3 terminal micro switch help!

Discussion in 'The Projects Forum' started by judoGTI, Jan 5, 2010.

  1. judoGTI

    Thread Starter Member

    May 26, 2005
    Hey guys -

    Im back and working on a new project! Im building on of the most useless machines ever! (http://www.instructables.com/id/The-Most-Useless-Machine/)

    I went to my surplus electronics dealer and purchased two 3-terminal microswitches (bought 2 just in case one didnt work). Im trying to test each part individually before I wire the circuit together. Im having a bit of trouble with the micro switches however.

    Ive attached an image of what I have setup with my power supply and breadboard, however the when the 3 terminal micro switch is in the mix, it simply doesnt work. Do I need to have all 3 terminals wired to get the switch to work? I was hoping the the terminal would work with just 2 terms. wire up (being in either on or off mode and the button switching it).

    Thanks for any tips!
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Look at the microswitch closely. The terminals might be marked NO - NC - COM. If that is the case, the COM terminal is connected to the NC terminal with the plunger up. When the plunger is depressed, the COM terminal contacts the NO terminal.

    Or you can use a meter to determine that information.
  3. SgtWookie


    Jul 17, 2007
    Much of the time, the center terminal on the switch is the common terminal.
  4. judoGTI

    Thread Starter Member

    May 26, 2005
    Thanks for the replies. It was a noob mistake with my breadboard, I had the power going down one 'row' of holes when in fact they were 'connected' in the other/perpendicular direction (I hope that makes sense). Moved one of the wires and all was well. :)