Results 1 to 8 of 8

Thread: SPDT or DPDT

  1. #1
    150+ Forum Groupie
    Join Date
    Oct 2007
    Location
    N Ireland
    Posts
    251
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    SPDT or DPDT

    Ok a real newbie question. Attempting my first panels. I read in some post (somewhere) that there was in fact little difference in SPDT switches and DPDT switches. This contributor suggested that the second pole in a DPDT switch was rarely used. Is this correct. If not what is the second pole used for? I am assuming these switches give one set of parameters when "up" and a different set when "down".

  2. #2
    150+ Forum Groupie andarlite's Avatar
    Join Date
    May 2007
    Location
    Mississauga, Ontario, Canada
    Posts
    260
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    A DPDT switch is just 2 SPDT on a single switch. This is just an example, but let's say you have a SPDT switch to turn on your right fuel pump and another SPDT switch to turn on your left fuel pump. If you are always turning both on/off at the same time time (and you're tired of always having to flip 2 switches), you could get rid of the SPDT switches and wire both fuel pumps to a DPDT switch. Now by flipping one switch, you turn on/off both fuel pumps.

    Regards,
    Henry

  3. #3
    150+ Forum Groupie
    Join Date
    Oct 2007
    Location
    N Ireland
    Posts
    251
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    Thank you for your explanation. I think I will stick to SPST and SPDT for now!! At least until I get a little more experience. Currently I am building a "PedoHead" which is a mixture of pedestal and overhead (overhead just not viable at the moment). This will simulate all the controls I need/want at the moment. I do not wish to start from cold and dark just now. Instead I start at gate with engines running but on my "pedohead" I will have radios, lights, Radar Contact panel, FDC panel, MZALFOTRI (for PMDG 737), 3 Go Flight Units etc. Lots of work ahead.
    Bill

  4. #4
    150+ Forum Groupie


    steveeverson's Avatar
    Join Date
    Nov 2007
    Location
    Lancashire UK
    Posts
    210
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    Smile im sure you know this already but gets it clear in my own mind!

    SPST - single pole,single throw (one position switch eg on-off)
    SPDT - single pole,double throw (2 position switch eg on,off,auto)

    DPST- double pole,single throw (basically 2x SPST connected to same switch lever)
    DPDT- double pole, double throw(2x SPDT on same switch lever)

    I guess you could have a triple TPST or TPDT.....
    Steve
    another bedroom boeing.....

  5. #5
    150+ Forum Groupie
    Join Date
    Apr 2007
    Location
    Alberta, Canada
    Posts
    213
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    The other reeason some people use a DPDT switch is when they use seperately powered annunciators. The DPDT allows two circuits to be used without interfering with each other.

    Rob

  6. #6
    2000+ Poster - Never Leaves the Sim Michael Carter's Avatar
    Join Date
    Oct 2006
    Location
    Southern Illinois, USA
    Posts
    2,887
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    I use those. One side for the annunciator, the other side for signal.

    And there are switches with as many as eight poles. The fire handles on the 727 and 737-200 have very long push-pull type multiple pole swithes.
    Boeing Skunk Works
    Remember...140, 250, and REALLY FAST!

    We don't need no stinkin' ETOPS!



    Powered by FS9 & BOEING

  7. #7
    1000+ Poster - Fantastic Contributor Tomlin's Avatar
    Join Date
    Nov 2005
    Location
    Waycross, GA
    Posts
    1,027
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    I plan to use these for the Avionics and Battery switches for my Learjet sim. One side of the switch will be connected to the REAL power and the other side will be connected to the SIMULATED power/Avionics (FS) and this will prevent the screens from showing the LCD backlighting when the avionics arent turned on in the sim. Also, this allows for a person to build in some electrical logic without having to use PM Systems, such as how the BATT switch has to be on in order for the Avionics Master to be effective.
    Eric Tomlin-
    Learjet 45 Builder
    www.flightlevel180.org

  8. #8
    150+ Forum Groupie luisgordo's Avatar
    Join Date
    Jan 2007
    Location
    Houston, TX
    Posts
    275
    Contribute If you enjoy reading the
    content here, click the below
    image to support MyCockpit site.
    Click Here To Contribute To Our Site

    Just found this link searching something else, and thought it might be useful:
    http://en.wikipedia.org/wiki/Switch
    Luis Gordo
    Instructor StationTM - www.iStationGordo.com

  9. Thanks W9XE/Project777, Matt Olieman thanked for this post

Similar Threads

  1. Wiring a DPDT, Center ON switch
    By capetonian in forum Westozy's Mechanical Engineering
    Replies: 4
    Last Post: 12-03-2009, 05:37 PM
  2. DPDT switch interfacing visual guide for Learjet 45
    By Tomlin in forum I/O Interfacing Hardware and Software
    Replies: 0
    Last Post: 08-09-2007, 10:42 AM