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Use of Incremental encoder to calculate angle in S7-300

Created by: ashishm at: 6/28/2013 11:54 AM (11 Replies)

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6/28/2013 11:54 AM	Rate (0)
ashishm Bronze Member Joined: 2/1/2011 Last visit: 9/13/2023 Posts: 186 Rating: (4)	Dear Sir, To calculate angle and function machine accordingly, can incremental encoder with ET 200S incoder card be used ???? I assume that 1024 pulse in one revolution of encoder so can be said that for 360 degree it will give 1024 pulse and angle can be calculated. Will this work properly??? Secondly As absolute encoder retains position even after power off. Will my card retains the last value or position in counts format?????

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6/28/2013 1:04 PM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 8/5/2022 Posts: 523 Rating: (32)	ashishm Dear Sir, To calculate angle and function machine accordingly, can incremental encoder with ET 200S incoder card be used ???? I assume that 1024 pulse in one revolution of encoder so can be said that for 360 degree it will give 1024 pulse and angle can be calculated. Will this work properly??? Secondly As absolute encoder retains position even after power off. Will my card retains the last value or position in counts format????? hi, No you cannot use incremental encoder to calculate angle or position so please forget it. absolute encoder are used for actual position and angle measuring in which binaryencoding /gray codeencoding typesare available which will retain position itself eventhough power on/off .no need tosave or memorize position for PLC because when you are making power up the system encoder itself giving exact position in terms of different pattern of binary digit. regards, viral patel

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6/28/2013 1:06 PM	Rate (0)
manmeet Gold Member Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71)	Hi To calculate angle and function machine accordingly, can incremental encoder with ET 200S incoder card be used ???? Yes. I assume that 1024 pulse in one revolution of encoder so can be said that for 360 degree it will give 1024 pulse and angle can be calculated. Will this work properly??? Yes. But since incremental encoder will lose position on power off or when maintenance is done, you have to do homing of the machine. Homing is procedure of bringing machine to a known position from where you start couting the position. Secondly As absolute encoder retains position even after power off. Will my card retains the last value or position in counts format????? Yes it will retain the last position value. Regards Manmeet

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6/28/2013 1:20 PM	Rate (0)
ashishm Bronze Member Joined: 2/1/2011 Last visit: 9/13/2023 Posts: 186 Rating: (4)	Dear viralpatel, For the first time will be using absolute encoder so let me know that encoder on profibus or through card will provide direct angle or pulse count and than we have to process it as angle. secondly please elaborate little that why cant we used the process defined by me. we can do the calculation as told above. Dear manmeet As you said that card will retain the value which means the actual position is retain by me in PLC so after power off and maintenace I still have the value with me so there will not be requirement of home until and unless they rotate encoder in off. I think so same will happen with absolute encoder also(If rotate in power off)

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6/28/2013 1:48 PM	Rate (0)
manmeet Gold Member Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71)	I think so same will happen with absolute encoder also(If rotate in power off) No same thing does not happens with absolute encoder. Even if after you power off PLC / encoder it always gives you reading. Every angle will generate certain set of digital inputs and you just cant loose values. Mechanical guys needs to set absolute encoder properly. Say if machine is tilted at zero degrees then absolute encoder shall give you zero degress only and not some other values. This can be done by resetting the ecoder at zero degrees.Once its set properly you are on your way to operate machine properly. Edit: Once set properly, if you take machine into maintenance and during mainteance (Control panel OFF) machine is moved by 30 degrees and then say control panel is swiched ON, you will get value of 30 degrees in PLC. More about absolute encoder overhere.
	Last edited by: manmeet at: 6/28/2013 1:55 PM
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6/28/2013 1:57 PM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 8/5/2022 Posts: 523 Rating: (32)	ashishm Dear viralpatel, For the first time will be using absolute encoder so let me know that encoder on profibus or through card will provide direct angle or pulse count and than we have to process it as angle. secondly please elaborate little that why cant we used the process defined by me. we can do the calculation as told above. Dear manmeet As you said that card will retain the value which means the actual position is retain by me in PLC so after power off and maintenace I still have the value with me so there will not be requirement of home until and unless they rotate encoder in off. I think so same will happen with absolute encoder also(If rotate in power off) Hi , absolute encoder has more then 10 terminal which you have to connect with DI of PLC and it has fix encoded position set means on 0 to 360 degree it will give binary pulse out to that terminal it give position value so at any position at will give specific fixo/p incaseof encremental encoder it will give pulse as shaft rotating so it will be PLC responsibility to measure it it has nor mally 8 terminal like A/-A,B/-B,Z/-Z and supply wire regards,, viral

