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how much current 9v smoke detector?

N

newsdude

Jan 1, 1970
0
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.
 
P

Phil Allison

Jan 1, 1970
0
** Groper alert !

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


** Maybe about 25,000.

Average drain is about 40 uA.

More when the alarm goes off though.

and what kind of resistor(s) to reduce the voltage a bit or
will
9v detectors take 12v ok.


** Probably.

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



....... Phil
 
J

John Fields

Jan 1, 1970
0
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.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
newsdude said:
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.

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.
 
P

PeterD

Jan 1, 1970
0
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.

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!
 
H

Homer J Simpson

Jan 1, 1970
0
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.

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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