wrote:

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


For something inexpensive, consider the encoder in a wheel mouse. Also
most ball mice include two encoders for the ball.

craigm

On Thu, 14 Jul 2005 01:00:45 +0000, Roger Leone wrote:

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

That was probably on Richard Hosking's (VK6BRO) web-page.
The page seems to have disappeared from the web. Hopefully
it has moved to a new URL. Are you lurking here Richard?

This page has some info:
http://www.webx.dk/oz2cpu/20m/encoder.htm

73, Ed. EI9GQ.



--
Linux 2.6.12.1
Remove 'X' to reply by e-mail.

"Dave Platt" wrote in message
...
In article om,

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.

Depending on the application, mechanical encoders are pretty good, and
getting better. As a tuning control, in most cases something on the order
of 50 pulses per rev is pretty useable and avaliable in a mechanical
encoder. Much more than that and you are getting into the optical encoders
which do get kind of pricey. They -feel- really nice, though.

Most of the mechanical encoders Digikey carries are detented, so watch out
for that. The few that aren't are pretty decent. Mechanical encoders are
typically under $5, while the opticals are more like $50. But the nice
ball-bearing feel might be worth it, depending on your project.

...

Dave Platt wrote:

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.

For something like a receiver tuning control, even 256 steps/rev would
sound 'jumpy'. However, you could gear it up mechanically so that even a
small movement of the control produces several pulses from the encoder.
That is exactly what happens in a mouse.

Try an old-fashioned cord drive, only in reverse.


--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Ian White G/GM3SEK" wrote in message
...

For something like a receiver tuning control, even 256 steps/rev would
sound 'jumpy'. However, you could gear it up mechanically so that even a

Actually, 256 is getting too high in most cases. The "jumpiness" comes from
the size of the step, i.e., the number of Hz per step. Encoders between 50
and 100 are probably the easiest to deal with. You generally want to make
the step size small, like 1 or 10 Hz, but you don't want hundreds of turns
to cover the band. At very high resolutions, the pulses can come very fast,
so it gets tricky to distinguish the closure from noise. Of course,
higher counts can be made to work, and in principle, can be made to work
better. But generally, one is dealing with low level software and finite
compute resources to read the encoder, so the very high resolutions can
actually become somewhat problematic.

...

From: xpyttl on Jul 17, 5:56 pm

"Ian White G/GM3SEK" wrote in message
...

For something like a receiver tuning control, even 256 steps/rev would
sound 'jumpy'. However, you could gear it up mechanically so that even a

Actually, 256 is getting too high in most cases. The "jumpiness" comes from
the size of the step, i.e., the number of Hz per step. Encoders between 50
and 100 are probably the easiest to deal with. You generally want to make
the step size small, like 1 or 10 Hz, but you don't want hundreds of turns
to cover the band.

Ahem, have you guys agreed on what defines "jumpiness?" :-)

I'm into the actual receiver portion of a PLL-LO-controlled
HF SW BC receiver tuning in 1 KHz steps. The PLL and its
controlling circuitry are done and a 256-step Grayhill shaft
encoder is used with a shaft encoder decoder circuit from Dr.
Robert Dennis. That decoder circuit uses 3 HCMOS DIPs for
Up/Down counters having separate Up and Down clocks. One more
HCMOS DIP gate package is required for Up/Down counters having
a single clock input and having an Up or Down mode control pin.

At very high resolutions, the pulses can come very fast,
so it gets tricky to distinguish the closure from noise.

I didn't find it so. The Dennis Decoder will allow shaft
encoder rotation rates of 150 RPM with a 240-step shaft
encoder, no problem. Pressed faster, it can handle 300 RPM
or 5 revolutions per second...quite fast tuning. It is
easily comparable to the "old" tuning control on my Icom
IC-R70 which has an estimated 200 steps per revolution.

Of course,
higher counts can be made to work, and in principle, can be made to work
better. But generally, one is dealing with low level software and finite
compute resources to read the encoder, so the very high resolutions can
actually become somewhat problematic.

While the BCD Up/Down counter ICs are getting rather scarce,
it takes only three more packages to "see" three-decimal-digit
resolution. Add another IC for four-decimal-digit resolution.
4-stage binary Up/Down counters are still being made, no problem.

Ain't no software for this critter...it's all hardware. The
Up/Down counter drives the PLL divider directly (through a
EPROM translator, preprogrammed, or through some more logic
gates). Grayhill shaft encoder output is TTL/HCMOS level at
+5 VDC into the encoder. Very fast jumps in handling the
shaft encoder knob don't upset the counter chain.

If you want some nice decoder circuit schematics and a set of
decoder waveforms, let me know at signature address below and
I can attach the ZIP file (19 K) to e-mail.

