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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 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?
adrian_botez Posts: 185 Rating: (9)
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6/27/2014 2:57 PM	Rate (0)
Marcjan Diamond Member Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating: (716)	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 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?
adrian_botez Posts: 185 Rating: (9)	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 Diamond Member Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating: (716)	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 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.
adrian_botez Posts: 185 Rating: (9)
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6/27/2014 4:48 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	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 (2749 Downloads)
William_B Posts: 5225 Rating: (1204)
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6/28/2014 3:21 PM	Rate (0)
adrian_botez 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.
adrian_botez Posts: 185 Rating: (9)
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6/28/2014 3:29 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	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: (1204)
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6/28/2014 3:51 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	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 (1960 Downloads)
William_B Posts: 5225 Rating: (1204)	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 Diamond Member Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating: (716)	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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6/28/2014 10:11 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	Marcjan ... This is a public forum, if you have information that can help, share it. ... okay, password removed.
William_B Posts: 5225 Rating: (1204)
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6/29/2014 7:20 PM	Rate (0)
adrian_botez Posts: 185 Rating: (9)	Thanks you for the documets in the PDF. Very useful. I´ve made the program some sort of this. But I don´t understand how you will calculate the RPM. If I don´t want to use frequency , how do I do it? Attachment encoder.zip (1187 Downloads)
adrian_botez Posts: 185 Rating: (9)
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6/29/2014 8:48 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	adrian_botez Thanks you for the documets in the PDF. Very useful. I´ve made the program some sort of this. But I don´t understand how you will calculate the RPM. If I don´t want to use frequency , how do I do it? ¡hola amigo! Gracias por sus comentarios. The file your sent is a good starting point. In my next message I will answer your question. Please expect that soon. It is very important that we get the baseline set. With the attached ZIP, I am trying to close the gaps left by the previous files I left you. Please make that part of your project. I'll talk to you agin in a few minutes. w Attachment A001.zip (1032 Downloads)
William_B Posts: 5225 Rating: (1204)
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6/29/2014 9:10 PM	Rate (0)
adrian_botez Posts: 185 Rating: (9)	Thanks you. But if I read the value in my normal OB1 scan, I will not get real values, I have to read it with :P. That is right?
adrian_botez Posts: 185 Rating: (9)
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6/29/2014 9:24 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	adrian_botez Thanks you for the documets in the PDF. Very useful. I´ve made the program some sort of this. But I don´t understand how you will calculate the RPM. If I don´t want to use frequency , how do I do it? Adrian, I should mention that what we are doing here will (probably) solve the question you started wit for this theme. I have no guarantee that it will help you with your actual application problem. The frequency measurement that the HSC can provide is actually very helpful for working out the RPM. We will attempt another approach however. [background] The HSC you created is a continuous counter. Each pulse the encoder gives, the HSC will count. If your program does not interfere, the value will continue growing. Some encoders have a zero mark signal. You can register this signal into the hardware definition which will cause the HSC to zero at each revolution. Careful: The A/B pulse encoder set up will give x4 the value of your encoder for each encoder revolution. So if the encoder is rated 2,500 the HSC will increase by 10,000 counts for every encoder revolution. [program addition] In the next step we will add a cyclic interrupt OB30. OB30 will grab the value of the HSC at regular precise intervals. You have to decide for yourself how long this period is. The longer the period, the more accurate the measurement but also slower the reaction. Hints on creating OB30 is given in the JPEG. For argument we keep it at 100ms time. Also create three global variables from memory: BUFFER1, BUFFER2 and DIFFERENCE of type DINT. Now you can create code inside OB30 to do the following tasks: 1. %ID1000 -> BUFFER2 1. BUFFER2 - BUFFER1 -> DIFFERENCE 2. BUFFER2 -> BUFFER1 DIFFERENCE is the count of encoder pulses that was counted by HSC1 within 100ms. We now know that there are 10,000 pulses for each encoder revolution (2,500 x 4). Then also 1min = 60sec = 60,000ms or 600 x 100ms. So you can create this code inside your normal program.. RPM_ENCODER = 600 x DIFFERENCE / 10,000. Remember.. * the "600" depend on what you set the update time for in OB30. * 10,000 depends on what encoder you use and what you set it for * RPM_ENCODER is a REAL number. You may need to convert DIFFERENCE to a REAL number. Finally.. RPM_ENCODER is the RPM of the encoder. RPM of the motor depends on where you mount the encoder in relation to the motor.. in other words.. how many revolutions of the motor is how many revolutions if the encoder. If you give us more info on how the encoder is mounted we can help there. --- Please look at the previous post about the creation of the HSC. Then create the coding as listed above. Then please publish your project for me, or another member to make comments. Please ask questions after you have done this exercise. Greetings. w
William_B Posts: 5225 Rating: (1204)
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This contribution was helpful to 3 thankful Users luciferC4 tony311 wiks

