Voltage drop switching relays?

[Joe in Bendigo]

Hi,
I need a design or some design help to build a circuit for security systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series and
have normally closed relays inside them. When one of them is triggered, the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.

 

[Phil Allison]

"Joe in Bendigo" <jhovel@-spam-gmx.net>

The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the security
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....

We really need to know which room the alarm came from - see the dilemma?

** Dear Joe,

instead of wasting you time chasing stray cats and strange sources of IR
energy why not SOLVE the silly problem ???

Replace those *PITA* PIR sensors with dual sensor IR / microwave ones.
These will only trip the alarm when BOTH sensors indicate there is cause to
do so at the same time. All the usual sources of false alarms ( moths, cats,
rats, passing car headlights, swinging doors or curtains in the wind etc )
will trip only one or the other type of sensor - but not both.

If you can find some microwave sensor types available cheaply - then use
them wired in parallel with the PIR ones. Locate them covering the same
space and *voila*.




............ Phil

 

[John Crighton]

On Thu, 27 May 2004 11:57:55 GMT, "Joe in Bendigo"
<jhovel@-spam-gmx.net> wrote:

Hi,
I need a design or some design help to build a circuit for security systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series and
have normally closed relays inside them. When one of them is triggered, the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.


Hello Joe,

since you have asked for any ideas, how about
an opto coupler across each closed relay contacts.

If a closed relay contact opens, the opto operates and
causes a small separately powered circuit to unlatch (delatch)
or a small separately powerd relay to unlatch itself.
A little led would show that the latch had been released.

That would be six little modules each powerd with its own
9V battery or whatever and two little push buttons on each
module to set or reset the latch the next day.
A bit of food for thought.

Regards,
John Crighton
Sydney

 

[logized]

"Joe in Bendigo" <jhovel@-spam-gmx.net> wrote in message
news:7Jktc.13339$L.1654@news-server.bigpond.net.au...

Hi,
I need a design or some design help to build a circuit for security
systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of
the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.


Joe,

You could try using a Microchip PIC 16F628 microcontroller
http://ww1.microchip.com/downloads/en/DeviceDoc/40300c.pdf - these are cheap
and have voltage comparators, could be programmed to activate relays etc as
required.
An alternative way to detect which sensor was triggered, would be to modify
each relay circuit so that the relay operates for a different amount of time
when triggered (by experimenting with changing capacitors in the relay
circuit for example).
You could then use the PIC microcontroller to measure the relay operate time
to determine which sensor was triggered.

Dave

 

[scada]

"Joe in Bendigo" <jhovel@-spam-gmx.net> wrote in message
news:7Jktc.13339$L.1654@news-server.bigpond.net.au...

Hi,
I need a design or some design help to build a circuit for security
systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of
the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.

Using different resistors to pull different Relay voltage coils could be a
problem. The relay pick up currents will be higher than the holding
currents, which would make it hard to define different voltage levels. Use
your resistor idea, but input that to an Analog to Digital converter then
input that to the serial port of a PC and have a program do data logging.

 

[Ken Taylor]

"scada" <scada@optonline.net> wrote in message
news:QSstc.60227$cz5.24909271@news4.srv.hcvlny.cv.net...

"Joe in Bendigo" <jhovel@-spam-gmx.net> wrote in message
news:7Jktc.13339$L.1654@news-server.bigpond.net.au...
Hi,
I need a design or some design help to build a circuit for security
systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit, which then dials out on
a
phone line to a control room who sends someone out to find the cause of
the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that
there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's
thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but
isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage
dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.



Using different resistors to pull different Relay voltage coils could be a
problem. The relay pick up currents will be higher than the holding
currents, which would make it hard to define different voltage levels. Use
your resistor idea, but input that to an Analog to Digital converter then
input that to the serial port of a PC and have a program do data logging.


The OP is referring to putting resistors in the relay change-over terminal

connections, not in series with the coil. While a comparator would probably
work, the false triggering would continue, as Phil has pointed out. The
system is a bodge and should be replaced - that would almost certainly be
less than the cost of continued call-outs.

Ken

 

[Bushy]

G'day Mate,

A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit,

So modify the circuit to only trigger on two pulses repeated within a
certain time. The sensor will trigger several times on most people, while
the cat won't set them of anywhere near as often.

which then dials out on a
phone line to a control room who sends someone out to find the cause of
the
alarm.

