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very small mechanical latching relays

Discussion in 'Electronic Basics' started by Jon Slaughter, May 22, 2007.

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  1. Do they make very small mechanical relays(for switching very small currents
    and voltages) that also latch?

    Essentially I need a way to switch analog audio signals using a
    "non-envasive" method... which means no semi-conductors(theres a reason but
    don't bother asking... just assume its impossible and don't try to give
    reasons why it should matter cause I already know them).

    Obviously the coil is the issue but since the currents and voltages are very
    low I assume that the conductor for the switch can be small also and
    therefore one doesn't need such a large coil... or maybe theres some other
    mechanism for switching that could be used...

    What I want is for the switch to latch in the on or off state and need any
    power to hold that state. I believe this could be accomplished with springs
    or some other method of producing just enough friction to hold the switch in
    place.

    Any ideas?

    Thanks,
    Jon
     
  2. "Very samll" is not a dimension, but yes, they make small,
    magnetically latched relays with two coils. A pulse to one
    coil latches the relay, and a pulse to the second coil
    unlatches it.
    We need actual specifications, if we are to find you something.
    Here are some examples:
    http://pewa.panasonic.com/pcsd/product/sign/pdf_cat/sx.pdf
     
  3. a few volts which problem on average is < 1V(actually about 100mV on
    average) and the current is in the mA range if not smaller but probably
    smaller.
    I was hoping something a bit smaller than 1/2". I would be using a lot of
    these and the smaller the better.

    The idea is that I want to switch a couple of components into various
    configurations using a digital method instead of mechanical... right now I
    have 3x8 dip switches to do the switching and it requires that I change all
    the switches by handle to a specific setting that corresponds to some
    configuration. I just want to simply automate the switching so that
    different configurations can be had at a touch of a button.

    Ultimately it would be easier to use semiconductors but because this project
    might end up commerial and because its use in audio and the market I'm
    aiming for is very anal about solid state interfering with the quality that
    I would like to do this with mechanical relays. Of course the smaller the
    better for various reasons.

    Jon
     
  4. Sjouke Burry

    Sjouke Burry Guest

    If you use a reed relay, put a small magnet
    close to one end.
    It will make the contact sticky, and a reverse
    current will release the contact.
    You might google for "latching reed relay"
    I got 230 hits, the first one could be it.
     
  5. John Larkin

    John Larkin Guest

    Take a look at the Fujitsu FTR-B3G type parts, DPDT, in Mouser.
    Drop-in equivalents are available from Omron and NEC. They switch very
    fast (about a millisec) and seem very reliable.

    We use the single-coil version (bipolar drive) and drive the coil from
    a tiny-logic dual NOR gate.

    John
     
  6. John Fields

    John Fields Guest

     
  7. Thanks guys. These are a bit larger than I was hoping for but might work.
    I'll have to figure out something and might just go with fets, atleast for a
    prototype.

    Thanks,
    Jon
     
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