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Discussion in 'General Electronics Discussion' started by Mathew, Sep 2, 2019.

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  1. Mathew


    Aug 20, 2019
    Hello. I’m searching for a SPCO/SPTT (SPDT) switch with a stable off position in the centre which is normally open, so that it resilience back to the off-position just like a NO push-button switch does.

    I’m also searching for a double DPST switch (Equivalent to two DPST switches controlled by a single mechanism).

    Any suggestions on where I can find this?
    Last edited: Sep 2, 2019
  2. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Any idea what physical size is acceptable? Contact voltage and current ratings?

    Toggle switches with a spring-return to center-off position are commonly available as DPST and DPDT two or three position switches. The ones that return the switch to the centered position when released are identified in catalogs as (ON)-OFF-(ON) where the parenthesis indicate momentary positions. Less common are two-position switches identified as (ON)-OFF. Check an online catalog by any international electronics distributor such as DigiKey or Newark or Jameco or Allied Electronics or Farnell element14 and many others. Let Google be your best friend in finding what you want.

    BTW, WTF does "SPCO/SPTT (DPDT) switch" mean? Single pole, double throw (SPDT) and double pole, double throw (DPDT) are commonly used switch descriptions, but I have personally never heard of SPCO or SPTT, having led a sheltered life here in the United States of America for the past seventy-five plus years. Please enlighten me.
    Harald Kapp likes this.
  3. Mathew


    Aug 20, 2019
    SPCO = single pole, centre off or single pole changeover and SPTT = Single Pole, Triple Throw. SPCO and SPTT switches are equal to a SPDT switch but specified with a centre off position, which some SPDT switches doesn’t have, so SPDT is a more general term.

    The physical size of the switches has to be pretty small, about .4” maximum. I will power this circuit with a 9V PP3 lithium battery, so the voltage and current will be fairly low.

    What I’m actually looking for is a switch like this with a spring return to the centre off position. So a normally open DPDT switch controlled by four mechanisms.

    Like this:
    ∷∷∷∷ ⇧∷∷∷∷∷
    ON ⇦ OFF ⇨ ON
    ∷∷∷∷ ⇩∷∷∷∷∷
    Last edited: Sep 2, 2019
  4. Minder


    Apr 24, 2015
    The Telemecanique ZB2B series of panel mount switches have a L-R spring return to centre version, you can add switch sections as needed.
    They are now second sourced out of China so you can get them on ebay if needed.
    If the right type, I have quite a few surplus, I believe I still have that version.
    If you want all four quadrants, you need a Joystick version of these.
    hevans1944 likes this.
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