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Discussion in 'Electronic Design' started by John Larkin, Nov 13, 2007.

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  1. John Larkin

    John Larkin Guest

  2. Jim Stewart

    Jim Stewart Guest

  3. John Larkin

    John Larkin Guest

    I think the dual is 17 cents by the reel.

    I like the input pulldown, for before uP ports are configured.

  4. John Fields

    John Fields Guest

  5. Sort of 1/4 of a ULN2803 or 28% of a ULN2003 (at several times the
    price) for low voltage output applications.

    Best regards,
    Spehro Pefhany
  6. legg

    legg Guest

  7. Hot Jock

    Hot Jock Guest

  8. Does that mean that there is no body diode in those parts? That could
    be an interesting feature.

    Best regards,
    Spehro Pefhany
  9. John Larkin

    John Larkin Guest

    I'm driving tiny relays and don't want the 0.6 volt drop of a
    Darlington. I also want them to drop out fast, so the zener is better
    than a clamp diode.

    Cute little gadget.

  10. John Larkin

    John Larkin Guest

    Looks like two identical, isolated chips inside. I'll break one open
    and see.

  11. Yup, although the clamp diode will work just as well, depending on
    what you clamp it to.
    So far I've managed to avoid 5V relays most of the time. Last gadget
    with 5V latching relays used emitter-follower drive on the coils (so
    no diodes required and no base resistors). There was enough margin
    with a regulated supply.

    Best regards,
    Spehro Pefhany
  12. legg

    legg Guest

    I think you're asking too much of this data sheet, if you want to know
    things like inter-device isolation (drawn as seperate sources) or
    actual surge capability in any direction. I don't know what the author
    was using for brains.

    The SOA chart doesn't extend operation to the zener clamping voltage,
    so who's to know what the hell it does.

    It's a good attempt to reduce parts count in an application that most
    designers would try to avoid altogether ie use of electromechanical

  13. John Larkin

    John Larkin Guest

    Well, I have a 3.3 volt cpu and 5-volt relays here! I'm using some
    cute little Fujitsu dpdt telecom relays. They pull in and drop out in
    under a millisecond.

  14. John Larkin

    John Larkin Guest

    The tiny dpdt relays we're using here have 30 milliohm on resistance,
    signal response, 1 amp capacity, and 0.25 pF open capacitance. Find me
    a semiconductor that will do that for $3!

  15. On Tue, 13 Nov 2007 09:29:27 -0800, in John

    I always liked these
    and from their blurb

    "The company owns the freehold of its main two acre site and factory,
    with no mortgages or borrowings, so we have a very strong financial

  16. John Larkin

    John Larkin Guest

    That's novel, to not be deep in debt.

    I avoid reeds. They seem to fail a lot more often, in real life, than
    they're supposed to.

    These are nice:

    The latching ones are great for microvolt stuff... no thermal emf's.

  17. Jamie

    Jamie Guest

    Hmm, were you using DC relays with internal diodes? Some have them which
    stands for the reason of the + & - marking found on some.
    Other wise, I don't see how the transistors would have survived unless
    the bias control was ramping?
  18. Think about it.. emitter follower.

    Best regards,
    Spehro Pefhany
  19. Jamie

    Jamie Guest

    Yes, I have.. and still..
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