Re: rotary hand encoder
Posted by
flyspeck1@a...
on 2002-02-15 13:38:56 UTC
Hi Ian:
That is good to know about the mice. I didn't mean to
take it as gospel that they were all 36 count wheels. I
don't doubt that there are probably a myriad of
different ones out there.
The point I had been trying to make about the 100 clicks
per revolution really was a result of something Fred (I
think it was him) mentioned on the subject of jog
wheels. He indicated, and I agree, that it is extremely
useful having a full revolution be a set amount. Now, I
am biased because I'm in the states... but, 100 thou
seems like a very good number to use in that scenario.
Seeing as there is/was a desire to use a 200 step motor
for the "click" generator, that works out great.
Each "click" would translate to a half thou. The only
problem remains in ensuring that the computer gets the
same number of pulses (or multiple thereof). Because 36
doesn't work in very well into the equation, that is
where the comment came from.
Actually, all of this has gotten me thinking that it
would be a fun project to build up a nice pulse
generator. I'm thinking about using either a stepper or
a round that has 200 flats milled on it (plus a bar
laying over it to give the detent feel). I'm then
thinking of building a very crude encoder. It doesn't
need to be that fancy so long as it can give me
direction and 200 cycles per revolution (i.e. the
individual transitions don't have to be "centered" in
the pulse line accurately because that isn't the goal
here.
I've got a preliminary design I'm thinking about. If
anyone else is interested in this I can probably draw it
up and publish it to the dropbox. Otherwise I'll wait
and send in the info when I'm done (or I abandon the
project). Of course I'm going snow, errrr water, skiing
this weekend; one has to have priorities!
Anyhow, that is about it. This thread seems to be about
dead so maybe you, Ian, and I are the only two people
who are interested in it now. Whatever the case, thank
you for you input.
--Alan
<<< original post >>>>
Subject: Re: 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
That is good to know about the mice. I didn't mean to
take it as gospel that they were all 36 count wheels. I
don't doubt that there are probably a myriad of
different ones out there.
The point I had been trying to make about the 100 clicks
per revolution really was a result of something Fred (I
think it was him) mentioned on the subject of jog
wheels. He indicated, and I agree, that it is extremely
useful having a full revolution be a set amount. Now, I
am biased because I'm in the states... but, 100 thou
seems like a very good number to use in that scenario.
Seeing as there is/was a desire to use a 200 step motor
for the "click" generator, that works out great.
Each "click" would translate to a half thou. The only
problem remains in ensuring that the computer gets the
same number of pulses (or multiple thereof). Because 36
doesn't work in very well into the equation, that is
where the comment came from.
Actually, all of this has gotten me thinking that it
would be a fun project to build up a nice pulse
generator. I'm thinking about using either a stepper or
a round that has 200 flats milled on it (plus a bar
laying over it to give the detent feel). I'm then
thinking of building a very crude encoder. It doesn't
need to be that fancy so long as it can give me
direction and 200 cycles per revolution (i.e. the
individual transitions don't have to be "centered" in
the pulse line accurately because that isn't the goal
here.
I've got a preliminary design I'm thinking about. If
anyone else is interested in this I can probably draw it
up and publish it to the dropbox. Otherwise I'll wait
and send in the info when I'm done (or I abandon the
project). Of course I'm going snow, errrr water, skiing
this weekend; one has to have priorities!
Anyhow, that is about it. This thread seems to be about
dead so maybe you, Ian, and I are the only two people
who are interested in it now. Whatever the case, thank
you for you input.
--Alan
<<< original post >>>>
Subject: Re: 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