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Do Wiggle Stick Meters Wear Out?

Discussion in 'Electronic Repair' started by Watson A.Name - Watt Sun, Dark Remover, Dec 29, 2003.

  1. I read in alt.binaries.schematics.electronic that Chuck Harris
    Not really; you are on the right lines insofar as a low value of L/C
    make oscillation less likely, as I show below. But you haven't actually
    mentioned the key word. The crucial factor is the *resistance* of the
    coil, as I tried to indicate before. If R =>sqrt(L/C) the current won't
    oscillate. It didn't.
     
  2. I had to repair a taut band suspension because I had acceidentally
    trashed its mounting (don't ask). Fortunately, the band itself
    was intact and could be unsoldered from the remaining debris. It's
    not fun but is possible, more so I'd say than for a typical jeweled
    movement simply because there is not hairspring to cause problems.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
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  3. When in doubt, use a keeper. I've seen servo and stepper motor PM magnets die
    if the rotor is just pulled out.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

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  4. Chuck Harris

    Chuck Harris Guest

    Yes, but it also won't put much in the way of current into the
    coil. You might as well use a straight DC supply, and just press
    the button for an instant.

    I big honking diode would work better. Charge your capacitor up to
    400V or so, and dump it into a coil that has a diode in series.
    The current will quickly ramp up to some maximum value. There will
    be a nasty back emf spike, but such is life.

    -Chuck
     
  5. Jim Weir

    Jim Weir Guest

    Everything wears out. The Rockies and the Sierra are dwindling down at about an
    inch every 1000 years. If you mean in your lifetime, probably not unless you
    start to bang the needle off the peg every so often.

    Jim
     
  6. DarkMatter

    DarkMatter Guest

    I'm having a tough time with this one.
     
  7. In what way? :)

    I think one example was a "Slo-Syn" motor. I removed the rotor out of
    curiosity. When it was put back in, the motor had lost 75 percent of
    its torque. Definietly a weak magnet. I probably still have it and
    an identical good unit.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
    contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  8. DarkMatter

    DarkMatter Guest

    It was the sliding action, perhaps. I'm still finding it hard to
    believe that it just didn't get overheated, and went above it's curie
    point temperature, causing loss, and you didn't catch the torque loss.

    Are you saying that you made a before and after measurement with it,
    when you did it? Or was it "in for repair" already?
     
  9. I read in alt.binaries.schematics.electronic that Chuck Harris
    It put enough.
    Oh, yes A 4 A DC supply is much easier that a 34 mA one.
    This capacitor has infinite capacitance?
    I don't really think you understand what happens.
     
  10. Yes, at least by hand. I didn't actually use instruments. They were
    identical before, very different after. Neither was subjected to any
    abuse.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
    contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  11. Chuck Harris

    Chuck Harris Guest

    And who said it did?
    You think there won't be a back emf spike when the diode
    stops conducting? Hmmm?

    -Chuck Harris
     
  12. DarkMatter

    DarkMatter Guest

    I'd bet that a check on the "magnetized state" of the rotor would
    show that it had become magnetized thereby offsetting what work gets
    done upon re-assembled.

    If you demag the rotor, then return it, the torque should return.

    Just one possibility that immediately came to mind. I'm not saying
    that is what happened, just throwing it out to see who salutes it.
     
  13. DarkMatter

    DarkMatter Guest


    When one dumps a cap into a coil, there is a current inrush. When
    one attaches a constant voltage DC source to a coil, there is a
    current inrush, and then a standing magnetic field is exhibited until
    the source is removed.

    The collapse of the flux will be slower from the cap than if a DC
    source is applied, a standing field is exhibited, and then said source
    is immediately released. That second method will exhibit a MUCH
    higher slew rate on the collapsing flux, and a much higher potential
    will be "seen" at the coil terminals.

    A cap makes for a slow collapse, and the back emf is nowhere near as
    high. As the cap discharges, the voltage decreases to zero. The coil
    does not recharge the cap, even without the diode. At least not
    enough to make a difference. Ther are a few perturbations, but it
    looks similar to a slightly under damped feedback loop, with each
    reverb being vastly smaller than the previous...then to zero.
     
  14. Jim Adney

    Jim Adney Guest

    I don't claim to fully understand the cause, but I do know that it can
    certainly happen with certain kinds of magnets.

    Sturmey-Archer, the maker of the 3-speed bicycle hubs that you're
    probably familiar with, also made a hub with a generator built into
    it. If you pull the armature out of the multipole circular magnet it
    will lose most of its field. I've never done this, but I have the
    factory manuals that explain to only slip the armature out as you slip
    the keeper in.

    I also have a NOS magnet, shipped from the factory with a keeper in
    place.

    -
     
  15. Chuck Harris

    Chuck Harris Guest

    Damn! I wasted all that money going to engineering school!

    Inductors resist a change in current. When you apply a voltage to an
    inductor, the current is initially *zero* and it rises linearily until
    it reaches V/Rcoil, or the saturation of the core if you have one.

    When you clamp a charged capacitor to an inductor, you create a tank
    circuit. The capacitor and the inductor pass energy back and forth.
    They would do so forever, but for radiation losses, and losses in the
    coil and inductor.

    Either I am not understanding what you meant to say, or you need to
    study the basic circuit elements, and resonant circuits some more
    Mr. DarkMatter.

    -Chuck Harris
     
  16. DarkMatter

    DarkMatter Guest


    Take a look at the link I posted earlier in this thread, and you'll
    see (read and see) how important it is.

    Of course it is still valid. Valid for all magnetic media.

    Why else would we actually develop different magnetic alloys unless
    properties, and characterizations of any and all known and attainable
    principles were not the goal?
     
  17. DarkMatter

    DarkMatter Guest

    Losses, losses, losses. I think I said that.
     
  18. DarkMatter

    DarkMatter Guest


    It will cycle a few times, but will essentially stabilize at a DC
    voltage, with a standing field on the coil, and slowly leak down from
    there on high turn count, high DC resistance coils, and on low turn
    coils, even faster. Continuous self oscillation requires a pump.

    Resonate that.
     
  19. Yeah, I'd guess as much, now that I've read the other followup about a
    jeweled watch escapement moving back and forthe five times a second
    for decades.

    About the mountains.. I was watching some program on PBS this morning
    that went along with a guy who survived Mt. St. Helens "eruption", if
    you can call seven tenths of a cubic mile of a mountain blowing away
    an eruption. ;-)

    They took a hike back around (what's left of) the mountain. After
    almost 24 years, the landscape still looks as bleak as the moon in
    some places.

    --
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    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
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  20. DarkMatter

    DarkMatter Guest

    Yet another man was the last to be heard from at the time of the
    eruption.

    He was on the radio phone with:

    "Yes, there it goes... Yes, it's very big... Yes, it's going to get
    me too..."

    Poor guy. Fertilizer for thinking he was far enough away at five
    miles.

    Trees combed over like a giant hair brush came through for miles.

    Atomic blast force levels many times that of hiroshima, or even our
    biggest Cobalt Hydrogen devices ever got... many times over.
     
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