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Snubber Selection

Discussion in 'Electronic Design' started by [email protected], May 28, 2008.

  1. Guest

    Hi,

    I have a 24VDC relay, and I need a way to supress the transient caused
    by it switching after you remove the load.

    I understand that my best choices are an MOV, a flyback diode
    (schottky, I assume?), and a transorb.

    I put a scope on it, and the transient spikes at around 1200 volts.

    Which of the three options is the 'best'. Which is least likely to
    ever burn out? What specs should I be paying attention to when I pick
    the component?

    Thanks,
    Dan
     
  2. Phil Allison

    Phil Allison Guest


    ** Frightening.

    ** MOVs are rugged and fairly cheap.

    The voltage rating depends on what ( semi?) is driving the relay coil.

    At a guess, a 50 volt MOV would be a good bet and allow the relay to
    de-energise very quickly.

    BTW:

    there is no need to use a schottky diode.



    ....... Phil
     
  3. On Wed, 28 May 2008 06:23:57 -0700 (PDT), in sci.electronics.design
    someone posted this app note a few days ago
    http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3311.pdf


    martin
     
  4. Jamie

    Jamie Guest

    mov's only take a wack x number of times before they short.
    use a bidiretcional TVS (Transient Voltage Suppressor) diode or schottky
    diode.

    http://webpages.charter.net/jamie_5"
     
  5. Phil Allison

    Phil Allison Guest

    "Jamie the Jerk Off "
    ** Bollocks.


    ** There is no advantage here in using schottky.

    You fucking ass.



    ...... Phil
     
  6. Bob Eld

    Bob Eld Guest

    The best solution depends on the problem you want to correct. The simplest
    solution is to place a plain old diode like a 1N4002 back biased around the
    relay coil. The max current the diode will see on ring off is the current
    that was flowing when the coil was energized. And, it only flows in the
    diode for a short duration on turn off. The reverse voltage on the diode is
    the same as the coil, 24 Volts in this case. There is not much of a
    requirement for this diode.

    The energy the diode is controlling is the energy stored in the coil's
    inductance. 1/2LI^2, which ain't much. That energy is dissipated in the
    coil's resistance on turn off. The diode is just redirecting it back into
    the coil.
     
  7. Guest

  8. Jamie

    Jamie Guest

    What an ass you are, the advantage is that schottky has a
    lower threshold and is easier to get.
    Since this is a DC relay, either would work, it's what easier
    for you to obtain.

    My self, I've found integrated snubbers to work nicely. they suppress
    the pulse to help reduce RFI nicely.

    Using DIodes will still give you a noise generation problem but will
    protect the circuit.

    Have a good day Phill as always.


    http://webpages.charter.net/jamie_5"
     
  9. Rich Grise

    Rich Grise Guest

    No, MOVs are crap. One place where I was working when they invented the
    Transzorb issued ECOs to take out all of the MOVs and replace them
    with Transzorbs.
    If you want a fast drop-out, you want to let the spike go as high as
    it can, safely. (the amplitude of the spike is determined by how fast
    the field collapses.)

    Hope This Helps!
    Rich
     
  10. Guest

    So, it sounds like I don't want to use an MOV.

    I didn't see any negative voltage, so I'm guessing I don't need a
    transorb. So, by process of elimination, I'm going to go with either a
    plain old diode or a schottky. As the schottkys seem to have faster
    switching time, I'm goign to go with one of them.

    Thanks!
     
  11. Guest

    Does anyone have any suggestions on a part or series? There's so many
    to choose from... (It's for a 24VDC relay)
     
  12. Jamie

    Jamie Guest

    A basic 1 amp 50 v will do it.

    Select what ever package fits your needs.





    --
    "I'd rather have a bottle in front of me than a frontal lobotomy"

    "Daily Thought:

    SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
    THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
    http://webpages.charter.net/jamie_5"
     
  13. Phil Allison

    Phil Allison Guest

    "Jamie the Jerk Off "

    ** What a FUCKING ASS you are !!

    There is no advantage in having a lower threshold here and schottkys are
    MORE expensive by far than ordinary silicon diodes and harder to find.

    Fuckwit.


    ....... Phil
     
  14. Phil Allison

    Phil Allison Guest

    <>


    So, it sounds like I don't want to use an MOV.


    ** Yo uare being fed bollocks by complete asses.

    I didn't see any negative voltage, so I'm guessing I don't need a
    transorb. So, by process of elimination, I'm going to go with either a
    plain old diode or a schottky. As the schottkys seem to have faster
    switching time, I'm going to go with one of them.


    ** You must be a fucking idiot.

    Ultra fast switching is irrelevant to suppressing a relay - plus using a
    diode slows the relay going off .

    Can cause damage to the relay contacts.



    ....... Phil
     
  15. Phil Allison

    Phil Allison Guest

    <>

    Does anyone have any suggestions on a part or series? There's so many
    to choose from... (It's for a 24VDC relay)


    ** What current rating is the coil ?

    24 volt relays vary a lot.




    ....... Phil
     
  16. Phil Allison

    Phil Allison Guest

    "Jamie the FUCKWIT Jerk Off "


    ** Oh my god - what an utter CRETIN !!!

    Where Jamie works, all the inmates have straight jackets.




    ....... Phil
     
  17. Jamie

    Jamie Guest

    Oh really, you wouldn't do well where I work son.!



    http://webpages.charter.net/jamie_5"
     
  18. Jamie

    Jamie Guest

    yes Phill, please come back we miss you! Your bed is still
    waiting for you , straps and all.



    --
    "I'd rather have a bottle in front of me than a frontal lobotomy"

    "Daily Thought:

    SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
    THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
    http://webpages.charter.net/jamie_5"
     
  19. Phil Allison

    Phil Allison Guest

    "Jamie the FUCKWIT Jerk Off "


    ** Complete mental retard.

    What else would you expect from someone whose real name is " Maynard A.
    Philbrook " who works as a code scribbler and has the ham call sign
    KA1LPA.

    Lives in a dream world with no idea of his monumental ignorance.



    ...... Phil
     
  20. legg

    legg Guest

    This can hardly be an issue at the power levels and impedances being
    discussed here.

    RL
     
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