Electronics (alt.electronics)

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JSW
 
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Default Current sensing, I think??????

Hi
I want to be able to connect smoke alarms to my existing house alarm. At my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery and
allows the smoke alarm to be connected to the main alarm. This pcb probably
has a voltage regulator on it (12v to 9v) and some sort of current sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John


  #2   Report Post  
Fred Bloggs
 
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Default Current sensing, I think??????



JSW wrote:
Hi
I want to be able to connect smoke alarms to my existing house alarm. At my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery and
allows the smoke alarm to be connected to the main alarm. This pcb probably
has a voltage regulator on it (12v to 9v) and some sort of current sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to much
for it and a want a few of them, does anybody know a circuit for such a
thing?


Yeah- it's called a relay. Your house alarm has inputs labeled N.O. and
N.C.- so you run a wire pair from one of those over to relay contacts
inside smoke alarm. Your difficulty arises on adapting the existing
smoke alarm circuitry to activate the relay. This will be over your
head- so go buy the finished product or drop the idea entirely.


  #3   Report Post  
Frank Raffaeli
 
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Default Current sensing, I think??????

"JSW" wrote in message ...
Hi
I want to be able to connect smoke alarms to my existing house alarm. At my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery and
allows the smoke alarm to be connected to the main alarm. This pcb probably
has a voltage regulator on it (12v to 9v) and some sort of current sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John


It's a cleaver idea. The sonalert / transducer inside the remote alarm
will draw enough current to distiguish between alarm and quiescent.
Try this:

From Central Control: +12V, Sense, Return (Gnd)
Use a 3-terminal Vreg to supply remote detector.
_________
+12V ----+-----/\/\/----+-----| In |---9V
\ R1=? | | Out |
| | |________| To

Q1 PNP |----/\/\/---+ | Det
/| R2=1K |
| +-------Gnd
Sense --+ |
| |
/ |
\ R3 = 10K - 22K |
/ |
| |
Gnd ----+------------------------+

Adjust R1 to sense the current. The PNP transistor's conduction is
temperature and input dependent. Also, R1 cannot be so large that the
drop between the 12V input and the regulator exceeds the regulator
lead voltage. You may need additional circuitry between the sense line
and the alarm activation circuit. The sense line is pulled to the Vreg
input voltage when enough current flows in R1. You may also require
some noise filtering, like a cap between E-B of Q1.

Frank Raffaeli
http://www.aomwireless.com/
  #4   Report Post  
scada
 
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Default Current sensing, I think??????


"JSW" wrote in message
...
Hi
I want to be able to connect smoke alarms to my existing house alarm. At

my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery

and
allows the smoke alarm to be connected to the main alarm. This pcb

probably
has a voltage regulator on it (12v to 9v) and some sort of current sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to

much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John



These factory smoke alarms are tested for Heat, Smoke, and whatever adverse
conditions occur during a fire! Do you realy want to take that chance that
you may get it all right!!!! Buying a proven unit gives peace of mind!


  #5   Report Post  
Edward
 
Posts: n/a
Default Current sensing, I think??????

"scada" wrote in message
.net...

"JSW" wrote in message
...
Hi
I want to be able to connect smoke alarms to my existing house alarm. At

my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery

and
allows the smoke alarm to be connected to the main alarm. This pcb

probably
has a voltage regulator on it (12v to 9v) and some sort of current

sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to

much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John



These factory smoke alarms are tested for Heat, Smoke, and whatever

adverse
conditions occur during a fire! Do you realy want to take that chance that
you may get it all right!!!! Buying a proven unit gives peace of mind!



You should also check that your insurance is still valid if you "modify"
your alarm system.





  #6   Report Post  
Fred Bloggs
 
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Default Current sensing, I think??????



tim kettring wrote:
Or you can just buy the right smokes from alarm shops , be sure to
order 1 " terminator " unit ( i think it is called for each ) ( they
alert the alarm box that a wire has been cut ) , that is on most
professional alarm boxes ( like the Z-900 etc..by aritech corp )
...thats 12v 0v AND 6v sensing too , probably not on most
non-professional alarm boxes .

Tim , CET , previous alarm installer for 1 year .


Right- and there are models that run off 120VAC with battery backup, and
they are alarmed as well as alarm- meaning central alarm control can
cause smoke alarm to sound via NO or NC inputs- as well as other way
around. Generally you want latched operation requiring manual reset-
making that transistor thing inadequate.

  #7   Report Post  
Terry
 
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Default Current sensing, I think??????

Edward wrote:

"scada" wrote in message
.net...

"JSW" wrote in message
...
Hi
I want to be able to connect smoke alarms to my existing house alarm. At

my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery

and
allows the smoke alarm to be connected to the main alarm. This pcb

probably
has a voltage regulator on it (12v to 9v) and some sort of current

sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to

much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John



These factory smoke alarms are tested for Heat, Smoke, and whatever

adverse
conditions occur during a fire! Do you realy want to take that chance that
you may get it all right!!!! Buying a proven unit gives peace of mind!



