Dry contacts?

Discussion in 'General Electronics Chat' started by susannah, May 3, 2014.

  1. susannah

    Thread Starter Active Member

    Feb 14, 2010
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    0
    Our neighbor has security camera which has "dry contact control" pins for zoom, focus, menu and com.

    If we put 12V to let say zoom pin, then does it zoom? Or what this means?
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    3,360
    My guess is that it means that a simple switch closure across two terminals is all that is required in order to perform the stated function. No voltage must be applied to the terminals.
     
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  3. susannah

    Thread Starter Active Member

    Feb 14, 2010
    87
    0
    Thanks.

    These dry contacts are under "Controller" text in picture. If i want to zoom, what i connect where?

    Here is picture:
    [​IMG]
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,432
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    What does the instruction manual say?
    What is the make and model of the security camera?

    Edit: Connect a NO (Normally Open) push button switch between Z and C to zoom.
     
  5. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    One definition of, "dry contact" is that very little current flows through them. The last one I saw was limited to .01 amps. They are gold plated so they will make contact with almost no voltage to pierce through an unfortunate oxide layer. If you exceed the current rating, the gold will disappear and the contacts will start failing to connect properly.

    The moral of the story is, do not apply current from your own source. Just make the connection.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    It generally means a contact that does not control the main current of the relevant circuit, IOW, it is used to control the primary operator in an auxiliary fashion.
    In this case it could be the low level input to the drive or whatever the means of driving the zoom motor or operator is.
    Max.
     
  7. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,143
    202
    Dry means contacts that are potential free. e.g. A simple switch
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
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    There is always a potential, it usually means that the current carried is inconsequential or insignificant.
    Max.
     
  9. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    OK, free from any externally applied potential.

    I don;t go along with insignificant current ratings.

    http://www.google.com/url?sa=t&rct=...f_RaDiKFK_BP3Jw&bvm=bv.65788261,d.cWc&cad=rja

    Dry contacts can be inputs to outputs. The ones referenced above are rated at 2 Amps, Hardly insignificant.

    I did a fair amount of fire alarm interfacing with hydrogen and toxic gas alarms and the design of my own panels that communicated with dry contacts. My external "dry contact" would complete the circuit to a 24 VAC relay.

    For my sanity and electrical safety, all communication was with dry contacts unless the box' responsibility directly controlled something like a siren or valve. A light in a panel in another room had to be powered by the room enclosure. I could not give the "impression" that the panel was operational.
     
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