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S7-1200 pulse generator with miliseconds base.

Created by: Sus_H at: 6/3/2015 6:27 PM (8 Replies)

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6/3/2015 6:27 PM	Rate (0)
Sus_H Posts: 4 Rating: (0)	Hi, currently i am working on small paint machine with s7-1200 onboard.The paint feeder is need to be used very fast. How can i do a pulse generator with miliseconds period base. For instance "ON" state will be for 40ms period and OFF will be for 65ms. My first mind was to use memory cpu clock and counter to count time. But the lowest period is 10Hz. So, the time-base will be only 100ms. Thanks in advance for ideas.
Sus_H Posts: 4 Rating: (0)
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6/3/2015 9:01 PM	Rate (0)
Joshua H. Advanced Member Joined: 5/6/2015 Last visit: 8/6/2025 Posts: 43 Rating: (7)	Hello, Have to looked in to the "CTRL_PWM (Pulse width modulation) instruction"? I would suggest searching for that instruction in the S7-1200 system manual. I have used the PWM instruction on the S7-200 and you can specify the PWM "Cycle Time" as well as the "Pulse On" in either milliseconds or microseconds. I would suspect that the S7-1200 would be fully capable of this function.

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6/4/2015 8:53 AM	Rate (0)
William_B Posts: 5225 Rating: (1204)	[delete answer that is not relating to question]
William_B Posts: 5225 Rating: (1204)	Last edited by: William_B at: 6/4/2015 12:01:48 PM delete answer
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6/4/2015 11:19 AM	Rate (0)
Sus_H Posts: 4 Rating: (0)	Thanks for all of the answers. Really, is that complicated to use 10ms time base? I don't want to control via frequency.The cycle of my machine is to: to turn on my paint machine (turning on means to digital output goes to on) for 40ms then off for 50ms (digital output back to off). After for instance 200 shots (i must count shots) i must disable the machine. I must read about PWM in S7-1200
Sus_H Posts: 4 Rating: (0)
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6/4/2015 11:36 AM	Rate (0)
William_B Posts: 5225 Rating: (1204)	Sus_H Thanks for all of the answers. Really, is that complicated to use 10ms time base? I don't want to control via frequency.The cycle of my machine is to: to turn on my paint machine (turning on means to digital output goes to on) for 40ms then off for 50ms (digital output back to off). After for instance 200 shots (i must count shots) i must disable the machine. I must read about PWM in S7-1200 I am sorry for not reading your question properly. There is simpler ways of doing this if the timing is not that critical then you can use normal IEC Timers. w
William_B Posts: 5225 Rating: (1204)	Last edited by: William_B at: 6/4/2015 11:39:01 AM
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6/4/2015 1:23 PM	Rate (0)
Sus_H Posts: 4 Rating: (0)	William_B don't worry. I'm new at siemens plc and i already just started learn how to read siemens documentations. I think "TP timer" is that what i am looking for. What is the time base for timers? Miliseconds?
Sus_H Posts: 4 Rating: (0)
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6/4/2015 2:34 PM	Rate (0)
Joshua H. Advanced Member Joined: 5/6/2015 Last visit: 8/6/2025 Posts: 43 Rating: (7)	I never used the IEC times but a quick read of the manual says the time base is in milliseconds. Play around with the TP Time and let us know if you have any issues or more questions.

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6/4/2015 4:30 PM	Rate (1)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/26/2025 Posts: 16149 Rating: (2516)	If you need more precise control, you might consider an OB that runs every 2 ms. Inside that OB, have it count. if it needs to count to 40, let it count 20 times. When it reaches 20, toggle the output. If it needs to count to 50, let it count 25 times. When it reaches 25, toggle the output, and count shot #. When shot # reaches 200, disable the output, and trigger the main OB to halt the machine via controlled shutdown (turning off air, turning on/off lights, etc.). Many ways to handle this. With the 2 ms OB, you need to have even number of ms in your timebase. If you set the OB to 1 ms, depending on your system and firmware level, it may not complete the 1 ms OB tasks fast enough and cause the plc to lock up and not perform the tasks properly. It is possible an OB with 1 ms cyclic time to work, but 2 ms is almost guaranteed to work. This avoids timers and running things using normal scan time which should achieve better repeatable results. If your 40/50 ms can vary a couple msec, timers will work fine and are easier to work with. Sus_H Thanks for all of the answers. Really, is that complicated to use 10ms time base? I don't want to control via frequency.The cycle of my machine is to: to turn on my paint machine (turning on means to digital output goes to on) for 40ms then off for 50ms (digital output back to off). After for instance 200 shots (i must count shots) i must disable the machine. I must read about PWM in S7-1200
	science guy
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This contribution was helpful to 1 thankful Users Joshua H.

5/18/2017 2:01 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4759 Rating: (122)	New question published by fiah is split to a separate thread with the subject Generate six pulse trains. Best regards Min_Moderator

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This contribution was helpful to 1 thankful Users mandrova

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