double ended 360 degree pot sources.

[Jamie]

We are in the middle of re-manufacturing some equipment and most
of it is going fine, however, we decided to use what appears to be a
custom potentiometer which has a long shaft on one side and a shorter
one on the other side.

We had in stock a couple of claristat (now HoneyWell)
5k 360 degree mechanical rotation wire wound pots. There isn't
much special about these except for the fact they are larger form
factor and have a center tap at mid point on the pot, which we don't
need. This pot also have a double ended shaft which is what we really
need the most here, due to mechanical coupling of where it must go.

We found out today, these pots are now obsolete, however, that is what
was told to us by a vender. I found later today they are
being offered all over the place with a very high price tag!

One place I located could deliver one for $500, and yet another
site offered it for $1250 each.. It's obvious beyond any doubt that this
must be a price to have a minimum manufactured. I can only picture this
being farmed out to a chinese sweatshop with huge profits.

So, we have to find an alternative to this part.

Has any of you seen double ended HALL angle sensors or
pots that do continuous rotation with a very reasonable dead
zone ?

The shaft should be 1/4 inch but we could alter that it needed.

If there is no resolve for this, I will have to resort to a
high res ABS encoder (gray code) with a hollow shaft.

Jamie

[mrob...@att.net]

Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:
> We found out today, these pots are now obsolete, however, that is what
> was told to us by a vender.

It's probably worth asking Honeywell directly. There is a pretty good
chance that they will tell you either "no" or "we will restart the
production line for a million bucks", but there's a small chance they'll
say "yeah, we don't make those anymore, but our other customers have
changed over to the 123 series from Acme".

> One place I located could deliver one for $500, and yet another site
> offered it for $1250 each.. It's obvious beyond any doubt that this
> must be a price to have a minimum manufactured.

They also could be small quantities of surplus or new old stock units.
Some vendors will price them that way, especially if they have any idea
that the part was ever used in a highly regulated design (aerospace,
military). Buying a $500 pot might make sense for low-volume repairs of
a device that there is a contractual obligation to support; $500
wouldn't even begin to cover the engineering time and paperwork to
certify a different part.

> Has any of you seen double ended HALL angle sensors or pots that do
> continuous rotation with a very reasonable dead zone ?
>
> The shaft should be 1/4 inch but we could alter that it needed.

Hollow shaft pots exist; you could install your own shaft in the
configuration needed. Finding hollow shaft 360 degree pots is a little
harder but there are least datasheets for some of them:

Expensive *looking* one with 355 degrees:
http://sensors.apitech.com/product/hspps1250diamtriple22.asp

One with continuous mechanical and 340 degree electrical:
http://www.contelec.ch/fileadmin/user_upload/contelec/Downloads/Datenblaetter/Englisch/Potentiometer_Leitplastik/WAL305_e.pdf

More from the same company here:
http://www.contelec.ch/en/produkte.html?action=list&typ=Leitplastik

One with 360 degree mechanical and either 330 or 360 degree
electrical (note the handy 1200 piece minimum):
http://www.alps.com/WebObjects/catalog.woa/E/HTML/Sensor/Position/RDC80/RDC80_list.html

Inexpensive *looking* one with 270 degrees:
http://www.aisensors.com/RotaryPositionDataSheetsPart1/HWL60.pdf

I don't know if any of these parts suck or not; I just Googled them up.

Standard disclaimers apply; I don't get money or other consideration
from any companies mentioned.

Matt Roberds

[Spehro Pefhany]

On Thu, 25 Apr 2013 23:23:56 -0400, Jamie
<jamie_ka1lpa_not_v...@charter.net> wrote:

>
> We are in the middle of re-manufacturing some equipment and most
>of it is going fine, however, we decided to use what appears to be a
>custom potentiometer which has a long shaft on one side and a shorter
>one on the other side.
>
> We had in stock a couple of claristat (now HoneyWell)
>5k 360 degree mechanical rotation wire wound pots. There isn't
>much special about these except for the fact they are larger form
>factor and have a center tap at mid point on the pot, which we don't
>need. This pot also have a double ended shaft which is what we really
>need the most here, due to mechanical coupling of where it must go.
>
> We found out today, these pots are now obsolete, however, that is what
>was told to us by a vender. I found later today they are
>being offered all over the place with a very high price tag!
>
> One place I located could deliver one for $500, and yet another
>site offered it for $1250 each.. It's obvious beyond any doubt that this
>must be a price to have a minimum manufactured. I can only picture this
>being farmed out to a chinese sweatshop with huge profits.

Rather hard to make huge profits on a one-off $500 custom order, in
fact it's almost guaranteed to lose money. They're pretty much telling
you to get lost.

> So, we have to find an alternative to this part.
>
> Has any of you seen double ended HALL angle sensors or
>pots that do continuous rotation with a very reasonable dead
>zone ?
>
> The shaft should be 1/4 inch but we could alter that it needed.
>
> If there is no resolve for this, I will have to resort to a
>high res ABS encoder (gray code) with a hollow shaft.
>
>Jamie

Have you tried using a search engine, such as Google?