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6/29/2013 7:27 AM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 11/6/2024 Posts: 4516 Rating: (839)	viralpatel Hi , absolute encoder has more then 10 terminal which you have to connect with DI of PLC and it has fix encoded position set means on 0 to 360 degree it will give binary pulse out to that terminal it give position value so at any position at will give specific fixo/p incaseof encremental encoder it will give pulse as shaft rotating so it will be PLC responsibility to measure it it has nor mally 8 terminal like A/-A,B/-B,Z/-Z and supply wire regards,, viral Hello, Not all absolute encoders have these specificatins. I think you are talking about a certain encoder. For instance, you may have an absolute encoder on profibus.
	Last edited by: Ayman Elotaify at: 6/29/2013 7:42 AM Ayman Elotaify
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6/29/2013 7:42 AM	Rate (2)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 11/6/2024 Posts: 4516 Rating: (839)	viralpatel hi, No you cannot use incremental encoder to calculate angle or position so please forget it. absolute encoder are used for actual position and angle measuring in which binaryencoding /gray codeencoding typesare available which will retain position itself eventhough power on/off .no need tosave or memorize position for PLC because when you are making power up the system encoder itself giving exact position in terms of different pattern of binary digit. regards, viral patel Hello, I am sorry, I can not agree with you. Incremental encoder can give angle, position and speed if you want. For angle you should have an incremental encoder with outputs A, B and Z. A: channel A, : channel B (A&B) will identify the direction. Z: Zero signal ( 1 pulse each every revolution). If you have incremental encoder with 1024 ppr, then each 360 deg means 1024 pulses. So each pulse means (360/1024) deg. you can monitor it on VAT or HMI. we call this as resolution. If you need more accurite position/ angle, then increase the resolution by buing another incremental encoder with higher ppr. The difference between incremental and absolute is related to loosing position after power failure. So if the power returns, you will have wrong angle for the rest of revolution and after next pulse n Z output f encoder, it will give you the correct angle. And even the power failure problem can be solved now with compact CPUs and FMs. How can the counter values of compact CPUs and of the FM 350 counter module be made available again after a power failure? Hope this helps.
	Ayman Elotaify
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6/30/2013 9:27 PM	Rate (0)
Avinashkrishna Posts: 62 Rating: (4)	Dear Friend, Youcan use Inc Encoder &abt Encoder. but More Prefered is Abs Encoder. Why because in Inc Encoder You need to do Program for Converting the Pules to Angle.Also should Store it in the Retentive menory Or else you need to do Zero Calib. When u Power OFF system. For doing Zero Calib. you need to have the One Proxi Switch. But in Abt encoder you will get the Fixed Pulse for the Rotation.even some encoders can be program for no.pulse for rotation.inc of value in clockwise or anti clockwise direction. if not we need to do the program to convert Pulse to Angle. Regatrds, Avinashkrishna Bhimavarapu.
Avinashkrishna Posts: 62 Rating: (4)	Last edited by: Avinashkrishna at: 6/30/2013 9:31 PM
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6/30/2013 10:21 PM	Rate (0)
AMAZINGAHMED Gold Member Joined: 8/27/2006 Last visit: 10/22/2024 Posts: 719 Rating: (88)	Without doubt, you can use incremental encoder or absolute encoder for accurate positioning. Aboslute encoder can be in different interfaces e.g. profibus, grey code ,etc... Incremental encoder has at least A,B,Z which need to be connected to high speed counter like in CPU31x or FM350 or FM351 When you have a 1024 ppr encoder then every 360 degree will be resembled by 1024 pulse which is a good resolution for motion control applications. Homing (returning to zero) is necessary when you power off then on your PLC, but I think if you save your angle reading to a data block or a retentive range of memory, then it won't be necessary. Profibus absolute encoder has three advantages: 1- saving wiring, specially if you have many encoders. 2- more easy to read the angle in the program. 3- will save the angle after power recycling.
	The more you know, The more you know that you don't know
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