How motion sensors work

On 2/23/2010 5:56 AM Jim Yanik spake thus:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:4B830EC4.3030304@electrooptical.net:

On 2/21/2010 8:41 PM, David Nebenzahl wrote:

On 2/21/2010 4:12 PM David Nebenzahl spake thus:

I'd like to get responses, ideally, from folks who actually know how
these things work, and not the usual Usenet speculation.

I install a lot of motion-detector lights for clients. A lot of these
installations are problematic. I just adjusted one for the third or
fourth time because the light was staying on all the time, even though
the sensor unit (I replaced the entire unit with a Heath-Zenity sensor
recently) was working properly.

It might help for me to know how, exactly, these sensors work. By
"sensors" I mean the actual sensor, as well asw the entire unit with
the support electronics.

So I found this circuit out there in the wild:

http://www.freeinfosociety.com/electronics/schemview.php?id=2074

It uses something called a PIR. Does that stand for piezoelectric
infrared? I've seen other references to piezo sensors: how do those
work? Do they both send and receive a signal? (The device shown here is
a 3-terminal thingie.)

Close--pyroelectric, and all pyroelectrics are also piezoelectric,
afaik.

NOPE. PIR=Passive Infra-Red.
Click to expand...
Nope.

They can be called that, but they are also called pyroelectric (look it
up if you don't believe me). And no, I don't think they have anything to
do with piezoelectricity; they are, after all, passive elements.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"
 
They can be called that, but they are also called pyroelectric
(look it up if you don't believe me). And no, I don't think they
have anything to do with piezoelectricity; they are, after all,
passive elements.
Click to expand...
The motion-sensor device is /passive/, but the /element/ isn't. "Passive"
has two meanings here, with respect to the context.

I don't know what materials are currently used, but it is a /fact/ that
motion sensors originally used piezoelectric plastics.
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm16p8$flf$1@news.eternal-september.org:

They can be called that, but they are also called pyroelectric
(look it up if you don't believe me). And no, I don't think they
have anything to do with piezoelectricity; they are, after all,
passive elements.

The motion-sensor device is /passive/, but the /element/ isn't. "Passive"
has two meanings here, with respect to the context.

I don't know what materials are currently used, but it is a /fact/ that
motion sensors originally used piezoelectric plastics.
Click to expand...
in terms of -sensing-,"passive" means that no radiation is emitted;
the sensor depends on existing,external reflected radiation.
Unlike say a microwave sensor that emits a signal and detects it's
reflection.

Naturally,the sensor itself is going to generate an output signal.
(from -some- source of stimulation...)

--
Jim Yanik
jyanik
at
localnet
dot com
 
On 2/23/2010 8:56 AM, Jim Yanik wrote:
Phil Hobbs<pcdhSpamMeSenseless@electrooptical.net> wrote in
news:4B830EC4.3030304@electrooptical.net:

On 2/21/2010 8:41 PM, David Nebenzahl wrote:
On 2/21/2010 4:12 PM David Nebenzahl spake thus:

I'd like to get responses, ideally, from folks who actually know how
these things work, and not the usual Usenet speculation.

I install a lot of motion-detector lights for clients. A lot of these
installations are problematic. I just adjusted one for the third or
fourth time because the light was staying on all the time, even though
the sensor unit (I replaced the entire unit with a Heath-Zenity sensor
recently) was working properly.

It might help for me to know how, exactly, these sensors work. By
"sensors" I mean the actual sensor, as well asw the entire unit with
the support electronics.

So I found this circuit out there in the wild:

http://www.freeinfosociety.com/electronics/schemview.php?id=2074

It uses something called a PIR. Does that stand for piezoelectric
infrared? I've seen other references to piezo sensors: how do those
work? Do they both send and receive a signal? (The device shown here is
a 3-terminal thingie.)


Close--pyroelectric, and all pyroelectrics are also piezoelectric,
afaik.

NOPE. PIR=Passive Infra-Red.
Click to expand...
You guys really ought to give up nitpicking for Lent. They use
polyvinylidene fluoride (PVDF) pyroelectric film, which is both
piezoelectric and pyroelectric. I used to make similar things for a
living (see Footprints, http://electrooptical.net/#footprints).

Do any of you know any _active_ thermal IR detectors?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
 
David Nebenzahl wrote:
Jim Yanik wrote:

NOPE. PIR=Passive Infra-Red.