If someone wants an Absolute position control, that could be
done with an additional optical sensor and track that resets
the Up/Down counter at all-zeroes. Not the same as a Gray
Code multiple track and sensor encoder with a collection of
Exclusive-Or gates to make it straight binary, but cheaper.

bit bit

Seems to me that 256 or 512 is reasonable. Then decide how many
kHz/rev you want, and that tells you the step size. If you want
10kHz/rev, 512 steps would give you just under 20Hz/step, which seems
reasonable to me. I wouldn't want it any coarser than that, and I'd
actually prefer finer. Processors are very cheap; you can easily
process the quadrature step info up to dozens of revolutions per
second. If you budget ten instruction cycles to process each step, and
you're using a slow processor at 1usec/instruction cycle, you can
process 100,000 steps a second, if the processor has nothing else to
do. You can process 10,000 steps a second, or 200kHz/second, with just
ten percent of the processor's time. A nice "plus" is to accelerate
the tuning when the steps come fast, so you might bump the tuning up to
higher Hz/step as the steps come faster. Expect to spend some time on
the algorithm to get a smooth "feel" to it, though. The accelerated
tuning when the knob is turned more quickly is a feature commonly found
in test instruments. I haven't ever had a problem with the HP/Agilent
encoders with respect to the output looking like "noise." The outputs
are very clean digital signals with no "bounce" if you're turning in
one direction.

Cheers,
Tom

PS...Tim, did you find an encoder yet? Drop me an email if not...

One you can find at http://ru3ga.qrz.ru/UZLY/encod.htm

Follow the links on that page for more pictures.

Sorry, the text is not in English. If anybody wants more details, let me
know.
73,
Ivan
VE3IVM


"Roger Leone" wrote in message
...
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

From: xpyttl on Jul 17, 5:56 pm
"Ian White G/GM3SEK" wrote in message
...

For something like a receiver tuning control, even 256 steps/rev would
sound 'jumpy'. However, you could gear it up mechanically so that even a

Actually, 256 is getting too high in most cases. The "jumpiness" comes from
the size of the step, i.e., the number of Hz per step. Encoders between 50
and 100 are probably the easiest to deal with. You generally want to make
the step size small, like 1 or 10 Hz, but you don't want hundreds of turns
to cover the band.

I'm into the actual receiver portion of a PLL-LO-controlled
HF SW BC receiver tuning in 1 KHz steps. The PLL and its
controlling circuitry are done and a 256-step Grayhill shaft
encoder is used with a shaft encoder decoder circuit from Dr.
Robert Dennis. That decoder circuit uses 3 HCMOS DIPs for
Up/Down counters having separate Up and Down clocks. One more
HCMOS DIP gate package is required for Up/Down counters having
a single clock input and having an Up or Down mode control pin.

At very high resolutions, the pulses can come very fast,
so it gets tricky to distinguish the closure from noise.

I didn't find it so. The Dennis Decoder will allow shaft
encoder rotation rates of 150 RPM with a 240-step shaft
encoder, no problem. Pressed faster, it can handle 300 RPM
or 5 revolutions per second...quite fast tuning. It is

ADDENDA:

The decoder circuit I used was from:

http://www-personal.umich.edu/~bobde...re_decoder.pdf

Two internal time-constants were about 10 times faster than
what I'm using for the tuning control on my receiver project.
I deliberately lengthened the two internal pulses used in
decoding to better observe them on a scope.

The Dennis Decoder is indicated as originating in 1998.

[University of Michigan, not Michigan State University. :-) ]

wrote:
From: xpyttl on Jul 17, 5:56 pm
"Ian White G/GM3SEK" wrote in message
...

For something like a receiver tuning control, even 256 steps/rev would
sound 'jumpy'. However, you could gear it up mechanically so that even a

Actually, 256 is getting too high in most cases. The "jumpiness" comes from
the size of the step, i.e., the number of Hz per step. Encoders between 50
and 100 are probably the easiest to deal with. You generally want to make
the step size small, like 1 or 10 Hz, but you don't want hundreds of turns
to cover the band.

I'm into the actual receiver portion of a PLL-LO-controlled
HF SW BC receiver tuning in 1 KHz steps. The PLL and its
controlling circuitry are done and a 256-step Grayhill shaft
encoder is used with a shaft encoder decoder circuit from Dr.
Robert Dennis. That decoder circuit uses 3 HCMOS DIPs for
Up/Down counters having separate Up and Down clocks. One more
HCMOS DIP gate package is required for Up/Down counters having
a single clock input and having an Up or Down mode control pin.

At very high resolutions, the pulses can come very fast,
so it gets tricky to distinguish the closure from noise.

I didn't find it so. The Dennis Decoder will allow shaft
encoder rotation rates of 150 RPM with a 240-step shaft
encoder, no problem. Pressed faster, it can handle 300 RPM
or 5 revolutions per second...quite fast tuning. It is

ADDENDA:

The decoder circuit I used was from:

http://www-personal.umich.edu/~bobde...re_decoder.pdf

Two internal time-constants were about 10 times faster than
what I'm using for the tuning control on my receiver project.
I deliberately lengthened the two internal pulses used in
decoding to better observe them on a scope.

The Dennis Decoder is indicated as originating in 1998.

[University of Michigan, not Michigan State University. :-) ]




Actually, if you want to be disgustingly cheap and easy (no machining
required) then use a wheel mouse (complete) - plug it into your radio,
and decode the wheel pulses for up/down = simple switch select and a
few gates for tuning "rate". Worth a try - its not the space shuttle
your trying to build.

73 de VK3BFA Andrew