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ET200s counting

Created by: laurensvl at: 12/27/2010 1:31 PM (6 Replies)

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12/27/2010 1:31 PM	Rate (0)
laurensvl Posts: 17 Rating: (0)	Hello, We have some old mechanic presetters which we would like to remove and integrate in our plc. To do this, we want to read the input signals over an ET200s station. The maximum speed of the pulses comming in is about 1000/min (the average is 600/min). Is it possible to work with normal digital input cards? What is the best way to read these values so that we are sure we've got every pulse? Should we use a station with a seperate cpu or can we directly read the inputs over the profibus? Other suggestions? many thanks in advance!
laurensvl Posts: 17 Rating: (0)
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12/27/2010 10:57 PM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 3/14/2023 Posts: 928 Rating: (303)	Hello laurensvl, The ability to use of anormal digital input module for 1000 pulse/min depends on your system reaction. The 1000/min gives you a pulseevery 62 msec. If you expect your PLC scan cycle + Profibus cycle time to be less that the 62 msec then you can use standard digital input module. What I recommend is to take the safe side and use the ET200S counter module. By using this module you should be sure not to lose a single pulse. Best regards. H-H

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12/28/2010 11:08 AM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (303)	Hello, I would also go for the ET200S Counter. When using a standard input, you must consider the worst case (to avoid loosing sporadicaly pulses). Some points below that requires attention: Even if a complete pulse takes 60 msec (1000 pulses/min), to be able to count a pulse, you must be able to see the up and the down of it. Let us assume that the pulse is symetric (50% up, 50 % down), you must already detect changes at least at a 30 msec rate. Could be worse if the pulses are not symetric. If you have to transmit a decision back to an output located in a decentralized ET200 (over Profibus), take this also into account. If you also use Profibus for programming, diagnostic, ..., the cycle time of Profibus itself may show some variations depending on what is happening. In the manuals of the CPUs you will find further discussions about response times.
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12/28/2010 12:13 PM	Rate (0)
laurensvl Posts: 17 Rating: (0)	Hello, Thanks for your replies. I have read some documentation and as I see it, you're both right. There are some points though that aren't clear to me. Do these cards keep the counting in an internal memory when they are not polled until the next scan cycle of the profibus? Can you connect them through a standard 151 module or do you need a cpu in the ET200 station? If you use this type of cards for our application, can you use the two channels for a different signal or are these channels always combined into a singlevalue? Is there any special programming required for these cards? thanks in advance
laurensvl Posts: 17 Rating: (0)
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12/28/2010 8:43 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (303)	Hello, Have a look to this manual: http://support.automation.siemens.com/WW/view/en/45977588 Chapter 5 describes the 2pulse module. The two channels of the 2PULSE can be used independently of one another. The chapter describes the programming.
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12/29/2010 10:04 AM	Rate (0)
laurensvl Posts: 17 Rating: (0)	jklm Hello, Have a look to this manual: http://support.automation.siemens.com/WW/view/en/45977588 Chapter 5 describes the 2pulse module. The two channels of the 2PULSE can be used independently of one another. The chapter describes the programming. Hi again, I thought the 2 pulse mode was meant to control 2 outputs and you use the inputs for triggering? Do you know if u can use it with a standard 151 IM?
laurensvl Posts: 17 Rating: (0)
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12/29/2010 10:42 AM	Rate (1)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (303)	Hello, Sorry, my mistake, I was too fast The 2Pulse is for generating pulses, not for counting. For Counting you have in the same manual the Count24V and Count5V modules. Choice is done based on the signal level of the pulses to be counted. Page 9 you see what IM is required as a minimum for the Count24V. Page119 you see what IM is required as a minimum for the Count5V.
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