RE: [CAD_CAM_EDM_DRO] Resolvers vs Encoders

The company I work for has used resolvers for years. The resolver output
isn't converted to digital, merely fed back to the servo preamplifier,
integrated with a PWM drive signal and tach signal from the motor, then
fed into the servo amplifier. So I suppose it's an open and closed loop.

Regards,
JJ

Be Kind, Be Careful, Be Yourself

> -----Original Message-----
> From: Peter Seddon [mailto:peter@...]
> Sent: Monday, October 21, 2002 4:41 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Resolvers vs Encoders
>
>
> We always used rotary brushless resolvers on machine tools which were
> originally developed for the military and hence fairly
> robust. They have one
> other advantage that they are absolute devices for one
> revolution. For most
> applications full travel of the machine will be a few tens of
> revolutions.
> We used the 2500Hz excitation frequency types and managed to
> get reasonably
> good performance and accuracy.
>
> The circuitry for using them is fairly simple using counters
> and comparators
> to energise and extract the position.
>
> Regards Peter
>
>
> ----- Original Message -----
> From: <w.higdon@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Sunday, October 20, 2002 10:39 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Resolvers vs Encoders
>
>
> > I'll try, altough Jon, could probaly do better.
> > A resolver can be a transformer with a 2 or more phase
> > primary. The secondary is inside the primary and is free
> > to move, some are linear, and some are rotary. The
> > Rotary ones usually use sliprings so the secondary can
> > rotate through a full circle (360). Being a analog
> > device the need something to convert them to digital.
> > The chips are rather expensive now, when I worked at
> > Entec, a new board cost between $500 to $1000 depending
> > on accuracy. a encoder can either be a "Absolute
> > encoder" (works just like a synchro with conversion
> > built in). These are usually VERY expensive and limited
> > in resloution. The second kind are "Incremental encoders"
> > these output a series of pulses as they are moved. If
> > they put out a pair of pulses streams with a phase
> > difference between the pulse streams can be used to
> > determine the direction of movement.
> > Now that this is as clear as mud, I'll let Jon or
> > someoone else clarify it.
> > Bill Higdon
> > PS you can convert a syncro machine to a eincremental
> > encoder machine, by replacing the syncro's with suitable
> > encoders. I did one upgrade (conversion)like that while
> > at Entec.
> > > Hi All:
> > > Can any of you explain to me, the differences between
> resolvers and
> > > encoders.
> > > What is the implication for machine performance?
> > > Is a retrofit from resolvers to encoders a worthwhile effort?
> > > When did resolvers go out of favour and why?
> > > I'm casting amorously about, for small CNC turning
> centers, and I've
> heard
> > > the terms mentioned, especially in regard to Hardinge machines.
> > > Mid eighties machines seem to be the transition point
> from the resolver
> > > system to the encoder system.
> > > It looks to me like there is a fair amount of very nice
> old CNC iron
> from
> > > that era out there available for very little
> money...certainly far less
> than
> > > building from scratch or retrofitting a manual
> machine...especially when
> you
> > > consider that the enclosures, the coolant pumps, the
> ballscrews, the way
> > > covers etc, etc are all already there.
> > > Cheers
> > >
> > > Marcus
> > >
> > >
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> > http://groups.yahoo.com/group/jobshophomeshop I consider this as a
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> are there, for OT
> subjects, that are not allowed on the CCED list.
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> Addresses:
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
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> to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>

http://groups.yahoo.com/group/jobshophomeshop I consider this as a
sister site to the CCED group, as many of the same members are there,
for OT subjects, that are not allowed on the CCED list.

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