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S7-300 software solution

Created by: nalbert at: 4/12/2006 2:07 PM (3 Replies)

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4/12/2006 2:07 PM	Rate (0)
nalbert Posts: 2 Rating: (0)	Hello everybody. My task is to control a Danfoss frequency converter with pulse ( 10Hz - 80 Hz ). For this I have a 314 IFM PLC and I have to do it with an ordinary output (Q 125.5 ). I use the FB 43 "PULSEGEN" function block, but this solution has 2 - 3 Hz fluctuation. Is there any other solution, or I have to check the Danfoss wether it has a parameter to smooth the control signal? Thanks in advance. Albert
nalbert Posts: 2 Rating: (0)
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4/13/2006 12:54 PM	Rate (0)
usjwo Posts: 36 Rating: (9)	I don’t know FB43. But please try to use “Clock Memory Byte” (HW config/CPU Properties/Cycle/Clock Memory) and OB35 (cyclic interrupts).
usjwo Posts: 36 Rating: (9)
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4/15/2006 9:03 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Hi nalbert, You may use OB35 to do this, if OB35 is placed on a shorter time then it is possible to make pulses that are 2 times the OB35 time. You have to set the outputs directly in the perifery, for Q-byte 125 this will be T PQB 125. Don't forget to set also the output byte in the PIQ, with setting the bit or byte T QB 125.
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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4/20/2006 10:51 AM	Rate (0)
nalbert Posts: 2 Rating: (0)	Thank you for the quick response. My first thought was also the OB35, but it doesn't work accurately. I could make only 20 Hz precisely. In higher frequency range the OB35fluctuated a lot between 40 and 60 Hz. As the program execusion time grows, the OB35 came continually inaccurate. The OB35 has very low priority. So I tried it, but I couldn't do it, maybe I did something wrong. If you had a concrete solution, I would take it with pleasure. Albert
nalbert Posts: 2 Rating: (0)
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