Does anyone know of a cheap and accurate shaft encoder assembly,
suitable for that "professional rig feel" for spindle position to
frequency encoding. I'm thinking about some sort of integrated unit
that contains the encoder, code wheel, assembly, bearings etc.

Can anyone help....


Tim

In article .com,
wrote:

Does anyone know of a cheap and accurate shaft encoder assembly,
suitable for that "professional rig feel" for spindle position to
frequency encoding. I'm thinking about some sort of integrated unit
that contains the encoder, code wheel, assembly, bearings etc.

HP used to make very nice optical rotary encoders - e.g. the HEDS-7500
"digital potentiometer" (which has its own shaft and mounting), and
the HEDS-5000 series optical encoders (which mount on an existing
shaft). These are from a 1989 catalog, and the current versions or
equivalents are no doubt different. www.newark.com lists a bunch of
them.

I would not call them "cheap".

According to Digikey's catalog, Grayhill and Clarostat and Iwatsu and
Bourns all make similar rotary optical encoders with reasonably high
pulse-per-revolution counts (128 or 256).

It looks to me as if you're probably facing a price of $40 - $60 per
piece, in single quantities, for any commercially-made rotary encoder
of this caliber.

For anything very much less expensive, you'll probably have to
homebrew something (e.g. a couple of simple interruption-type
photosensors, and a code wheel laserprinted on a piece of plastic) and
mount it on an existing spindle/shaft.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:

In article .com,
wrote:



Does anyone know of a cheap and accurate shaft encoder assembly,
suitable for that "professional rig feel" for spindle position to
frequency encoding. I'm thinking about some sort of integrated unit
that contains the encoder, code wheel, assembly, bearings etc.



HP used to make very nice optical rotary encoders - e.g. the HEDS-7500
"digital potentiometer" (which has its own shaft and mounting), and
the HEDS-5000 series optical encoders (which mount on an existing
shaft). These are from a 1989 catalog, and the current versions or
equivalents are no doubt different. www.newark.com lists a bunch of
them.

I would not call them "cheap".

According to Digikey's catalog, Grayhill and Clarostat and Iwatsu and
Bourns all make similar rotary optical encoders with reasonably high
pulse-per-revolution counts (128 or 256).

It looks to me as if you're probably facing a price of $40 - $60 per
piece, in single quantities, for any commercially-made rotary encoder
of this caliber.

For anything very much less expensive, you'll probably have to
homebrew something (e.g. a couple of simple interruption-type
photosensors, and a code wheel laserprinted on a piece of plastic) and
mount it on an existing spindle/shaft.



Or take apart a computer mouse as they each have two.

Bill K7NOM

But nothing like 256 pulses/rev.

Cheers,
Tom

Tim:

There used to be a website with info on using surplus stepper motors as
precision shaft encoders. I have been doing Google searches without
success. Perhaps someone else will be able to provide a URL. It was
Australian, I believe.

Good luck.

Roger K6XQ

"Roger Leone" ) writes:
Tim:

There used to be a website with info on using surplus stepper motors as
precision shaft encoders. I have been doing Google searches without
success. Perhaps someone else will be able to provide a URL. It was
Australian, I believe.

Good luck.

Roger K6XQ



There was an article in "Radio Electronics" (or maybe it had morphed
into "Electronics Now" by that point), I'd say around 1994 or
so. The concept isn't much more than taking the outputs of the stepper
and putting them through comparators to get a binary waveform. But of course,
picking the right stepper is important since you need the fine steps, and I
know when I brought this up before, someone had something to say against
the concept, though I sure can't remember what they felt was wrong
with the concept.

Michael VE2BVW

Steppers have no output unless the shaft is moving. Steppers used this
way are really a velocity encoder and not a position encoder.


Regards,
Glenn AC7ZN

Steppers have no output unless the shaft is moving. Steppers used this
way are really a velocity encoder and not a position encoder.
Regards,
Glenn AC7ZN


Glenn:

I'm sure that limits stepper motors to certain uses, but I think this
thread/post may be incorrectly titled. Unless I misunderstand the intended
application, I don't think a "position encoder" is what he is looking for.
Rather he wants something that, when rotated, feeds pulses to an up/down
counter for frequency synthesis. The position of the shaft is not important
as long as its rotation can be used to generate pulses for the counter.

Roger

Roger Leone wrote:
Steppers have no output unless the shaft is moving. Steppers used this
way are really a velocity encoder and not a position encoder.
Regards,
Glenn AC7ZN


Glenn:

I'm sure that limits stepper motors to certain uses, but I think this
thread/post may be incorrectly titled. Unless I misunderstand the intended
application, I don't think a "position encoder" is what he is looking for.
Rather he wants something that, when rotated, feeds pulses to an up/down
counter for frequency synthesis. The position of the shaft is not important
as long as its rotation can be used to generate pulses for the counter.

Roger

Roger:

Yes you're right, that's exactly what I'm looking for... any ideas as
to where I might get such a beast?

Tim

In article om,

I'm sure that limits stepper motors to certain uses, but I think this
thread/post may be incorrectly titled. Unless I misunderstand the intended
application, I don't think a "position encoder" is what he is looking for.
Rather he wants something that, when rotated, feeds pulses to an up/down
counter for frequency synthesis. The position of the shaft is not important
as long as its rotation can be used to generate pulses for the counter.

Roger

Roger:

Yes you're right, that's exactly what I'm looking for... any ideas as
to where I might get such a beast?

Usually known as a "rotary encoder". They normally have two outputs,
in a phase-quadrature arrangment. These can be decoded to create
up/down/clock pulses using dedicated ICs (HP makes 'em), or via a small
collection of discrete TTL logic chips, or via a simple software
routine in a PIC micro or similar (which is how I'd probably do it
these days... I wrote a simple state-table routine for an 8051 some
years back which worked out quite well).

You'll probably want at least 64 counts per revolution, and probably
256, to get a nice smooth "feel" to the synthesizer tuning. Most such
use an optical code wheel and a pair of optosensors.

Digi-Key catalog lists quite a few such (all with their own shafts,
ready for panel mounting), but they aren't cheap. Mechanical rotary
encoders are less expensive, but less precise (fewer counts per
revolution) and possibly not as reliable or long-lived since they use
mechanical contacts.


--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!