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Encoder reading from S7 - 200 CPU 226

2/17/2011 9:31 AM	Rate (0)
fla Posts: 3 Rating: (0)	Dear Sirs / Madams My application is to read the direction and speed from a motor. I use an encoder with three channels (A, B, Z) and S7 - 200 CPU 226.My though is the follow: Channel A is right direction and channel B is the left direction. So if channel A comes first the motor has the right direction. if channel B comes first the motor has the left direction. If i can measure the period of the pulse i will be able to know the speed of the motor. I know that i should use a high speed counter to be able to read the encoder ( i am thinking of using HSC0 mode 9) but how i will understand which channel came first? For measuring the period of the pulse i am thinking of capture every positive edge of the pulse and inside an interrupt routine subtract the previous value with the new value. How can i do that? If there is any easier way to read the direction and speed please let me know. It is my first project with PLC and the program is writing to Ladder. I would deeply appreciated if anyone provides me an example or tip or any help. Thank you for your time. My best regards to all.
fla Posts: 3 Rating: (0)
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2/17/2011 3:17 PM	Rate (0)
Helmut_13 Posts: 2930 Rating: (432)	Hi, What you have is a AB Encoder. This is implemented in the HSC in AB mode. During comissioning you can go in the direction whar you expect to count up. If the HSC counts down, then change A/D wires. If this is all ok, then the PLC knows: Is A befor b then it turns right (form example) If B is for A then left. If two time the same signal comes, then you have a change in the direction. Can be detected with HSC. To meassure the time between pulses check if you can use the instruction BGN_ITIME and CAL_ITIME. This as I understand iswhat you want. Hope this helps
Helmut_13 Posts: 2930 Rating: (432)
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2/18/2011 9:04 AM	Rate (0)
Marcjan Diamond Member Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating: (716)	Found some interesting stuff here: /tf/WW/en/Posts/22906
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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2/18/2011 9:40 AM	Rate (0)
fla Posts: 3 Rating: (0)	hi to all, Thank you very much for your help. The instructions BGN_ITIME and CAL_ITIME is not working well to my project. I will now check the example that Marcjan suggests and i will inform the forum. Thank you all for your help My best regards.
fla Posts: 3 Rating: (0)
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2/21/2011 7:19 AM	Rate (0)
fla Posts: 3 Rating: (0)	hi to all, this is a good example that solve my problem: http://support.automation.siemens.com/WW/view/en/27864874 thank you very much my best regards to all
fla Posts: 3 Rating: (0)
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