Surplus 2K pots for only $50: (dual 1/8 OD x 1/4" shafts)
http://www.surplussales.com/Images/Potentiometers/ClampingMount/rwv-pvr11-k17_.jpg

New Indian ones, probably not too expensive (6mm shafts)
http://pankaj.com/index.php/type-ss-50.html

Surplus 1K CT pots withy dual shafts (6 available, it says)
http://www.ebay.com/itm/POTENTIOMETER-HELIPOT-1K-500-OHMS-CT-DUAL-SHAFT-/260700557442

[Spehro Pefhany]

On Thu, 25 Apr 2013 23:23:56 -0400, Jamie
<jamie_ka1lpa_not_v...@charter.net> wrote:

(resent with correct subject line)

> We are in the middle of re-manufacturing some equipment and most
>of it is going fine, however, we decided to use what appears to be a
>custom potentiometer which has a long shaft on one side and a shorter
>one on the other side.
>
> We had in stock a couple of claristat (now HoneyWell)
>5k 360 degree mechanical rotation wire wound pots. There isn't
>much special about these except for the fact they are larger form
>factor and have a center tap at mid point on the pot, which we don't
>need. This pot also have a double ended shaft which is what we really
>need the most here, due to mechanical coupling of where it must go.
>
> We found out today, these pots are now obsolete, however, that is what
>was told to us by a vender. I found later today they are
>being offered all over the place with a very high price tag!
>
> One place I located could deliver one for $500, and yet another
>site offered it for $1250 each.. It's obvious beyond any doubt that this
>must be a price to have a minimum manufactured. I can only picture this
>being farmed out to a chinese sweatshop with huge profits.

Rather hard to make huge profits on a one-off $500 custom order, in
fact it's almost guaranteed to lose money. They're pretty much telling
you to get lost.

> So, we have to find an alternative to this part.
>
> Has any of you seen double ended HALL angle sensors or
>pots that do continuous rotation with a very reasonable dead
>zone ?
>
> The shaft should be 1/4 inch but we could alter that it needed.
>
> If there is no resolve for this, I will have to resort to a
>high res ABS encoder (gray code) with a hollow shaft.
>
>Jamie

[Jamie]

our problem is we need to source these to be able to get these later..

For a couple of service jobs, getting someone's old stash from E-Bay
or where ever would be ok.

I would rather say away from ganged pots, the space where this must
fit is tight. But that was a good fine however, you did better than I
did..

Thanks.
Jamie

[Jamie]

yes, I found many of those when I was doing my search. We need one that
is designed for industrial use, since it is going to take a little
beating..

Many of them are plastic resistors and I've found those to lose their
linearity over use, way before they actually get mechanically worn out.

I've look around some more today and called some people, it looks like
we may need to rethink that section and employ a different technique.

So, we experimented with a linear inductive prox and a eccentric cam
wheel that can be mounted on a shaft. The problem with this is, this
section of the equipment must be very accurate and maintain to prevent
erratic sensing.

After looking at absolute encoders, it was determined that machine
vibration in this section may be short lived.

Thanks

jamie

[Joe Gwinn]

In article <hrEet.315$VE....@newsfe25.iad>, Jamie

There are lots of linear and angular displacement sensors that are
suitable for use on machines, vibration al all, with very high
accuracy. What are you trying to do? How good does it need to be?


Joe Gwinn

[mrob...@att.net]

Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:
> yes, I found many of those when I was doing my search. We need one
> that is designed for industrial use, since it is going to take a
> little beating..

I guess I need to recalibrate my approach, here.

There seem to be two kinds of "component selection" posts lately. One
is where someone seems to be aware of all the major alternatives, and is
asking just to see what is popular, or to make sure they haven't left
something out or not heard about a new part, or is looking for "gotchas"
with a specific approach. It looks to me like these kinds of posts
result in more useful information, more quickly, for the original
poster.

The other kind is where someone wants help selecting a specific part
number, but only puts about 25% of their requirements in the first post.
When people respond with suggestions and ideas, the response is "that
won't work because of additional requirement X". I can understand not
wanting to spill *all* the beans for commercial reasons, but defining
requirements via "20 Questions" is not so much fun if somebody is
working for free.

Matt Roberds

[Tauno Voipio]

This might be a job for a synchro or resolver, though not cheap. They
work even as propeller pitch sensors on big radial engines.

--

Tauno Voipio

[Michael A. Terrell]

He thinks the prices he was quoted were high. The 360� pots used for
Chromakey were US $1400, 30 years ago. He bitches about plastic pot
elements. Traditional pots wear much faster, and produce more noise.

[Jamie]

ok, I really didn't understand the bulk of what you were trying to
convey, but what ever..

An alternate design has been agreed on. We're going to use a analog
inductive prox with a 5 mm range and a eccentric target. Total cost
for the prox is under $100 if we buy 10 or more and this technology
does not appear like it's going to be obsolete any time soon. Plus it
gives us a better results over all including life expectancy.

Thanks to all that that helped out.

Jamie

[Bill Sloman]

http://au.element14.com/avago-technologies/aedb-9140-a06/en-3ch-500cpr-metal-cw-28mm-1-4in/dp/1161085

http://www.farnell.com/datasheets/20523.pdf

It's an Avago metal code wheel for a 1/4 inch - 6.35mm - shaft with a three channel encoder that sits on one side of the code wheel. One of the channels detects an index slot, once per revolution.

Less messy than a cam and a linear displacement measuring system for finding out where the cam is.

--
Bill Sloman, Sydney

[Jamie]

if I was to do that, we would be using an enclosed unit with hollow
shaft, which we can get all day long from many places. Dynapar, redlion
are some examples.
The problem with the one you suggested is, that it's open frame, that
would never work. Plus it is too low of PPR count.

We have gone with the 5 mm distance analog prox with an eccentric
disc on the through shaft. Environmentally happier..

Jamie

[josephkk]

Maybe you should look for rotary variable differential transformer (the
rotary cousin to a LVDT). Or perhaps a resolver (see synchro as well).

?-)

[Syd Rumpo]

On 26/04/2013 04:23, Jamie wrote:
>
<snipped>
>
I have a couple of Penny and Giles conductive plastic 360' servo pots
with 1/4" double ended shaft. These are old, but maybe they still make
them or similar.

Cheers
--
Syd