How motion sensors work

[David Nebenzahl]

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.

I know *generally* how these work: so far as I know, the sensor detects
heat, so I'm guessing it's an infrared receptor of some sort.

What would help are knowing such things as what the actual "angle of
view" of these sensors are (I know this is usually given on the box, but
I wonder how accurate those figures are and how much is hype when they
say the sensor has a 270° range), what their effective distance range
is, what kind of response curve (distance/temperature of radiating
body/response) they have, and what kinds of effects due to reflection
one needs to be aware of.

Of course, it's possible there's already a document out there somewhere
in Internet-land that explains all this; if there is, and if you know
about it, I'd appreciate a link.

It might even be fun to get one of the "raw" sensors and play around
with it on a test bench, maybe try to characterize it myself. Remember,
my goal here is to be able to install these things (motion-activated
lights) so that they actually work correctly. As things stand now, it's
often a crap shoot. And yes, there are often defective components. This
last installation was typical, where the sensor unit had simply failed
and needed to be replaced. (And if anyone knows which units are better
than which others, that too would be valuable information.)

Thanks in advance.


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

- a Usenet "apology"

 

On Sun, 21 Feb 2010 16:12:04 -0800, David Nebenzahl
<nobody@but.us.chickens> wrote:

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.

I know *generally* how these work: so far as I know, the sensor detects
heat, so I'm guessing it's an infrared receptor of some sort.

What would help are knowing such things as what the actual "angle of
view" of these sensors are (I know this is usually given on the box, but
I wonder how accurate those figures are and how much is hype when they
say the sensor has a 270° range), what their effective distance range
is, what kind of response curve (distance/temperature of radiating
body/response) they have, and what kinds of effects due to reflection
one needs to be aware of.

Of course, it's possible there's already a document out there somewhere
in Internet-land that explains all this; if there is, and if you know
about it, I'd appreciate a link.

It might even be fun to get one of the "raw" sensors and play around
with it on a test bench, maybe try to characterize it myself. Remember,
my goal here is to be able to install these things (motion-activated
lights) so that they actually work correctly. As things stand now, it's
often a crap shoot. And yes, there are often defective components. This
last installation was typical, where the sensor unit had simply failed
and needed to be replaced. (And if anyone knows which units are better
than which others, that too would be valuable information.)

Thanks in advance.

If you really want a detailed explanation, you can find several online
- there are different detection technologies and there are dfferent
types of lenses, which affect the field of view.

My experience is that aim is the key to reliable operation, regardless
of the motion sensor brand. Unless you are very fimiliar with a
specific unit under different conditions, it's unlikely that you will
get the aim correct the first (second/third) time.

Example:
There is a Zenih motion sensor light on the corner of the house. It
faces a side street which is about 5 feet lower than the ground at the
side of the house. If the motion sensor is aimed for people
detection at 10-15 feet, a vehicle turning into the side street
can trip it. If the motion sensor is aimed down enough to avoid
vehicle trips, it doesn't see people until they are within about 5
feet of the sensor, which is about 10 feet off the ground.

I've used a similar motion sensor light on level or up-sloping ground
and had much more reliable operation (longer range sensing, fewer
false detections).

John

 

[David Nebenzahl]

On 2/21/2010 5:12 PM news@jecarter.us spake thus:

My experience is that aim is the key to reliable operation, regardless
of the motion sensor brand. Unless you are very fimiliar with a
specific unit under different conditions, it's unlikely that you will
get the aim correct the first (second/third) time.

Example:
There is a Zenih motion sensor light on the corner of the house. It
faces a side street which is about 5 feet lower than the ground at the
side of the house. If the motion sensor is aimed for people
detection at 10-15 feet, a vehicle turning into the side street
can trip it. If the motion sensor is aimed down enough to avoid
vehicle trips, it doesn't see people until they are within about 5
feet of the sensor, which is about 10 feet off the ground.

I've used a similar motion sensor light on level or up-sloping ground
and had much more reliable operation (longer range sensing, fewer
false detections).