Maybe set to re-ring every time it is triggered and the common ones would
then require two calls to trigger a callout. Sort of like train the operator
to be a computer program. Each call is only a few cents! As long as you
don't give the Kiwi operators more than half an hour for lunch, 'cause it
takes to long to retrain them!

The problem is that these sensors are only on at night,

Easy, put a bit of black insulation tape over the light sensor and they will
work as happily in the daylight!

and are in a
different room each.

How much do you want to spend???

A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Are you sure, is there another way round like add a couple of cheap
black/white radio or cable cameras and switch between them?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.

A couple of local cameras and a vcr, or a cheap old 486 laptop, a modem, a
powerpoint(?) and a webcam to work out which sites have cats and which ones
don't? You can pick up a 486 for a couple of sixpacks, and a cheap webcam
from Kerri-Anne http://sites.ninemsn.com.au/minisite/Mornings/default.asp
you can even get the second one for halfprice, but you could go to your
local retail outlet and work out a bargain on last weeks model they are
stuck with..........

Or the cheap way, a cat trap?

So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?

You can use two voltage comparator circuits at each relay to compare the
voltages at each point. Should find a circuit in the 741 op amp cookbook!

Hope this helps,
Peter

Your help would be very much appreciated!

I knew it would be, and it gives really nice fuzzy glow, oops, how many
drugs have I had?

Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.

 

On Thu, 27 May 2004 13:53:01 GMT, john_c@tpg.com.au (John Crighton)
wrote:

since you have asked for any ideas, how about
an opto coupler across each closed relay contacts.

If a closed relay contact opens, the opto operates and
causes a small separately powered circuit to unlatch (delatch)
or a small separately powerd relay to unlatch itself.
A little led would show that the latch had been released.

That would be six little modules each powerd with its own
9V battery or whatever and two little push buttons on each
module to set or reset the latch the next day.
A bit of food for thought.

Stole my idea, only I would use the 12Vdc supply at sensor.
Trigger two relays, one acts to activate the alarm, the other is wired
as a hold in relay to illuminate an LED.

It falls short as:
Most sensors are on 24/7 which means as soon as somone walks in the
room at any time of the day and the led would latch.

Wire the system so that there is only power when the system is armed
wont work either as the tech normally has to disarm to inspect the
sensors, and as soon as he/she enters the room to inspect each sensor
it would trigger.

 

[John Crighton]

On Sat, 29 May 2004 18:27:16 +1000, David Sauer wrote:

On Thu, 27 May 2004 13:53:01 GMT, john_c@tpg.com.au (John Crighton)
wrote:

since you have asked for any ideas, how about
an opto coupler across each closed relay contacts.

If a closed relay contact opens, the opto operates and
causes a small separately powered circuit to unlatch (delatch)
or a small separately powerd relay to unlatch itself.
A little led would show that the latch had been released.

That would be six little modules each powerd with its own
9V battery or whatever and two little push buttons on each
module to set or reset the latch the next day.
A bit of food for thought.

Stole my idea, only I would use the 12Vdc supply at sensor.
Trigger two relays, one acts to activate the alarm, the other is wired
as a hold in relay to illuminate an LED.

It falls short as:
Most sensors are on 24/7 which means as soon as somone walks in the
room at any time of the day and the led would latch.

Wire the system so that there is only power when the system is armed
wont work either as the tech normally has to disarm to inspect the
sensors, and as soon as he/she enters the room to inspect each sensor
it would trigger.

From discount shops and two dollars shops you can
buy little battery operated clocks. The type with hands.
If one of those cheap $2 clocks had its battery power
removed by a transistor switch, when the latch was
released by the cat or curtains moving. The time at
which that event happened during the night will be
indicated by the stopped clock.

Yes you are correct as soon as someone entered the
room the clock would stop.

Now you are going to say "How does the guy get out
of the room without moving when he sets the latch?"
A little timer(555) set for a minute or two would do, to
inhibit the opto coupler to allow him to exit the room.

Phill has hit the nail on the head with the use of
two different sensors to avoid false triggering.
That is a better fix than determining when the
false triggering occurred.

Regards,
John Crighton
Hornsby

 

[Ian Smith]

I hope you're making a lot of money, cos you seem to know a lot of
shit.







.................................................................
Posted via TITANnews - Uncensored Newsgroups Access

at http://www.TitanNews.com
-=Every Newsgroup - Anonymous, UNCENSORED, BROADBAND Downloads=-

 

[Soeren]

Hi Joe,

What I need is a way of triggering a separate relay for each voltage
dorp value (or a small range either way), so that I can record the
events in each room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?

