Re: [CAD_CAM_EDM_DRO] Re: optical encoders

Hi George;

If that is indeed a stepper label, 200 pulses per rev may be indicating
that you have a 1.8 deg. stepper. If so this has nothing to do with
your encoder resolution. What it indicates is how far the stepper
turns upon each cycling of the motor.

One thing to consider is that a stepper is not really a motor. At
least they don't work in the same manner as a induction motor or DC
motor. Steppers are however very handy devices especially for cheap
digital control. Hooking them up to a very high resolution encoder
however is not a good idea. If you truely believe that you need the
resolution then consider a suitable servo technology.

Dave

george_barr wrote:

>Jon,
> I think the label on the motor says 200 Pulse Per Revolution and
>not Cycles Per Rev (CPR) of the encoder. I guess I have to see the
>specs on this motor to find out how man cycles/rev the motor itself
>can have. I am new to CNC and still need to learn things.
>
>Thanks,
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
>>george_barr wrote:
>>
>>
>>
>>>I have stepper motors with 200 pulses per revolution (ppr)
>>>
>>>
>encoders
>
>
>>>on them. I would like to upgrade the disc on the encoders to get
>>>higher resolutions on them. Does anyone know how high of
>>>
>>>
>resolution
>
>
>>>or PPR I can go? How much are the discs? Any advice?
>>>
>>>
>>>
>>>
>>What is the purpose of putting high resolution encoders on low
>>resolution motors?
>>Do you really think this will increase the resolution of the
>>
>>
>system?
>
>
>> Just because you
>>have X100 microstepping drives, do you think the motors can be
>>positioned in such
>>tiny fractions of a step? You can pretty much rely on getting half
>>steps, and probably
>>quarter steps, but friction interferes with getting much finer
>>
>>
>motion
>
>
>>than that.
>>I suspect you will end up with lots of hunting, but no real
>>
>>
>improvement in
>
>
>>actual positioning if you do this. If the current encoders are 200
>>cycle/rev, you
>>get 800 counts/rev if you count all transitions. I dislike
>>
>>
>pulses/rev
>
>
>>as it has an
>>imprecise meaning.
>>
>>Jon
>>
>>
>
>
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