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Reading RPM from encoder

Created by: adrian_botez at: 6/27/2014 1:34 PM (23 Replies)

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6/27/2014 1:34 PM	Rate (0)
adrian_botez Bronze Member Joined: 2/19/2013 Last visit: 10/6/2024 Posts: 185 Rating: (9)	Hello. I have an encoder that have 2500 PPI. How can I calculate the RPM of the motor using the encoder ? I know that with every turn the engine travels 817mm, so with every pulse i travel 0,3268 mm. I have to take this in count when I made the calculation? What formula do I have to use?

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6/27/2014 2:57 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, Count pulses per second, multiply with 60, devide the result by 2500. What PLC do you have? And what countercard? Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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6/27/2014 3:13 PM	Rate (0)
adrian_botez Bronze Member Joined: 2/19/2013 Last visit: 10/6/2024 Posts: 185 Rating: (9)	I want to do it with a 1214 CPU (maybe) or with a 317 2DP. The advantage of the 1214 are the integrated HSC. It can be done with the 1214 also, right? But I don´t understand one thing. The encoder wil give me a value from 0 to 2500 everytime it turns ? Or it will add values over and over again?
	Last edited by: adrian_botez at: 6/27/2014 3:22 PM
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6/27/2014 3:31 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, The encoder will give you 2500 pulses per revolution. Yes, you can use the 1200 plc, set the HSC to frequency measurement. You can then set a time interval, read the measuered value and calculate RPM. Formula is= measuered value / time interval * 60. I think if you use the search field at the top right corner, you may even find some examples. Regards, Marcjan
	Last edited by: Marcjan at: 6/27/2014 3:33 PM Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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6/27/2014 3:56 PM	Rate (0)
adrian_botez Bronze Member Joined: 2/19/2013 Last visit: 10/6/2024 Posts: 185 Rating: (9)	But where I can see the value of counting? Because it depends of the cyclic OB, the scan cycle, and the value wil not be the real one.

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6/27/2014 4:48 PM	Rate (0)
William_B Posts: 5225 Rating: (1192)	adrian_botez But where I can see the value of counting? Because it depends of the cyclic OB, the scan cycle, and the value wil not be the real one. Easy Book Manual, 03/2014, A5E02486774-AF Use the high-speed counters (HSC) for counting events that occur faster than the OB execution rate. .... You configure the parameters for each HSC in the device configuration for the CPU: counting mode, I/O connections, interrupt assignment, and operation as a high-speed counter or as a device to measure pulse frequency. Attached some homework. w Attachment EXTRACT_Easy Book Manual (A5E02486774).pdf (1917 Downloads)
William_B Posts: 5225 Rating: (1192)
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6/28/2014 3:21 PM	Rate (0)
adrian_botez Bronze Member Joined: 2/19/2013 Last visit: 10/6/2024 Posts: 185 Rating: (9)	Yes, I have read this example before, bt it´s not 100% clear. There are a lot of examples here, but al of them only bring me to confusion.

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6/28/2014 3:29 PM	Rate (0)
William_B Posts: 5225 Rating: (1192)	Adrian, We understand your frustration.. believe it or not this forum do want to help. There is a fine line in doing the job for you and educating. I will be most grateful if you can identify what it is you are having difficulty with. Maybe make some small program and publish it here. Then we can turn this arround into a Q&A where we (this forum) can work from your example. Please help me to help you. Supply us a solid starting point to work from. w
William_B Posts: 5225 Rating: (1192)
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6/28/2014 3:51 PM	Rate (0)
William_B Posts: 5225 Rating: (1192)	As a show of good faith to you, I am willing to give you a push. I am unsure on where your experience level is, so forgive me if I give you info that is trivial to you. Please see attached x3 PDF files zipped ~~in a password protected file~~. ~~I will send via private message the password.~~ Please work through these. Then create a TIA project that uses an S7-1200 PLC. Enable and set up in the hardware configuration one of the HSCs. Next make a call with the "CTRL_HSC" inside OB1. Write variables inside this block what you think you need. Publish the project file here (without password please). State for us which HSC you have used. After this we will give you indications on how to use the HSC with some maths. I hope to receive your positive response. w Attachment HSC_notes.zip (1482 Downloads)
William_B Posts: 5225 Rating: (1192)	Last edited by: William B. at: 6/28/2014 10:06 PM Password removed from ZIP file.
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This contribution was helpful to 2 thankful Users bobo2015 Engea

6/28/2014 9:31 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, @ william, why using passwords? This is a public forum, if you have information that can help, share it. If sharing the information can harm you, because of company rules just don't share. Publishing here password protected files does not help the community just the one person you send the password to. If you like to send files that not can be read by anyone, don't use the forum send it by pm or i.e. wetransfer. No offence, And regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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