Are bifurcated relay contacts any better than paired contacts?

Discussion in 'General Technical Questions and Answers' started by W0BTU, Jan 23, 2011.

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  1. W0BTU

    W0BTU Ham Member QRZ Page

    Ok, here's one for you relay experts.

    Looking at some relay contact tech data on the P&B/Tyco web site, I came across a statement that I don't quite get:
    Twin contact, bifurcated contact:
    Contact with two simultaneously operating contact points. Twin contacts increase the contact reliability considerably, especially when switching low currents and voltages (dry circuits) and/or are used for reduction of contact resistance. Bifurcated contacts are twin contacts with the two contact points on one contact member (contact blade).
    {Another way of understanding a bifurcated contact is that it is a forked contact, with a contact at the end of each fork.}
    Ok, that being assumed to be correct...

    What's the difference in dry-circuit contact reliability when purchasing a DPDT bifurcated contact relay, or simply pairing the contacts on an ordinary 4PDT relay (wiring it as a DPDT)?

    Of course, the contact material is important, too. But that aside, are bifurcated relay contacts any better than paired contacts?

    I'll bet they aren't.
     
  2. K8ERV

    K8ERV QRZ Member QRZ Page

    The problem is that the contact pressure for each one is about 1/2 of the total, and contact pressure is VERY important in high-current switches.

    TOM K8ERV Montrose Colo
     
  3. K8MHZ

    K8MHZ Ham Member QRZ Page

  4. W0BTU

    W0BTU Ham Member QRZ Page

    Thanks. That was an interesting read. However, "dry circuit" by its very definition describes a low current switch. Even no current.

    "Dry contact" refers to a contact of a relay which does not make or break a current.
     
    Last edited: Jan 23, 2011
  5. W8JI

    W8JI Ham Member QRZ Page

    Mike,

    The real issue for receiving is using the lowest possible current, gold flash, and nearly sealed relays.

    I go many years without relay problems using standard 1 amp or 2 amp DPDT dip relays, while using one pole of the relay. The only failures I've ever had are from lighting, and most of them are open coils.

    Unless they change the contact design, bifurcated contact are no better than pairing pairs.

    Tom
     
  6. W0BTU

    W0BTU Ham Member QRZ Page

    That's what I thought. Thanks! Case closed. :)
     
  7. W0BTU

    W0BTU Ham Member QRZ Page

    Well, if I sounded argumentative, I didn't mean to. :)

    Funny you should say that. I was just inquiring about the flux flow vs. shape, etc. in toroidal vs. multi-aperture ferrite cores from the manufacturer.
     
  8. W0BTU

    W0BTU Ham Member QRZ Page

    Respectfully, you just don't know some of the people here. While they may indeed be in the minority, there are some manufacturers, owners of highly respected companies, and just plain technical geniuses here. And they regularly contribute information here that you will never find in any book, or from some manufacturers.

    I may very well have found the answer to my question from P&B/Tyco. But I think I got it here. :)

    And I happen to own a company that manufactures things. But that doesn't in itself mean I know what I'm doing, that others aren't smarter than me.
     
    Last edited: Jan 24, 2011
  9. K8ERV

    K8ERV QRZ Member QRZ Page

    Q&A here may help others. A call to the mfr doesn't.

    TOM K8ERV Montrose Colo
     
  10. W8JI

    W8JI Ham Member QRZ Page

    I agree. There is no reason to get nasty with Mike.

    Plus I've dealt with manufacturers for years specifically related to the environment Mike is worried about. I know what he is trying to avoid, it isn't a new problem.

    The solutions offered by P&B and others are to increase contact pressure, use multiple smaller contacts in parallel, or bifurcated contacts if available. They recommend gold flash also.

    If Mike just uses a standard small signal sealed relay most problems will go away.

    73 Tom
     
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