Nope.

They can be called that, but they are also called pyroelectric (look it
up if you don't believe me). And no, I don't think they have anything to
do with piezoelectricity; they are, after all, passive elements.
Click to expand...

They are 'passive', as opposed to the earlier break beam detectors
that were a two piece detector.


--
Greed is the root of all eBay.
 
Do any of you know any _active_ thermal IR detectors?
Click to expand...
I assume you mean that sarcastically. One does not detect a particular form
of radiation by _emitting_ it.
 
On 2/23/2010 6:26 PM, William Sommerwerck wrote:
Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular form
of radiation by _emitting_ it.
Click to expand...
Right. So "passive IR detector" is unnecessarily redundant. ;) But
it's the nitpicking based on little or no knowledge that I'm teasing
them about. (Of course, this being Usenet, I shouldn't be too shocked.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm1o6e$lb2$1@news.eternal-september.org:

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular
form of radiation by _emitting_ it.
Click to expand...
that's the way microwave detectors work,like the ones at your grocery store
or in burglar alarms. the klystron emits uWave radiation and then detects
the reflected energy,takes the Doppler difference as an output.
OTOH,auto radar detectors are "passive" detectors.

--
Jim Yanik
jyanik
at
localnet
dot com
 
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:4B845235.4020607@electrooptical.net:

On 2/23/2010 8:56 AM, Jim Yanik wrote:
Phil Hobbs<pcdhSpamMeSenseless@electrooptical.net> wrote in
news:4B830EC4.3030304@electrooptical.net:

On 2/21/2010 8:41 PM, David Nebenzahl wrote:
On 2/21/2010 4:12 PM David Nebenzahl spake thus:

I'd like to get responses, ideally, from folks who actually know
how these things work, and not the usual Usenet speculation.

I install a lot of motion-detector lights for clients. A lot of
these installations are problematic. I just adjusted one for the
third or fourth time because the light was staying on all the
time, even though the sensor unit (I replaced the entire unit with
a Heath-Zenity sensor recently) was working properly.

It might help for me to know how, exactly, these sensors work. By
"sensors" I mean the actual sensor, as well asw the entire unit
with the support electronics.

So I found this circuit out there in the wild:

http://www.freeinfosociety.com/electronics/schemview.php?id=2074

It uses something called a PIR. Does that stand for piezoelectric
infrared? I've seen other references to piezo sensors: how do those
work? Do they both send and receive a signal? (The device shown
here is a 3-terminal thingie.)


Close--pyroelectric, and all pyroelectrics are also piezoelectric,
afaik.

NOPE. PIR=Passive Infra-Red.


You guys really ought to give up nitpicking for Lent. They use
polyvinylidene fluoride (PVDF) pyroelectric film, which is both
piezoelectric and pyroelectric. I used to make similar things for a
living (see Footprints, http://electrooptical.net/#footprints).
Click to expand...
Doesn't matter;the sensors are -still- "passive" detectors.
Do any of you know any _active_ thermal IR detectors?

Cheers

Phil Hobbs
Click to expand...
Not "thermal" IR.

But the technique IS used in other IR wavelengths.

--
Jim Yanik
jyanik
at
localnet
dot com
 
"Jim Yanik" <jyanik@abuse.gov> wrote in message
news:Xns9D28CA8866CF0jyaniklocalnetcom@216.168.3.44...
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm1o6e$lb2$1@news.eternal-september.org:

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular
form of radiation by _emitting_ it.

that's the way microwave detectors work,like the ones at your grocery
store
or in burglar alarms. the klystron emits uWave radiation and then detects
the reflected energy,takes the Doppler difference as an output.
OTOH,auto radar detectors are "passive" detectors.
Click to expand...
These are not microwave detectors, but /motion/ detectors using microwaves.

Please think about it.
 
"Jim Yanik"


that's the way microwave detectors work,like the ones at your grocery
store
or in burglar alarms. the klystron emits uWave radiation
Click to expand...

** Errr - it might be a Gunn diode....



... Phil
 
On Tue, 23 Feb 2010 15:26:02 -0800, "William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular form
of radiation by _emitting_ it.
Click to expand...
No? What about reflective detection? For example illuminating night scene
with IR LEDs and using IR camera and motion detect in software? Not quite
the focus on cheap PIRs, but more secure uses are more likely to avoid PIRs'
false alarms.

