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double ended 360 degree pot sources.

Discussion in 'Electronic Design' started by Jamie, Apr 26, 2013.

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  1. Jamie

    Jamie Guest

    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
     
  2. Guest

    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".
    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.
    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/us...glisch/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
     
  3. 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.
    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
     
  4. On Thu, 25 Apr 2013 23:23:56 -0400, Jamie

    (resent with correct subject line)
    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.
    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
     
  5. Jamie

    Jamie Guest

    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
     
  6. Jamie

    Jamie Guest

    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
     
  7. Guest

    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
     
  8. Tauno Voipio

    Tauno Voipio Guest


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

    Jamie Guest

    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
     
  10. Bill Sloman

    Bill Sloman Guest

    http://au.element14.com/avago-techn.../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.
     
  11. Jamie

    Jamie Guest

    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
     
  12. josephkk

    josephkk Guest

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

    ?-)
     
  13. Syd Rumpo

    Syd Rumpo Guest

    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
     
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