You should also check that your insurance is still valid if you "modify"
your alarm system.


It's a good idea: But suppose it misoperates, perhaps due to some
voltage glitch in the powers supply? Could a 'non standard'
modification that caused a 'false alarm' to the company
monitoring your home alarm system then cost you for a 'false
call-out'.
On other hand if your house is of average size and you are NOT
connected to an alarm monitoring company you can probably hear
your individual smoke alarms if they go off anywhere in the
house? We can.
Here; for rented accommodation there are some requirements that
the alarm be a) AC powered; so kids don't steal the batteries for
their 'toys' and b) With more than one habitable floor, alarms be
linked between floors.
Personally I would keep your systems separate with the possible
exception of an intermediate relay.
Relays are very good at physically/electrically separating
different systems.
Then if a smoke alarm works to activate the home alarm system,
fine. If it doesn't you still got your smoke alarm/s standing
alone, not depending on anything else to power them or give the
alert! Change smoke alarm batteries yearly. Also most smoke
alarms will give a 'beep' indication if battery goes low.
If any gas operated appliances (vented or not) also use a CO
(Carbon Monoxide) detector. Could be cheapest life insurance you
buy!
Last year, near here, someone had a night time fire in their AC
main fuse panel. ALL POWER went off; no lights no AC operated
smoke alarms, nothing. They were lucky to get out!
  #8   Report Post  
Gel
 
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Default Current sensing, I think??????

In the Uk both BRK & Firex sell these
conversion boards themselves, so one can assume they're kosher.


Terry wrote in message ...
Edward wrote:

"scada" wrote in message
.net...

"JSW" wrote in message
...
Hi
I want to be able to connect smoke alarms to my existing house alarm. At

my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery

and
allows the smoke alarm to be connected to the main alarm. This pcb

probably
has a voltage regulator on it (12v to 9v) and some sort of current

sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to

much
for it and a want a few of them, does anybody know a circuit for such a
thing?

Cheers
John



These factory smoke alarms are tested for Heat, Smoke, and whatever

adverse
conditions occur during a fire! Do you realy want to take that chance that
you may get it all right!!!! Buying a proven unit gives peace of mind!



You should also check that your insurance is still valid if you "modify"
your alarm system.


It's a good idea: But suppose it misoperates, perhaps due to some
voltage glitch in the powers supply? Could a 'non standard'
modification that caused a 'false alarm' to the company
monitoring your home alarm system then cost you for a 'false
call-out'.
On other hand if your house is of average size and you are NOT
connected to an alarm monitoring company you can probably hear
your individual smoke alarms if they go off anywhere in the
house? We can.
Here; for rented accommodation there are some requirements that
the alarm be a) AC powered; so kids don't steal the batteries for
their 'toys' and b) With more than one habitable floor, alarms be
linked between floors.
Personally I would keep your systems separate with the possible
exception of an intermediate relay.
Relays are very good at physically/electrically separating
different systems.
Then if a smoke alarm works to activate the home alarm system,
fine. If it doesn't you still got your smoke alarm/s standing
alone, not depending on anything else to power them or give the
alert! Change smoke alarm batteries yearly. Also most smoke
alarms will give a 'beep' indication if battery goes low.
If any gas operated appliances (vented or not) also use a CO
(Carbon Monoxide) detector. Could be cheapest life insurance you
buy!
Last year, near here, someone had a night time fire in their AC
main fuse panel. ALL POWER went off; no lights no AC operated
smoke alarms, nothing. They were lucky to get out!

  #9   Report Post  
Roy J.P. Quijano
 
Posts: n/a
Default Current sensing, I think??????

It's not that easy, then again t's not terribly difficlut, but it's more
than getting it down in numbers and then parts, you need to etch out the
circuit boards and you must have a template or the least a simple
circuit board to mimic, maybe you should buy One Unit and make the rest
yourself and hope it comes out cheaper.

about ten years ago I made a ac/dc power supply circuit to supply for a
nice portable tv an uncle had given me, the original had cracked and I
just fancied a new oe after repeated jumper and glue tricks, so I got a
PCB Kit from Circuit Masters & etched it out in my mini backyard shop,
the iodine solution stunk a bit, but I was lucky I only had to mimic
some fairly simple tracks and transfer all the components to it, you
will need to get all the components the mfgr uses on that model ( they
may or may not be exclusive or available) if you don't find a more
feasible model in a good Electronics Circuit Cook Book.

good luck, if you're into your security system you'll enjoy it

  #10   Report Post  
Roy J.P. Quijano
 
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Default PCB Kits Correction

well I trust you have found r decided how you are going to approach your
sensing needs.

NOTE The Kit i used was from " Circuit Specialist " not, Masters as
In my replied.

in those days there was no internet opytion, but they are there now as
well., happy etching, i may purchase another kit just to have it around
you never know when it can come in handy again.


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