamics objects. I'm not a specialist in PCS 7, but until I know the PCS 7uses scripts strongly in its facesplates, and frequently the programmers configure the update of this objects to cyclical (1 or 2 seconds). Sincerely, I don't know if this is the best configuration.
	Last edited by: Marcio at: 28.05.2007 18:21 Márcio Santos www.marcioroberto.wordpress.com
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5/28/2007 6:38 PM	Rate (0)
Danielle Posts: 1275 Rating: (123)	Hi, We usually use tag triggers, with upon change polling rate... but I've seen cases at the forum where users claim that using a 1s poll increases performance... Leow... you should try changing the poll rate. 2 seconds seems to be too much for what you need, so you should try less time (e.g.: 1s, upon change) and see if it suits your needs. If changing the oplling rate doesn't help you must check if your problem is really in the triggers, 'cause something else could be causing the performance issue, as you've seen in the other threads. As for the commands, I've never used S5 channel, so I can't help you with that. All I can say is that I haven't seen users complaining of 15s delays. Best regards, Danielle
Danielle Posts: 1275 Rating: (123)
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