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case-sensitive
November 6th, 2008, 03:36 AM
Hi there,

until now I only did ladder, but I have to program a speed ramp for a motor control using the analog output of a SIEMENS S7-200 PLC. How can I do that?

Regards,

Case.

BryanG
November 6th, 2008, 10:41 AM
Well, a ramp is just a value that gets bigger or smaller over time. So you could scale the current value of a timer or use a counter to count time pulses up or down. Or if it is just to ramp from one speed to another you could pass the value going to the analogue output through an averaging routine. Take your pick. Oh, and all this can easily be done using ladder logic.

Bryan

case-sensitive
November 6th, 2008, 05:22 PM
ok, will try. Example would g´have been nice.

Critt
November 6th, 2008, 08:49 PM
Hi Case-Sensitive, it may help if you show us what you have and then we can go from there. Many times there are students trying to get homework or project done here. Not saying this is the case but show us what you have and I'm sure we can take it from there.

case-sensitive
November 7th, 2008, 02:29 AM
something like that, just value is the analogue output, M0.2 triggers the timer again, than it adds the increment to the just value and so on. Just fiddling with start conditions and so on.

Was hoping there was some library thing so I don't have to do it from scratch.... Oh, its 2008...

case-sensitive
November 7th, 2008, 04:45 AM
nearly works, only not continuously, have the press the motor start button for it to count up again....

nonuke
November 7th, 2008, 10:43 AM
is this homework?
Why don't you just program the ramp in the VFD. You do have one??

case-sensitive
November 7th, 2008, 05:29 PM
more or less homework, industrial project, have to work it out myself, its to control a 90V DC motor with the Baldor KBMG-212D.

http://www.baldor.com.au/products/pdf/KBMG-212D%20info.pdf

As far as I understood the control needs an input voltage and controls the speed of the drive accordingly. So I would to program a ramp and different speeds/voltages to control the thing.
The project is to design a machine, including software, so we have to do it our selfs, school just provides computers and teacher is just there for OHS reasons. Its not to get the homework done for a PLC class.

nonuke
November 10th, 2008, 03:50 AM
Just implement the equation of a Straight Line: Y=mX+b
were x is the time, y is the analog output, m is the slope and b is the y intersept if you have one.

case-sensitive
November 10th, 2008, 03:21 PM
did these ones.
Just fiddling around with moving the values into the equations for forward/reverse, slow, fast, accelerate/decelerate....

case-sensitive
November 11th, 2008, 01:46 AM
there we go...

case-sensitive
January 14th, 2009, 01:45 AM
finally I got around to it:this is what I initially wanted to do, some sort of a blink thing. Guess its easier to adjust, timer value, set level and height between the steps. Cheers, Case.