4/5/2009 5:35 AM | |
Posts: 8 Rating:
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Hi Tim, As I am beginner in LOGO!, would you please send a sample program about that ? I think it can useful for me. I remain, |
4/8/2009 7:55 AM | |
Joined: 3/21/2006 Last visit: 7/26/2024 Posts: 10228 Rating:
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Hello SRR, Have you seen Tips and Tricks LOGO! Hope this will helps. Best regards |
4/15/2009 9:29 PM | |
Posts: 8 Rating:
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OK, here's my simple example (as a zipped .lsc Logo file). It's for detecting thread breaks on sewing machines. During normal operation the sensor sends about 20 impulses/sec. The output is wired to the machine stop button. On a break, the impulses stop and (on this model) the input goes solid on. The PI ramp runs up and the comparator turns the output off, stopping the machine. The second input is "machine running", machine stopped resets the output and the PI, allowing the machine to be started again. For use with an encoder put an edge detecting gate on the input: on this particular machine the operator has a switch to overide detector operation by opening the sensor circuit, so I can't do that. This version is set up for a fixed timeout interval (long time so I can test it by hand in simulation): for variable speed you attach an analogue input to the PI setpoint, to vary the ramp rate (speed control), or to the comparator to vary the trip point (time control). Tim Attachmentus.ZIP (576 Downloads) |
4/16/2009 9:59 AM | |
Posts: 8 Rating:
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Hi Tim, Attachmentunderspeed.zip (536 Downloads) |
5/8/2009 11:14 PM | |
Posts: 8 Rating:
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I2 is the signal that tells the unit that the machine is running. If the unit trips, this signal going low means the machine has acknowledged its stop command, and so the trip can get reset. The delay prevents nuisance tripping while the machine is accelerating. Without this the unit would keep tripping w2hile the machine was stopped. The setpoint 0f 400 was just an arbitrary figure. It has to be some positive value if I do not use a speed control, as process variable is then always zero. The ramp rate obviously is proportional to the difference between the SP and the PV. The threshold of 465 on the comparator was how I tuned it to match the speed of the actual machine it was fastened to. It needs to be somewhere in the output range of the PI controller, you can use it as a range adjustment to set the maximum speed (full scale on your pot) to suit your machine, you could even use the "reference" button to connect it to an external adjusting pot. You can also set the range by changing the integrator time constant, but that only goes in steps of 1s. (you've set it to 1hr, that's awful slow, it should ideally be something like the time-out period (between encoder pulses) at full speed. It's neater to use PV rather than SP as your input, then the track shows on the drawing. If you connect your speed pot signal to the PV input, set the SP to zero and the direction to downwards; then the time to reach any specified level would be inversely proportional to the pot setting, so should track the inverter. Try this version in simulation. Set the two inputs to about 500, monitor the graph of the PI, and close I2. It's set up to need you to click I1 every few seconds to prevent tripping. Tim Attachmentus2.ZIP (587 Downloads) |
5/11/2009 10:29 PM | |
Joined: 1/5/2007 Last visit: 4/7/2023 Posts: 1690 Rating:
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Hi SRR, please, look at the attachment for my digital solution. The idea is a direct solution and measure the number of pulses per time, make a comparison with the given speed (as analoge input), and as option display the aktual measured speed in rpm. But to do that, it is impossible to use the block (digital) threshold trigger. An own circuit must programed...look my answers at "motor control" and at "Display of scaled High Speed Input Values" for more infos about this.... OK, the attachment contains a minimum version with circuit parameters witch are calculated in relation of your given values at your question. If you need more Infos to this program, then ask me here again.... Best regards Betel AttachmentDemo_Threshold_trigger_V3 (as under speed detector).zip (558 Downloads) |
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