This is all regarding this old Troyke CNC rotary table that I wanted
If you recall, the latest stumbling block with the rotary table was
that it was using a old technology "resolver" for position feedback.

I was able to get a hold of Joe at Harowe, who made this
resolver. Apparently, this resolver is still in surrent production and
sells for a modest sum of $1,423.00.

http://www.dynapar.com/Accessories.a...BRW-300-F10/10

Joe emailed me a diagram of this motor with all electrical
information.

http://igor.chudov.com/manuals/Harow...300-F10-10.pdf

This looks like super duper space age technology from very many years
ago and is, apparently, a high quality product that is likely in good
shape.

So, at this point, I have two routes to take:

1) Attach a shaft extension in the back and a new encoder from US
Digital
or
2) Add a resolver to encoder converter.

Both have the same cost, these ir some machining involved in both
cases. In the first I have to add a shaft extension, in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.

After some thinking and talking to EMC guys on IRC, I will go with the
resolver. It is, in a certain way, a better device (though far more
expensive!)

This is so because if the encoder misses a pulse due to noise, it
eventually recovers the absolute position. Plus they are more
"crap-proof".

i

On Aug 3, 3:35*pm, Ignoramus30076 ignoramus30...@NOSPAM.
30076.invalid wrote:
This is all regarding this old Troyke CNC rotary table that I wanted
If you recall, the latest stumbling block with the rotary table was
that it was using a old technology "resolver" for position feedback.

I was able to get a hold of Joe at Harowe, who made this
resolver. Apparently, this resolver is still in surrent production and
sells for a modest sum of $1,423.00.

* * *http://www.dynapar.com/Accessories.a...BRW-300-F10/10

Joe emailed me a diagram of this motor with all electrical
information.

http://igor.chudov.com/manuals/Harow...300-F10-10.pdf

This looks like super duper space age technology from very many years
ago and is, apparently, a high quality product that is likely in good
shape.

So, at this point, I have two routes to take:

1) Attach a shaft extension in the back and a new encoder from US
Digital
or
2) Add a resolver to encoder converter.

Both have the same cost, these ir some machining involved in both
cases. In the first I have to add a shaft extension, in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.

After some thinking and talking to EMC guys on IRC, I will go with the
resolver. It is, in a certain way, a better device (though far more
expensive!)

This is so because if the encoder misses a pulse due to noise, it
eventually recovers the absolute position. Plus they are more
"crap-proof".

i

Iggy,

With your background you can appreciate the electronics of the
conversion.
Some texts will tell you that the rotor is energized with a sine wave,
and the Sine Cosine outputs are quadrature decoded to find the current
position of the rotor. This sounds straightforward, but in fact by
definition the Sine and Cosine levels will rise and fall to zero as
the rotor revolves. This makes the detection circuitry susceptible to
noise.
The difference between the Sine and Cosine signals indicate the rotary
position.
Another method to read a resolver position, which I found to be
technically superior, was to drive the Sine Cosine coils with
digitally synthesized Sine Cosine signals. The rotor coil then became
the sensing element.

As the rotor rotates, the signal from the rotor coil will be a fairly
constant amplitude, but will vary in phase relationships to the Sine/
Cosine drive signals.

To summarize the circuit, there is a master counter that counts up to
the maximum resolution of the resolver, and resets. The output of that
drives the Sine and Cosine lookup ROMs which drive the D/A and drive
the Sine/Cosine Drivers to the resolver.
The rotor signal is simply fed to a Zero Crossing detector. When it
detects a Zero crossing, the current value of the free running counter
is captured, and that is the current position of the resolver.
So, it acts as an absolute encoder.
The signals from the resolver are always at full amplitude, and only
timing of the zero crossing point determines the absolute position.

I thought you would fine that interesting, from a design point of view.

Ignoramus30076 wrote:

This is all regarding this old Troyke CNC rotary table that I wanted
If you recall, the latest stumbling block with the rotary table was
that it was using a old technology "resolver" for position feedback.

I was able to get a hold of Joe at Harowe, who made this
resolver. Apparently, this resolver is still in surrent production and
sells for a modest sum of $1,423.00.

http://www.dynapar.com/Accessories.a...BRW-300-F10/10

Joe emailed me a diagram of this motor with all electrical
information.

http://igor.chudov.com/manuals/Harow...300-F10-10.pdf

This looks like super duper space age technology from very many years
ago and is, apparently, a high quality product that is likely in good
shape.

So, at this point, I have two routes to take:

1) Attach a shaft extension in the back and a new encoder from US
Digital
or
2) Add a resolver to encoder converter.

Both have the same cost, these ir some machining involved in both
cases. In the first I have to add a shaft extension, in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.

After some thinking and talking to EMC guys on IRC, I will go with the
resolver. It is, in a certain way, a better device (though far more
expensive!)

