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Reading Real Time RPM using proximity Sensor and S7-1200

Created by: Muhammad Haris at: 12/2/2014 12:37 PM (13 Replies)

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12/2/2014 12:37 PM	Rate (0)
Muhammad Haris Posts: 19 Rating: (0)	Greetings, I want to read real time RPM using s7-1200 TIA Portal. I previously tried reading pulses for 1 sec and multiplied it with 60 to get RPM but the issue is the variation that occurs is of 60. I studied about it and the best solution that appeared to me was caluclation running sum of the pulses for 60 sec in that way the reading will be real time and variation will be of 1-2. Issues is I can only find its implementation in STL. S7-1200 is only supporting LAD/FBD. How should I do it?
Muhammad Haris Posts: 19 Rating: (0)
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12/2/2014 1:25 PM	Rate (0)
miami Platinum Member Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (328)	The (actual) S7-1200 CPUs can be programed in SCL. (Maybe the first ones with FW <2.0can't use SCL)

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12/2/2014 1:35 PM	Rate (0)
Muhammad Haris Posts: 19 Rating: (0)	How to enable SCL? I am getting just LAD/FBD option in TIA potal V12 I am seeing Firmware to be 3
Muhammad Haris Posts: 19 Rating: (0)	Last edited by: Muhammad Haris at: 12/2/2014 1:38 PM
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12/2/2014 1:58 PM	Rate (0)
Muhammad Haris Posts: 19 Rating: (0)	Available Options are as in the picture Attachment 12.jpg (724 Downloads)
Muhammad Haris Posts: 19 Rating: (0)
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12/2/2014 2:19 PM	Rate (0)
eisenpferdreiter Posts: 1058 Rating: (93)	Muhammad Haris Greetings, I want to read real time RPM using s7-1200 TIA Portal. I previously tried reading pulses for 1 sec and multiplied it with 60 to get RPM but the issue is the variation that occurs is of 60. I studied about it and the best solution that appeared to me was caluclation running sum of the pulses for 60 sec in that way the reading will be real time and variation will be of 1-2. Issues is I can only find its implementation in STL. S7-1200 is only supporting LAD/FBD. How should I do it? Hello Muhammad Haris, I would provide a buffer for 60 values that represent pulses per second in FIFO principle (first in, first out). Latest value in would always overwrite oldest value in buffer. Thus when you sum up the buffer, you will always have a valid RPM value at every second - with the first valid value after one minute. regards
eisenpferdreiter Posts: 1058 Rating: (93)
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12/2/2014 2:19 PM	Rate (0)
miami Platinum Member Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (328)	You have to select SCL when adding the block in the program blocks folder. It's not possible to change between SCL and LAD/FBD after the block was added. Attachment D:\1.jpg (528 Downloads)

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12/2/2014 5:14 PM	Rate (0)
Muhammad Haris Posts: 19 Rating: (0)	Thank you. Worked but can't SCL be coverted back to LAD/FBD?
Muhammad Haris Posts: 19 Rating: (0)
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12/2/2014 5:22 PM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Muhammad Haris Available Options are as in the picture Hi. Follow the direction given by Miami. What you need to do is create a new Function Block (FB) or Function (FC), then select what language you wish to use. Just remember to call the FC or FB in OB1 later on (I still forget to do that sometimes). Using SCL is not going to give you the solution. SCL will help if you are comfortable with coding in Pascal, C, Java, .. Working with LAD is still an option to you. eisenpferdreiter has a good option for you. It is a type of a counter with memory. For example you can have an update every 10 seconds and store the last 6 counts. Every 10 seconds you add a new value and take away the oldest value. Do you know how to work with arrays? Other alterantives exists. There is the option of measuring the time between pulses and project how many pulses you will get in a minute. The best way to make this work is to use a interrupting function on the triggering input. Then have a timer run between the triggers. The problem is the accuracy of the timer.. unless you use unconventional timing. (so better we ignore this one) The next option is to use the built in high speed counter (HSC) and use the frequency measurement option. With this option at least you are not bound to the cycle time of the PLC which will be a problem in other methods. Again you can build up a buffer of readings over the minute. Now I think you might have some questions.. please feel free to ask - someone should answer. Cheers. w
William_B Posts: 5225 Rating: (1197)
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12/2/2014 7:02 PM	Rate (0)
miami Platinum Member Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (328)	Muhammad Haris But can't SCL be converted back to LAD/FBD? In STEP 7 V5.x the SCL compiler and the FBD/LAD editor generated STL code. But this code was more or less"unreadable" for humans (e.g. without any structure and comments). In TIA Portal all programming editorsdirectly generate the machine code for the PLC (Without generating STL first)

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12/2/2014 9:01 PM	Rate (0)
William_B Posts: 5225 Rating: (1197)	@Muhammad Haris: I hope to direct your attention to: [LINK] Special attention to time stamps.. 5/31/2014, 10:42 PM 6/2/2014, 8:57 PM 6/2/2014, 10:57 PM You may find it useful in your quest. The first date stamp discusses the concept of moving average which may be helpful to you when you are measuring frequency of pulses. Also included is background information on how the rotary action of values in an array works. I hope this is of value to you. w
William_B Posts: 5225 Rating: (1197)
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