Well, sure, aim seems to be about 85% of the trick here. And certainly
having a sensor looking out on level or upsloping ground is ideal. The
problem with my last installation was that the light with attached
sensor was under the eave of the house looking straight down on a
driveway below. Apparently the main problem was that the heat from the
lights was keeping the sensor on; turning the lights away from the
sensor seems to have fixed it. (Makes a good case for using CFLs, except
that they're bad on two counts: take too long to come up to full
brightness, and aren't supposed to work correctly with most sensors,
being a non-resistive load.)


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

- a Usenet "apology"

 

[David Nebenzahl]

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.)


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

- a Usenet "apology"

 

[David Nebenzahl]

On 2/21/2010 5:41 PM David Nebenzahl spake thus:

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.)

My guess was wrong; it's "pyroelectric", not piezo.

Hey, whaddya know; actually found useful stuff Googling, like this page
that has a pretty good explanation plus a schematic:

http://www.glolab.com/pirparts/infrared.html


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

- a Usenet "apology"

 

[Phil Allison]

"David Nebenzahl"

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.

See:

http://en.wikipedia.org/wiki/Passive_infrared_sensor




..... Phil

 

[William Sommerwerck]

Motion sensors are weird. The sensor itself is a piece of piezoelectric
plastic that has been used to make tweeters (most notably by Pioneer).

Oddly, these sensors generate a voltage when exposed to infrared. The
fluctuations in this voltage (as a warm body moves in front of the sensor)
can be capacitor-coupled to a FET for amplification.

 

[David Nebenzahl]

On 2/21/2010 5:47 PM Phil Allison spake thus:

"David Nebenzahl"

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.

See:

http://en.wikipedia.org/wiki/Passive_infrared_sensor

Sorry, I don't rely on Wikipedia, "the 'encyclopedia' that any
pimple-faced 7th grader can edit", for any credible information.


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

- a Usenet "apology"

 

[Michael A. Terrell]

David Nebenzahl wrote:

On 2/21/2010 5:41 PM David Nebenzahl spake thus:

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.)

My guess was wrong; it's "pyroelectric", not piezo.

Hey, whaddya know; actually found useful stuff Googling, like this page
that has a pretty good explanation plus a schematic:

http://www.glolab.com/pirparts/infrared.html

Passive Infra Red, meaning that it doesn't have its own IR source.
It works from a pair of IR sensors, and looks for a difference in the IR
level on the pair. That is why it takes a few seconds to a minute for
them to settle when first powered up. Some early PIR detectors came
with several sets of lenses to adjust the beam width & height. You
looked at the manual and picked the one you needed for the desired
operation.

<http://www.google.com/search?num=100&hl=en&newwindow=1&safe=off&client=firefox-a&rls=org.mozilla:en-USfficial&ei=JeeBS-muLtPX8Aap-PGMBA&sa=X&oi=spell&resnum=0&ct=result&cd=1&ved=0CAsQBSgA&q=Passive+Infrared&spell=1>


--
Greed is the root of all eBay.

 

[Michael A. Terrell]

David Nebenzahl wrote:

On 2/21/2010 5:47 PM Phil Allison spake thus:

"David Nebenzahl"

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.

See:

http://en.wikipedia.org/wiki/Passive_infrared_sensor

Sorry, I don't rely on Wikipedia, "the 'encyclopedia' that any
pimple-faced 7th grader can edit", for any credible information.

Good for you. The first PIR for the consumer market was a motion
sensor for burglar alarms. It ran on a lithium battery, and was sold as
a "Passive Infrared Detector". I tested one from the first production
run, decades ago.


--
Greed is the root of all eBay.

 

[Phil Allison]

"David Nebenzahl"

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.

See:

http://en.wikipedia.org/wiki/Passive_infrared_sensor

Sorry, I don't rely on Wikipedia,

** No need to *rely* on wiki - but it is usually a good starting point in
a quest for the basic facts on a great many topics.

Other web sites are JUST as likely or MORE likely to contain serious
errors or give misleading information.

In any case, I never post a link unless I have read it through and reckon
the info is good.


"the 'encyclopedia' that any pimple-faced 7th grader can edit", for any
credible information.


