SPDT Momentary Selection

Discussion in 'General Electronics Chat' started by _Anthony_, Mar 16, 2013.

  1. _Anthony_

    Thread Starter Member

    Mar 16, 2013
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    I am looking to debounce a momentary pushbutton. I have decided on an SPDT momentary switch with NAND gates. However I am having trouble in selecting the SPDT switch.

    It seems as though it should be simple: 3 poles with common, open and closed. However when I look at the switch datasheets they are not like that.

    The CK switch NP8 series looks about right. But it has 4 poles, and comes in 3 and 4 wire versions. I don't follow what the 4th pole is for, or the 4 wire version.

    If I look at the ATEM IP series, then most are shown with only 2 pins. The ones described as NO look like normal SPST switches, and the ones described as NO/NC look like DPST!

    So can anyone suggest which of these would be right for my debouncing circuit?

    Thanks,
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Can you provide part numbers?
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    SPDT is what you want.

    Something "described as NO/NC look like DPST" would fit this bill.
     
  4. tubeguy

    Well-Known Member

    Nov 3, 2012
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  5. _Anthony_

    Thread Starter Member

    Mar 16, 2013
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    Thanks for the quick replies.

    The one I have is the NP Series NP8S2R202GE. The data sheet is here: www.ck-components.com/66840/np_15jan13.pdf/
    The schematic on page A124 shows what looks like two options: either a shared common or separate Open/Closed. I assume that means it can be wired up either way. If I wanted the flying lead version then I assume the 3-wire gives me the shared common.

    Another one I looked at is the APEM IP Series: http://www.apem.com/files/apem/brochures/switch-pushbutton-IP-mom-ENG.pdf
    On page B1-20 it also has two options: either NO or NO/NC. In this case the NO has only two lugs. I assume I would need the IPR5SAD to get a shared common.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    You can use that 4-pin C&K NP8 switch as shown in the circuit below:

    [​IMG]
    You can choose either 7400 TTL or 4011 CMOS NAND gates depending on the rest of your design.
     
  7. _Anthony_

    Thread Starter Member

    Mar 16, 2013
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    That's excellent, thanks very much. That's exactly what I was hoping to confirm.
     
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