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how much current 9v smoke detector?

Discussion in 'Electronic Design' started by newsdude, Feb 27, 2007.

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  1. newsdude

    newsdude Guest

    I want to hardwire some 9v smoke detectors to a wall transformer
    and was wondering how my detectors i could run from a 12v / 1500mA
    supply and what kind of resistor(s) to reduce the voltage a bit or
    will
    9v detectors take 12v ok.
     
  2. Phil Allison

    Phil Allison Guest

    ** Groper alert !


    ** Maybe about 25,000.

    Average drain is about 40 uA.

    More when the alarm goes off though.


    ** Probably.

    But use a resistor and 9.1 volt zener to be safe.



    ....... Phil
     
  3. John Fields

    John Fields Guest

     
  4. Maybe. Maybe not. If you want your smoke detector(s) to meet code, you
    may need to provide a backup power source. Mine use 9V batteries for
    backup. In addition, they may require some means of alerting the
    homeowner when the backup supply is depleted.
     
  5. PeterD

    PeterD Guest

    Realize the current drain is non-constant, but is pulsed. That is the
    smoke detector sleeps about 99% of the time, and wakes up about 1% of
    the time. The current drain changes with the detector's mode. Also the
    current drain is *much* higher when in alarm mode.

    If you want this to be safe you really should use detectors that are
    meant to be used either on line voltages, or hardwired to alarm
    systems, instead of kludging your own.

    but if you must, I'd suggest a 9 volt regulator on the output of the
    12volt wall wart would do the trick. You should also have a backup
    battery configured, which negates whatever advantage that the AC power
    might give you (are you trying to avoid changing batteries?)

    After all, many fires cause a loss of AC power (especially those that
    are electrical in origin) and that is not the time when you want your
    smoke detectors to go off-line!
     
  6. Don't. You are tinkering with your fire insurance policy. Buy AC powered
    units and keep the battery units as well.


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