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Speed measure with FM350 and 500 ppr encoder

Created by: one2three at: 6/20/2007 7:19 AM (13 Replies)

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6/20/2007 7:19 AM	Rate (0)
one2three Posts: 37 Rating: (1)	Hi How do I measure speed using a FM350 module? I got the pulses but they dont tell speed are there any FC for converting pulses into speed? Best regards
one2three Posts: 37 Rating: (1)
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6/20/2007 10:26 AM	Rate (0)
Aret Posts: 2348 Rating: (264)	You can see how FM350 configured in this manual http://support.automation.siemens.com/WW/view/en/2742764. To make FM350 counting rotation speed you will need special configuration package - it's supplied with FM350. If you have more defined question/problem - i'll bу glad to help you :)
Aret Posts: 2348 Rating: (264)
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6/20/2007 2:04 PM	Rate (0)
one2three Posts: 37 Rating: (1)	I'm not sure ifI got the right software and hardware that is needed. My cpu is a 315-2 DP (315-2AF03-0AB0) and my counter modul is a FM350-1 (350-1AH01-0AE0). also my encoder is a Leine & Linde Part no: 517890-05 / 500ppr. My software is the latest simatic manager version and Version 5.1 of the conuter software. I'm including a screenshot of the choises thatI got in the counter software. As I understand I should be able to choose "RPM Mesaurment" with that tool but I cant find such option in my software. Also .. db1.dbd34 isnt counting up, it's just flashing between 0/1 when axis is moving. Thanks in advance Johan Attachment fm350-1.pdf (376 Downloads)
one2three Posts: 37 Rating: (1)
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6/20/2007 3:16 PM	Rate (0)
Aret Posts: 2348 Rating: (264)	To be honest i've never configured FM350-1. As i can understand it's different from FM350-2 (My screen "operating modes" has ability to choose RPM, but it differs from yours. You can try to read about Fm 350-1 here -http://support.automation.siemens.com/WW/view/en/1086726. There is description how to make RPMcounting. Not sure, but i think yourproblemisingatemode-tobemoredefinedihavetotakecloselook.
Aret Posts: 2348 Rating: (264)
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6/20/2007 6:23 PM	Rate (0)
SteveA Posts: 297 Rating: (41)	I've never used the FM-350, but a quick look at the catalog leads me to belive that you need the FM350-2 if you want to measure speed. The -1 only counts. If you had to, youcould caculate the speed yourself by keeping track of the change in count over a fixed time period. Your description of the counter displaying only 0 or 1 sounds like one of the inputs is not connected or working. You need both A and B signals in quadrature for the counter to work at all. Hope this helps, SteveA
SteveA Posts: 297 Rating: (41)
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6/21/2007 11:26 AM	Rate (0)
one2three Posts: 37 Rating: (1)	Thanks alot SteveA, it was the b channel that wasnt connected, now it's counting up. How is it possible to make a own program to measure speed with FM350-1 or is there a already working solution free for download? I feel thatI dont have to skills to make one myself. Again thanks for the help.
one2three Posts: 37 Rating: (1)
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6/21/2007 11:57 AM	Rate (1)
Thijs Posts: 121 Rating: (16)	In the newest version off the FM350-1 it has become availeble as an standard function (measuring) For an older version I think you have to solve it with software. A good thing to to is to make this function in a cyclic interrupt (OB35 on 10ms) and read the PIW data from the OB35. By looking at the difference in counts you can calculate the distac traveld in a sertain time. (== speed)
Thijs Posts: 121 Rating: (16)
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6/21/2007 12:50 PM	Rate (0)
one2three Posts: 37 Rating: (1)	How do you mean read PIW from OB35? Would you like to make a small sample for me and upload? Thanks in advance
one2three Posts: 37 Rating: (1)
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6/21/2007 3:10 PM	Rate (1)
Thijs Posts: 121 Rating: (16)	The following code is from the top off my head, I haven't tested it. But you should get the general idea. You should look in the HW-config for the actual PID number (I've used PID256) Please look for the PID number that contains the actual value. [code] // Calculate the distance traveld L PID256 // actual count value L MD200 // old count value -D // difference T MD204 // Distance traveld in OB35 scantime // Convert to speed L MD204 DTR // Change to REAL value L 12.71 // counts per mm /R T MD208 // The actual speed // Save the actual value for the next time L PID256 // actual count value T MD200 // old count value[/code] Depending on the speed you want to measure and how often the speed changes I would recomment a OB35 time that a reaseneble amount off counts is made so a slight difference in count values doesn't change the speed value much.
Thijs Posts: 121 Rating: (16)
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6/22/2007 11:09 AM	Rate (0)
miami Platinum Expert Joined: 8/31/2005 Last visit: 8/20/2024 Posts: 2198 Rating: (328)	Ithink it will not make a big difference, but in my eyes it' s better toload MD402 in Line 15. So you do not loose the pulses coming in during the time the code is running, for your speed calculation.

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