6/29/2014 9:33 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	adrian_botez Thanks you. But if I read the value in my normal OB1 scan, I will not get real values, I have to read it with :P. That is right? Yes you are right. BUT.. The scan of OB1 is so "slow" when comparing with HSC, that reading ID1000 as is, is better. Within one scan of OB1 you do not want the inputs to change.. this can cause problems for your coding. Each time you use the :P, the value would have changed. Using %ID1000:P inside the interrupt is okay. This is not a fixed rule however.. this is my technical opinion. Also never try to do.. %ID1000:P ----\| = \|----- "value" your code will have a possibility of missing the "equal to" position. Better to use a compare within two limits.. the two limits does not have to be far apart. w
William_B Posts: 5225 Rating: (1204)
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6/30/2014 3:03 PM	Rate (0)
adrian_botez Posts: 185 Rating: (9)	OK. This week I will try it and the resut will be posted here.
adrian_botez Posts: 185 Rating: (9)
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7/25/2014 2:02 PM	Rate (0)
adrian_botez Posts: 185 Rating: (9)	I have done all this configuracion, but I dont have any response from the encedor. If I move the encoder slowly I get values incrementing one by one. Bt if I do it fast, I don´t have any answer. It doesn´t count. What can I do?
adrian_botez Posts: 185 Rating: (9)
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7/25/2014 2:20 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	adrian_botez I have done all this configuracion, but I dont have any response from the encedor. If I move the encoder slowly I get values incrementing one by one. Bt if I do it fast, I don´t have any answer. It doesn´t count. What can I do? Welcome back. Please check the filter timing of your digital inputs. These are set to a too high value. See the JPEG. Do let us know the result. Greetings. w Attachment Visual clue_Where to find filtering times for inputs.jpg (1097 Downloads)
William_B Posts: 5225 Rating: (1204)
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7/28/2014 9:31 PM	Rate (0)
adrian_botez Posts: 185 Rating: (9)	Great. That was the issue. Thx!
adrian_botez Posts: 185 Rating: (9)	Last edited by: adrian_botez at: 7/28/2014 9:31 PM
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This contribution was helpful to 1 thankful Users William_B

7/28/2016 1:01 PM	Rate (0)
Okod Posts: 38 Rating: (0)	Hello Guys, The file encoder is not working with me as it has different ext. can anyone resend it to me again please. Regards.. Okod
Okod Posts: 38 Rating: (0)
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7/28/2016 1:15 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	Okod Hello Guys, The file encoder is not working with me as it has different ext. can anyone resend it to me again please. Regards.. Okod In the ZIP is a "ZAP13" file. This is an archive for a TIA Portal V13 project. Unzip this ZAP13 archive......
William_B Posts: 5225 Rating: (1204)
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This contribution was helpful to 1 thankful Users Okod

7/28/2016 1:29 PM	Rate (0)
Okod Posts: 38 Rating: (0)	Thank you William now it works. Regards.
Okod Posts: 38 Rating: (0)
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5/22/2018 10:36 AM	Rate (0)
Jen_Moderator Posts: 8171 Rating: (174)	New question published by AFMA7827 is split to a separate thread with the subject Big problem with speed measuring using as5045 encoder. Best regards Jen_Moderator
Jen_Moderator Posts: 8171 Rating: (174)
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