Grant.
--
http://bugs.id.au/
 
"Grant" <g_r_a_n_t_@bugs.id.au> wrote in message
news:a6v8o5ttgltul9cih398u7hi93n8j54fvk@4ax.com...
On Tue, 23 Feb 2010 15:26:02 -0800, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:
Click to expand...

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular
form
of radiation by _emitting_ it.

No? What about reflective detection? For example illuminating night scene
with IR LEDs and using IR camera and motion detect in software? Not quite
the focus on cheap PIRs, but more secure uses are more likely to avoid
PIRs'
false alarms.
Click to expand...
Let me put this a different way... If you're trying to receive an FM radio
station, you do not emit a VHF signal to do so.

The person who posted this comment (see above) agreed with me. There is no
such thing as an _active_ thermal IR detector.
 
Jim Yanik wrote:
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm1o6e$lb2$1@news.eternal-september.org:

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a particular
form of radiation by _emitting_ it.




that's the way microwave detectors work,like the ones at your grocery store
or in burglar alarms. the klystron emits uWave radiation and then detects
the reflected energy,takes the Doppler difference as an output.
OTOH,auto radar detectors are "passive" detectors.
Click to expand...

They use Gunn diodes, not Klystrons.


--
Greed is the root of all eBay.
 
On 2/23/2010 6:34 PM William Sommerwerck spake thus:

Let me put this a different way... If you're trying to receive an FM radio
station, you do not emit a VHF signal to do so.
Click to expand...
Nor any other kind of signal.

The person who posted this comment (see above) agreed with me. There is no
such thing as an _active_ thermal IR detector.
Click to expand...
Therefore all IR detectors are passive. Therefore "passive IR detector"
is as redundant as "ATM machine", "PIN number", etc.

Therefore the correct term is *probably* pyroelectric IR detector, just
as I said somewhere up there in the receding fogs of this thread ...


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"
 
On Feb 23, 2:27 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
David Nebenzahl wrote:

Jim Yanik wrote:

NOPE. PIR=Passive Infra-Red.

Nope.

They can be called that, but they are also called pyroelectric (look it
up if you don't believe me). And no, I don't think they have anything to
do with piezoelectricity; they are, after all, passive elements.

   They are 'passive', as opposed to the earlier break beam detectors
that were a two piece detector.

--
Greed is the root of all eBay.
Click to expand...
A great technology.... Too bad most of the light fixtures you buy now
days are garbage. I've got ones that I've put in for clients that
have worked for 15 years, and many installed within the last 5 years
that have just fallen apart and/or burnt up internally.

Thanks for giving me something to read about tonight...
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm1the$7er$1@news.eternal-september.org:

"Jim Yanik" <jyanik@abuse.gov> wrote in message
news:Xns9D28CA8866CF0jyaniklocalnetcom@216.168.3.44...
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm1o6e$lb2$1@news.eternal-september.org:

Do any of you know any _active_ thermal IR detectors?

I assume you mean that sarcastically. One does not detect a
particular form of radiation by _emitting_ it.

that's the way microwave detectors work,like the ones at your grocery
store
or in burglar alarms. the klystron emits uWave radiation and then
detects the reflected energy,takes the Doppler difference as an
output. OTOH,auto radar detectors are "passive" detectors.

These are not microwave detectors, but /motion/ detectors using
microwaves.

Please think about it.
Click to expand...
Just as the IR sensors are MOTION sensors. Think about it.

--
Jim Yanik
jyanik
at
localnet
dot com
 
These are not microwave detectors, but /motion/ detectors
using microwaves.

Please think about it.

Just as the IR sensors are MOTION sensors. Think about it.
Click to expand...
You're confusing what the device does with how the sensor works.
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:hm3ajq$ogd$1@news.eternal-september.org:

These are not microwave detectors, but /motion/ detectors
using microwaves.

Please think about it.

Just as the IR sensors are MOTION sensors. Think about it.

You're confusing what the device does with how the sensor works.
Click to expand...
check the topic again.

--
Jim Yanik
jyanik
at
localnet
dot com
 
These are not microwave detectors, but /motion/ detectors
using microwaves.

Please think about it.

Just as the IR sensors are MOTION sensors. Think about it.

You're confusing what the device does with how the sensor works.

check the topic again.
Click to expand...
The infrared sensor in a motion sensor is not the motion sensor itself.
 
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