Take a look at the LM3914 LED voltmeter (LEDs could be replaced with opto
couplers or perhaps drive reed relays directly.


--
Regards,
Soeren

* If it puzzles you dear... Reverse engineer *
New forum: <URL:http://www.ElektronikTeknolog.dk/cgi-bin/SPEED/>

 

[Joe in Bendigo]

Thank you all for your input!
Some of your advice has made me rethink the issues and others I have
followed up by reading the sources you suggested.
This suggestion of using an LED voltmeter appears the most easily managed,
since I'm clearly no electronics expert.
I may even drive tone generators from the LED outputs instead and plug their
outpu into the microphone input of a laptop and record any triggers onto
file - so we can visually see where the trips occur and how often.
Cheers!
Joe

"Soeren" <Look@iNO-SPAMt.dk> wrote in message
news:Xns94F9F1E45A525oo8ooLooK4iToo8oo@62.243.74.163...

Hi Joe,


What I need is a way of triggering a separate relay for each voltage
dorp value (or a small range either way), so that I can record the
events in each room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?

Take a look at the LM3914 LED voltmeter (LEDs could be replaced with opto
couplers or perhaps drive reed relays directly.


--
Regards,
Soeren

* If it puzzles you dear... Reverse engineer *
New forum: <URL:http://www.ElektronikTeknolog.dk/cgi-bin/SPEED/

 

[Phil Allison]

"Joe in Bendigo" <jhovel@-spam-gmx.net>

Thank you all for your input!
Some of your advice has made me rethink the issues and others I have
followed up by reading the sources you suggested.
This suggestion of using an LED voltmeter appears the most easily managed,
since I'm clearly no electronics expert.
I may even drive tone generators from the LED outputs instead and plug
their
outpu into the microphone input of a laptop and record any triggers onto
file - so we can visually see where the trips occur and how often.
Cheers!
Joe

** Oh dear, so our Joe is determined to go to great lengths to solid
evidence on that poor damn cat !!

Meeooooooowwwww.......





............. Phil

 

[Joe in Bendigo]

Dear Phil,
I read your message with particular interest, since it solves the problem
properly.
However, you miss the point: I HAVE to find what causes these hits before I
do anything! I CAN'T rewire the buildings, nor change the sensor types, nor
the panels. These issues are all controlled by the design branch of the
education department. Most of these old buildings have asbestos in the
ceilings and need specialist intervention to rewire anything ($100,000s).
The only authorisation I have is to "fix the sensor problem". Even changing
from ultrasonic sensors to PIR takes a paper war - as we can't source the
original type U/S any more.....
In some cases the PIRs are at fault, but often the environment, in which
case we can make recommendation to change their location or type - that's
it.
I know this is a work around, but working around I have to do....

Cheers,
Joe

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2i08pvFhjqhmU1@uni-berlin.de...

"Joe in Bendigo" <jhovel@-spam-gmx.net

Thank you all for your input!
Some of your advice has made me rethink the issues and others I have
followed up by reading the sources you suggested.
This suggestion of using an LED voltmeter appears the most easily
managed,
since I'm clearly no electronics expert.
I may even drive tone generators from the LED outputs instead and plug
their
outpu into the microphone input of a laptop and record any triggers onto
file - so we can visually see where the trips occur and how often.
Cheers!
Joe



** Oh dear, so our Joe is determined to go to great lengths to solid
evidence on that poor damn cat !!

Meeooooooowwwww.......





............ Phil

 

[Phil Allison]

"Joe in Bendigo" <jhovel@-spam-gmx.net

Dear Phil,

I read your message with particular interest, since it solves the problem
properly.

** Now he tells me !

However, you miss the point:

** Which Joe did not previously post.

I HAVE to find what causes these hits before I
do anything!

** May easily be one faulty sensor - you have to make substitutions to
ever find that !!

I CAN'T rewire the buildings, nor change the sensor types, nor
the panels.

** Then go do something else - the alarm problem is not yours to solve.

These issues are all controlled by the design branch of the
education department. Most of these old buildings have asbestos in the
ceilings and need specialist intervention to rewire anything ($100,000s).

** That is a straw man - replacing sensors needs no new wiring.

The only authorisation I have is to "fix the sensor problem".

** Then you have no real authorisation - since (you say) you cannot
change anything.

Even changing> from ultrasonic sensors to PIR takes a paper war - as we
can't source the
original type U/S any more.....

** Dual type sensors are cheap and any brand will do.

In some cases the PIRs are at fault, but often the environment, in which
case we can make recommendation to change their location or type - that's
it.