This is so because if the encoder misses a pulse due to noise, it
eventually recovers the absolute position. Plus they are more
"crap-proof".

i

The idea that after missing some pulses the resolver will recover
absolute position eventually is pretty useless in this application,
since you have something like a 90:1 drive ratio to the table, and
knowing the motor is at position X tells you nothing about the position
of the RT. If you loose pulses your RT will remain off until you re-home
it. You should also not have any noise issues if you use shielded
cables, and ideally differential line drivers and receivers.

On Aug 3, 4:56*pm, Cross-Slide wrote:
On Aug 3, 3:35*pm, Ignoramus30076 ignoramus30...@NOSPAM.
...
Another method to read a resolver position, which I found to be
technically superior, was to drive the Sine Cosine coils with
digitally synthesized Sine Cosine signals. The rotor coil then became
the sensing element.
...

http://www.analog.com/library/analog...38-08/dds.html

Decoding the I and Q (Sine and Cosine) signals in digital radios was
done in software and I have no experience with it.

jsw

On Tue, 03 Aug 2010 15:35:15 -0500, Ignoramus30076
wrote:

in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.


#1 consideration.. the converter can go inside the old control cabinet.

#2 consideration...never never never put a plug/connector at the rotary
table. Run good quality shielded cable in a length long enough to plug
into the control cabinet on the side or bottom away from the machining
area and all chips and splash.

Gunner


"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

On 2010-08-04, Gunner Asch wrote:
On Tue, 03 Aug 2010 15:35:15 -0500, Ignoramus30076
wrote:

in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.


#1 consideration.. the converter can go inside the old control cabinet.

#2 consideration...never never never put a plug/connector at the rotary
table. Run good quality shielded cable in a length long enough to plug
into the control cabinet on the side or bottom away from the machining
area and all chips and splash.

Yes, I am convinced.

i

That is exactly the design used for aircraft magnetic compass repeaters. Typically they use a 400 to 600 Hz oscillator as a
reference.
Steve

"Cross-Slide" wrote in message ...
On Aug 3, 3:35 pm, Ignoramus30076 ignoramus30...@NOSPAM.
30076.invalid wrote:
This is all regarding this old Troyke CNC rotary table that I wanted
If you recall, the latest stumbling block with the rotary table was
that it was using a old technology "resolver" for position feedback.

I was able to get a hold of Joe at Harowe, who made this
resolver. Apparently, this resolver is still in surrent production and
sells for a modest sum of $1,423.00.

http://www.dynapar.com/Accessories.a...BRW-300-F10/10

Joe emailed me a diagram of this motor with all electrical
information.

http://igor.chudov.com/manuals/Harow...300-F10-10.pdf

This looks like super duper space age technology from very many years
ago and is, apparently, a high quality product that is likely in good
shape.

So, at this point, I have two routes to take:

1) Attach a shaft extension in the back and a new encoder from US
Digital
or
2) Add a resolver to encoder converter.

Both have the same cost, these ir some machining involved in both
cases. In the first I have to add a shaft extension, in the second I
have to add an enclosure for the converter and a plug/receptacle to
the rotary table. This is so, because I may need to unplug the rotary
table and remove it from the mill from time to time.

After some thinking and talking to EMC guys on IRC, I will go with the
resolver. It is, in a certain way, a better device (though far more
expensive!)

This is so because if the encoder misses a pulse due to noise, it
eventually recovers the absolute position. Plus they are more
"crap-proof".

i

Iggy,

With your background you can appreciate the electronics of the
conversion.
Some texts will tell you that the rotor is energized with a sine wave,
and the Sine Cosine outputs are quadrature decoded to find the current
position of the rotor. This sounds straightforward, but in fact by
definition the Sine and Cosine levels will rise and fall to zero as
the rotor revolves. This makes the detection circuitry susceptible to
noise.
The difference between the Sine and Cosine signals indicate the rotary
position.
Another method to read a resolver position, which I found to be
technically superior, was to drive the Sine Cosine coils with
digitally synthesized Sine Cosine signals. The rotor coil then became
the sensing element.

As the rotor rotates, the signal from the rotor coil will be a fairly
constant amplitude, but will vary in phase relationships to the Sine/
Cosine drive signals.

To summarize the circuit, there is a master counter that counts up to
the maximum resolution of the resolver, and resets. The output of that
drives the Sine and Cosine lookup ROMs which drive the D/A and drive
the Sine/Cosine Drivers to the resolver.
The rotor signal is simply fed to a Zero Crossing detector. When it
detects a Zero crossing, the current value of the free running counter
is captured, and that is the current position of the resolver.
So, it acts as an absolute encoder.
The signals from the resolver are always at full amplitude, and only
timing of the zero crossing point determines the absolute position.

