Industry Online Support
Technical Forum
Navigation
Rating 
Thanks 4
| 6/9/2011 6:24 PM | |
Joined: 8/31/2005 Last visit: 8/20/2024 Posts: 2198 Rating:
|
Just to make it clear, Amit_86was talking of a CPU 314Cbut venkatvetriwrote CPU 314 (without C) The compact CPUs (313C and 314C ) have a builtin I/O to read in pulses. The normal CPU you may use a FM350 or a 1PULS in a ET200. To use a normal I/O card is not recommended |
|
|
|
| 6/9/2011 6:54 PM | |
|
Posts: 947 Rating:
|
If the pulse rate is very low, you can use a digital input with interrupt for direct pulse counting, but it is better to use the hardware as said miami |
| 6/11/2011 12:53 PM | |
Joined: 5/28/2008 Last visit: 9/9/2024 Posts: 4515 Rating:
|
Hello, If you are talking about CPU314C, then yes you can and the following FAQ will answer you Configuring the "Signal evaluation:" parameter in 31xC CPUs using the technological function "Count" Hope this helps. |
Last edited by: Ayman Elotaify at: 6/11/2011 12:57 PMLast edited by: Ayman Elotaify at: 6/11/2011 12:54 PMAyman Elotaify |
|
This contribution was helpful to
|
|
| 6/11/2011 1:18 PM | |
|
Posts: 947 Rating:
|
in additonal to postAyman Elotaify useful link for compact CPU http://support.automation.siemens.com/WW/view/en/33519671/130000 with sample: http://support.automation.siemens.com/WW/view/en/18467424 |
Last edited by: gre_m at: 6/11/2011 1:20 PM |
|
This contribution was helpful to
|
|
| 6/11/2011 4:38 PM | |
Joined: 10/7/2005 Last visit: 9/16/2024 Posts: 3020 Rating:
|
Hello Narayanaswamy while you received a fair bit of well meant advise on how to make this work, I suggest you firstly checkwhat the maximum rpm is in your application. If it is more than 10rpm you can pretty much forget using normal DI's for counting and the reason for this is: (360 ppm * 10 rpm) / 60 sec/min = 60 pulses per second (or one pulse every 16.67 ms). A "pulse" in this context means a wholeON/OFF cycle so you'llhave a 1 signal for some 8ms and a 0 signal for some 8ms. A normal DI card needs anywhere from 1.2 toto 4.8ms to register a 0-1 or1-0 transition, so it will bejust fast enough to realiably detect an 8ms long pulse. You additionally need a cycle time faster than4ms or call a cyclicinterrupt OB every 4 ms to raliably evalute the pulses and do the counting (worst case is 4.8 ms 0-1delay and 1.2 ms1-0 delay in which case you only "see" the input ON for some 4 ms in your program). You'd be able to count a bit fasterif you use a hardware interrupt and OB40 as suggested by Ayman Elotaify. In that casethough you must use a hardware interrupt capable DI cardand can NOT use a normal DI card. My advise: Stick with miami's advise and use a high speed counter card, it is the only sensible thing to do. I hope this helps |
|
Cheers |
|
| 6/10/2020 10:37 PM | |
Joined: 3/9/2018 Last visit: 8/31/2024 Posts: 189 Rating:
|
Are you sure this error is not created by mechanical slack? |
This contribution was helpful to
|
|
Follow us on