Re: [CAD_CAM_EDM_DRO] Re: rotary hand encoder wheels with detent

Hi Alan,

I did make the suggestion of using a mouse partly tongue in cheek as there
have been so many discussions of their use as encoders. However, I have
taken this a little further and done a dental check up on a couple of mice
which has revealed that, as with anything in nature, everything has
variations and, of three mice I inspected, two had 36 teeth, one 24 teeth
and one 30 teeth so it may be that somewhere out there, there is a mouse
with a useful number of teeth!
Having said that, why do we need 100 clicks per rev of the handwheel? I
thought the whole idea was that, rather than working to any precise portion
of a revolution, you actually counted the clicks by touch. This being the
case, it wouldn't really matter how many 'teeth' are on the wheel as long as
you could depend on one click moving the machine table one increment - so,
give the handwheel 72 detent positions and you have a nice ratio between the
wheel and the mouse encoder disk. (and, of course, 72 would be a nice
relevant number for a rotary table..)
In actual practice I suspect that the number of teeth on the encoder disk
will not matter a lot and that all you need is a precise ratio drive from
the handwheel to the encoder disk which can be achieved by carefully turned
shafts and decent rubber band drives (like in good tape recorders), then, so
long as the encoder spins so as to produce a number of pulses for each
detent click, you can divide these down in electronics to give one pulse per
position and even out any errors in the encoder teeth (not that this is
particularly relevant in this application either!)
The point really is that this would give a more positive pulse than a
stepper motor, would have a more positive 'click' (spring working on the
teeth of an old clock wheel or other gear fixed to the handwheel) and the
hardware would be cheap and easily fabricated by anyone with even
rudimentary equipment. The electronics to interface it with EMC may be more
problematic but I'm sure there are people on this list who would scoff at
the challenge//;O)

Best wishes,
Ian
--

Ian W. Wright
Sheffield, UK

----- Original Message -----
From: <flyspeck1@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, February 15, 2002 12:07 AM
Subject: [CAD_CAM_EDM_DRO] Re: rotary hand encoder wheels with detent


>
> It doesn't
>
> I am not too certain that using a mouse would work very
> well. I just counted the number of serrations that you
> get on a mouse and it is 36; based on previous
> conversations on this group, that cannot be increased.
> What we really want, however, is a something that
> divides 100 cleanly..... If we were to use a 1.8 degree
>
> Or.... I am missing something! Sure, I guess you could
> multiply it up pretty far, but it still seems like a
> less than ideal setup. Too bad... I liked the idea too.
>
> --Alan
>
> <<<<Original Post>>>>
> Message: 11
> Date: Thu, 14 Feb 2002 19:28:02 -0000
> From: "Ian W. Wright" <Ian@...>
> Subject: Re: Re: rotary hand encoder wheels with detent
>
> Perhaps, at last, this is a use for the encoder wheel
> out of a mouse!!! ;o)
> Hand wheel with clicks, and a rubber band drive from the
> hand wheel shaft to
> the encoder spindle to gear it up in a suitable
> ratio.....
>
> Best wishes,
> Ian
> --
>
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