I thought you would fine that interesting, from a design point of view.

Steve Lusardi wrote:

That is exactly the design used for aircraft magnetic compass repeaters. Typically they use a 400 to 600 Hz oscillator as a
reference.
Steve

Yes, however it is of little benefit on the RT, with the resolver on the
servo shaft, where a given servo shaft position equates to some 90
possible RT positions. If the resolver were connected directly to the RT
it might provide some benefit over and encoder, but not when mounted to
the servo. In this case I'd recommend Iggy just replace the resolver
with another encoder, and sell the resolver to someone who needs it for
a tidy profit.

"Pete C." fired this volley in news:4c596f58$0
:

Yes, however it is of little benefit on the RT, with the resolver on
the
servo shaft, where a given servo shaft position equates to some 90
possible RT positions. If the resolver were connected directly to the
RT
it might provide some benefit over and encoder, but not when mounted to
the servo. In this case I'd recommend Iggy just replace the resolver
with another encoder, and sell the resolver to someone who needs it for
a tidy profit.


I wonder if that might be a way to "remote" an encoder. Make the
resolver into half a SlowSyn pair, and mount the encoder on the other
one. ???

I still have reservations about the difficulty of extending that motor's
shaft.

One thought came to mind, Ig:

I know there's a scant 1/8" of shaft "showing" past the bearing, but
given the almost vanishingly small load that extension will be under, and
given the quality of modern metalworking adhesives, I wonder if you could
just make a short hub that fit snugly over the stub of shaft with the
bottom of the hole in the hub milled flat to aid in alignment, and was
secured with a permanent anaerobic adhesive.

LLoyd

"Lloyd E. Sponenburgh" wrote:

"Pete C." fired this volley in news:4c596f58$0
:

Yes, however it is of little benefit on the RT, with the resolver on
the
servo shaft, where a given servo shaft position equates to some 90
possible RT positions. If the resolver were connected directly to the
RT
it might provide some benefit over and encoder, but not when mounted to
the servo. In this case I'd recommend Iggy just replace the resolver
with another encoder, and sell the resolver to someone who needs it for
a tidy profit.


I wonder if that might be a way to "remote" an encoder. Make the
resolver into half a SlowSyn pair, and mount the encoder on the other
one. ???

I still have reservations about the difficulty of extending that motor's
shaft.

One thought came to mind, Ig:

I know there's a scant 1/8" of shaft "showing" past the bearing, but
given the almost vanishingly small load that extension will be under, and
given the quality of modern metalworking adhesives, I wonder if you could
just make a short hub that fit snugly over the stub of shaft with the
bottom of the hole in the hub milled flat to aid in alignment, and was
secured with a permanent anaerobic adhesive.

LLoyd

I seem to be missing the thread with details on the current resolver
connection, but per the link I did see to the resolver it is a shaft
connected device, so if the resolver shaft is connected to the motor,
getting a shaft for an encoder connected to the motor should be simple
enough.

If the resolver is a $1,400 piece as the link indicates, I'm sure Iggy
can sell it for far more than the cost of the encoder and materials to
mount it.

On 2010-08-04, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4c596f58$0
:

Yes, however it is of little benefit on the RT, with the resolver on
the
servo shaft, where a given servo shaft position equates to some 90
possible RT positions. If the resolver were connected directly to the
RT
it might provide some benefit over and encoder, but not when mounted to
the servo. In this case I'd recommend Iggy just replace the resolver
with another encoder, and sell the resolver to someone who needs it for
a tidy profit.


I wonder if that might be a way to "remote" an encoder. Make the
resolver into half a SlowSyn pair, and mount the encoder on the other
one. ???

I still have reservations about the difficulty of extending that motor's
shaft.

One thought came to mind, Ig:

I know there's a scant 1/8" of shaft "showing" past the bearing, but
given the almost vanishingly small load that extension will be under, and
given the quality of modern metalworking adhesives, I wonder if you could
just make a short hub that fit snugly over the stub of shaft with the
bottom of the hole in the hub milled flat to aid in alignment, and was
secured with a permanent anaerobic adhesive.


Lloyd, I bought a resolver to encoder converter from Jon, I will
simply mount it in the cabinet and it will be a done deal.

It was, possibly, not the best decision in terms of money, but in any
case, both ways (new encoder or Jon's converter) would give me a solid,
working solution. I think that I could have sold this resolver on ebay
for $175. Too bad, I cannot be perfect every time.

i

On 2010-08-04, Pete C. wrote:

"Lloyd E. Sponenburgh" wrote:

"Pete C." fired this volley in news:4c596f58$0
:

Yes, however it is of little benefit on the RT, with the resolver on
the
servo shaft, where a given servo shaft position equates to some 90
possible RT positions. If the resolver were connected directly to the
RT
it might provide some benefit over and encoder, but not when mounted to
the servo. In this case I'd recommend Iggy just replace the resolver
with another encoder, and sell the resolver to someone who needs it for
a tidy profit.