** Then do just that and nothing else till approval comes through.

I know this is a work around, but working around I have to do....

** Maybe you could put a dog with a loud bark in each room ???




............... Phil

 

[Joe in Bendigo]

Joe

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2i4qtfFja9sfU1@uni-berlin.de...

"Joe in Bendigo" <jhovel@-spam-gmx.net
Dear Phil,

I read your message with particular interest, since it solves the
problem
properly.


** Now he tells me !


However, you miss the point:


** Which Joe did not previously post.


I HAVE to find what causes these hits before I
do anything!


** May easily be one faulty sensor - you have to make substitutions to
ever find that !!


I CAN'T rewire the buildings, nor change the sensor types, nor
the panels.


** Then go do something else - the alarm problem is not yours to solve.



These issues are all controlled by the design branch of the
education department. Most of these old buildings have asbestos in the
ceilings and need specialist intervention to rewire anything
($100,000s).


** That is a straw man - replacing sensors needs no new wiring.


The only authorisation I have is to "fix the sensor problem".


** Then you have no real authorisation - since (you say) you cannot
change anything.


Even changing> from ultrasonic sensors to PIR takes a paper war - as we
can't source the
original type U/S any more.....


** Dual type sensors are cheap and any brand will do.


In some cases the PIRs are at fault, but often the environment, in which
case we can make recommendation to change their location or type -
that's
it.


** Then do just that and nothing else till approval comes through.


I know this is a work around, but working around I have to do....



** Maybe you could put a dog with a loud bark in each room ???




.............. Phil

 

[Kirk Shirley]

Joe in Bendigo <jhovel@-spam-gmx.net> wrote in message
news:7Jktc.13339$L.1654@news-server.bigpond.net.au...

Hi,
I need a design or some design help to build a circuit for security
systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of
the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.


Dear Joe,

I agree with an earlier post of replacing them. If you don't want to do
this the simplest circuit is to use some "tattle-tales" used in Air
Conditioning. These are just some very low current fuses that open when your
relay contacts open..
Kirk

 

[Larry]

"Kirk Shirley" <none@hotmail.com> wrote in message news:<btCdnfILfe7s8FfdRVn-sA@comcast.com>...

Joe in Bendigo <jhovel@-spam-gmx.net> wrote in message
news:7Jktc.13339$L.1654@news-server.bigpond.net.au...
Hi,
I need a design or some design help to build a circuit for security
systems
fault finding.
First a little explanation:
A number (up to 6) of PIR (passive infrared) sensor are wired in series
and
have normally closed relays inside them. When one of them is triggered,
the
contacts open, setting an alarm for the circuit, which then dials out on a
phone line to a control room who sends someone out to find the cause of
the
alarm.
The problem is that these sensors are only on at night, and are in a
different room each. A common fault for me to have reported is that there
were frequent "single hits" (short infrared events that triggered one of
the
PIRs) in a circuit and the the circuit was isolated to stop the secuirty
guard driving to the site lots of times without ever finding anything.
Occasionally it is a heater that was left on overnight and it's thermostat
has been cycling. Other times we suspect a cat roaming buildings at
night....
We really need to know which room the alarm came from - see the dilemma?

Now, rewiring each sensor separately would be current proactice, but isn't
an option for various reasons.
I can put a resitor across the relay terminals in each sensor without
compromising its effectiveness. I thought that if I put a DIFFERENT
resistor
across each sensor, then when one is triggered, I would get a SPECIFIC
voltage drop (for EACH sensor) in the circuit!
What I need is a way of triggering a separate relay for each voltage dorp
value (or a small range either way), so that I can record the events in
each
room to try and determine the cause.
So I need a circuit which latches or opens a relay for each of a small
range
of 6 voltges: eg. 3V to 3.5V - 4V to 4.5V - 5V-5.5V etc.
Anyone have any ideas?
Your help would be very much appreciated!
Cheers,
Joe in Australia
-----
remove -spam- form e-mail to contact me directly.


Dear Joe,
I agree with an earlier post of replacing them. If you don't want to do
this the simplest circuit is to use some "tattle-tales" used in Air
Conditioning. These are just some very low current fuses that open when your
relay contacts open..
Kirk

Kirk's idea will work, I've heard of people useing flash bulbs across
NC contacts.
What I used years ago goes this way.
Your PIRs are powered by 12V or 24V, on each suspect PIR use a small SCR
1/2 anp or so a small lamp or LED and a resistor or two for the gateing
this way you can trace your mystery.
Hope it helps