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Question about stepper motor

Question about stepper motor

Question about stepper motor

(OP)
I am new to using stepper motors and have been asked to implement one at my plant for a relatively simple task at my plant.  My plant already had the Motor(Slo-Syn KMT093F) and Drive(Industrial Devices "NextStep"), and the drive has a Step/CW and Dir/CCW inputs.  

My question is, do I need an indexer?  Can you just control this with a potentiometer?

Any info here or where I can find an informative guide on the internet would be appreciated.  Googled it but didn't get the simpler info I'm looking for.

RE: Question about stepper motor

(OP)
ok... I had already read the manual.  I was trying to say I don't get it.  The drive(and in the manual) clearly states on the input side "to indexer"... what is a stepper motor indexer?  What does it do(square wave generator?)?  Can you buy one?

I have looked up general stepper motor information and read this manual, all the information I've looked up shows:

indexer >>> drive >>> motor

yet I am having a hard time locating an actual "indexer", or is this a function normally handled from a PLC, PC, or microprocessor and not an actual device(in and of itself)?  I am looking for simplistic information on commercially available stepper motors and controls.  All the info I can find on the internet seems to be of the hobbiest type where people are controlling old floppy drives from their computers printer port.  That information is not helpful to me.  

RE: Question about stepper motor

For the drive, the step and direction inputs are usually used as

Direction= CW or CCW

Step=The motor makes one step for every pulse input (how much a step is is controlled inside the drive).

To create the DIR and Step pulses, an indexer is usually used.  The indexer is some kind of digital controller that outputs step and direction commands usually to move from one position to another.

One way of doing this is through an add on module to a PLC.  Probabvly the most common module is one that simply get position commands from the PLC and the module takes care of direction, number of steps, acceleration ramping, maximum pulse rate, etc.

RE: Question about stepper motor

Yes, an indexer is a square wave generator, with a few extra capabilities.  It emits a square wave for a programmed number of pulses.  It has the capability of starting the pulses at a low frequency, ramping the frequency up, slewing the motor at constant speed, and ramping the frequency (and the motor speed) down again, and stopping at a predermined point, or when a position switch is triggered, or ... there are a lot of behaviors available.

The ramping is necessary because step motors can move loads that they can't start at a given speed, by starting at a lower speed, etc.  Their dynamics are pretty complex.

It's possible to drive a stepper at constant speed for a counted number of steps from a PC printer port with very little code.  Ramping and position seeking can be tricky, so in an industrial setting, as you suspect, it makes sense to spend money on fancier hardware that takes care of most of the aggravating details, and unlike homebrew code, has well documented behaviors.

Mike Halloran
Pembroke Pines, FL, USA

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