I wonder if that might be a way to "remote" an encoder. Make the
resolver into half a SlowSyn pair, and mount the encoder on the other
one. ???

I still have reservations about the difficulty of extending that motor's
shaft.

One thought came to mind, Ig:

I know there's a scant 1/8" of shaft "showing" past the bearing, but
given the almost vanishingly small load that extension will be under, and
given the quality of modern metalworking adhesives, I wonder if you could
just make a short hub that fit snugly over the stub of shaft with the
bottom of the hole in the hub milled flat to aid in alignment, and was
secured with a permanent anaerobic adhesive.

LLoyd

I seem to be missing the thread with details on the current resolver
connection, but per the link I did see to the resolver it is a shaft
connected device, so if the resolver shaft is connected to the motor,
getting a shaft for an encoder connected to the motor should be simple
enough.

If the resolver is a $1,400 piece as the link indicates, I'm sure Iggy
can sell it for far more than the cost of the encoder and materials to
mount it.

Pete, it is too late, I already bought a converter. Both solutions are
not bad. The converter solution involves zero hardware modifications
to the rotary table, but costs $150 more. It is possibly slightly
sub-optimal, but it is very straightforward.

i

On 2010-08-05, Jon Elson wrote:
Ignoramus30382 wrote:

I think that I could have sold this resolver on ebay
for $175. Too bad, I cannot be perfect every time.

I wouldn't count on it. I got two Harowe Controls Harosyn resolvers in
excellent but probably used condition for $25 plus shipping in two
different auctions.

I just saw a almost the same model by Harowe sell for $175.

I have seen them listed much higher, but don't know if they actually
sold for more. I definitely would not count on such a specialized
item bringing in a lot of money. On the other hand, I have sold
stuff on eBay that I literally pulled out of a dumpster for
hundreds! I had a massively modified DeVry 35mm movie camera from
the 1940's that went for something like $264, and some 30+ year old
microfiche from IBM field service that the IBM corporate historian
bought for $500! You NEVER know what something is worth to somebody
else.

Yep, many great examples abound.

Anyway, I am not losing my sleep over this and I will treat it as a
learning experience.

i

Pete C. wrote:


The idea that after missing some pulses the resolver will recover
absolute position eventually is pretty useless in this application,
since you have something like a 90:1 drive ratio to the table, and
knowing the motor is at position X tells you nothing about the position
of the RT. If you loose pulses your RT will remain off until you re-home
it. You should also not have any noise issues if you use shielded
cables, and ideally differential line drivers and receivers.

Actually, if noise has caused some error in the solution of the equation
and then the noise abates, the resolver converter WILL correct the error
and produce sufficient quadrature counts to get the computer back to the
exact correct encoder count. Now, if the computer has counted invalid
encoder counts due to electrical noise, that will not be corrected, but
it is the same situation as noise on traditional encoder circuits. I
don't see the difference there. Since Iggy will be putting a
differential-out resolver converter in the same cabinet as the
differential-input encoder counter, the chance of counting errors
between them is extremely unlikely.

The only way the resolver converter will permanently mess up is if the
noise is so great that it starts reading 180 degrees out of sync with
the resolver. Then when the noise clears up, it could correct position
going around the wrong way, or have lost entire revolutions of the
resolver. In this case, the noise problem must be corrected.

The resolver provides a unique reading at any rotation, and the
converter tracks that position. It does not produce "pulses" and
therefore cannot "miss some pulses".

Jon

Ignoramus16841 wrote:

On 2010-08-05, Jon Elson wrote:
Ignoramus30382 wrote:

I think that I could have sold this resolver on ebay
for $175. Too bad, I cannot be perfect every time.

I wouldn't count on it. I got two Harowe Controls Harosyn resolvers in
excellent but probably used condition for $25 plus shipping in two
different auctions.

I just saw a almost the same model by Harowe sell for $175.

I have seen them listed much higher, but don't know if they actually
sold for more. I definitely would not count on such a specialized
item bringing in a lot of money. On the other hand, I have sold
stuff on eBay that I literally pulled out of a dumpster for
hundreds! I had a massively modified DeVry 35mm movie camera from
the 1940's that went for something like $264, and some 30+ year old
microfiche from IBM field service that the IBM corporate historian
bought for $500! You NEVER know what something is worth to somebody
else.

Yep, many great examples abound.

Anyway, I am not losing my sleep over this and I will treat it as a
learning experience.

i

Yep, it will work fine. I just would have gone the USD encoder route for
consistency between axes as well as the machining challenge of adapting
the encoder to the motor.