** You are in NO position to decide what is credible and what is not.

Cos you are a trolling, brainless cretin.



...... Phil

 

[William Sommerwerck]

You are in NO position to decide what is credible and what is not.
Cos you are a trolling, brainless cretin.

And /your/ qualifications are...?

 

[Phil Allison]

"William Sommerwanker"


** FOAD you RIDICULOUS ARSEHOLE !!




..... Phil

 

[Wild_Bill]

FWIW, the detector's field/pattern can be changed with opaque material-black
tape placed on the lens (sides and/or top/bottom).

For a narrow field, applying pieces of vertically-oriented tape to the sides
of the lens area reduces the field to a more narrow pattern.

Putting the tape (or opaque paint) on the inside would look more
professional, IMO, but the tape or other material needs to be secure so it
doesn't peel away and block the sensor.
An opaque mask could probably be fabricated and glued securely to the inside
of the lens holder portion of the enclosure.

Those are some informative links you posted.

--
Cheers,
WB
..............


"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:4b81cacb$0$2400$822641b3@news.adtechcomputers.com...

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.

I know *generally* how these work: so far as I know, the sensor detects
heat, so I'm guessing it's an infrared receptor of some sort.

What would help are knowing such things as what the actual "angle of view"
of these sensors are (I know this is usually given on the box, but I
wonder how accurate those figures are and how much is hype when they say
the sensor has a 270° range), what their effective distance range is, what
kind of response curve (distance/temperature of radiating body/response)
they have, and what kinds of effects due to reflection one needs to be
aware of.

Of course, it's possible there's already a document out there somewhere in
Internet-land that explains all this; if there is, and if you know about
it, I'd appreciate a link.

It might even be fun to get one of the "raw" sensors and play around with
it on a test bench, maybe try to characterize it myself. Remember, my goal
here is to be able to install these things (motion-activated lights) so
that they actually work correctly. As things stand now, it's often a crap
shoot. And yes, there are often defective components. This last
installation was typical, where the sensor unit had simply failed and
needed to be replaced. (And if anyone knows which units are better than
which others, that too would be valuable information.)

Thanks in advance.


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

- a Usenet "apology"

 

[David Nebenzahl]

On 2/21/2010 6:17 PM William Sommerwerck spake thus:

You are in NO position to decide what is credible and what is not.
Cos you are a trolling, brainless cretin.

And /your/ qualifications are...?

Heh; I see we both got our tickets for the Phil Allison ride here. Great
fun for free; just sign up at RoomForInsults.com and experience the
adrenaline rush as the invectives start flying!


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

- a Usenet "apology"

 

[Jeff Liebermann]

On Sun, 21 Feb 2010 17:41:17 -0800, David Nebenzahl
<nobody@but.us.chickens> wrote:

It uses something called a PIR. Does that stand for piezoelectric
infrared?

PyroElectric or Passive InfraRed sensor.

<http://www.dias-infrared.de/pdf/basics_eng.pdf>
<http://www.ladyada.net/media/sensors/BISS0001.pdf>
<http://www.glolab.com/pirparts/infrared.html>
Typical sensor:
<http://www.ladyada.net/media/sensors/RE200B.pdf>
Tutorial:
<http://www.instructables.com/id/PIR-Motion-Sensor-Tutorial/>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Michael A. Terrell]

William Sommerwerck wrote:

You are in NO position to decide what is credible and what is not.
Cos you are a trolling, brainless cretin.

And /your/ qualifications are...?

He is a mentally ill Aussie who won't stay on his prescribed
medication.


--
Greed is the root of all eBay.

 

[Phil Hobbs]

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. Porch light sensors use a pyroelectric split cell, with the two
halves wired in series, and a MOSFET connected to the point in the
middle. The MOSFET usually has a 10M gate leak resistor.

The Fresnel lens in the front is made of high density polyethylene
(HDPE), which has about 40% transmittance in the 8-14 um band. It is
actually arranged as segments of several lenses (about a dozen or so),
so it casts a dozen images of everything in the field. Warm things that
move horizontally cause warm images to move across the split detector,
making an AC waveform. The FET's output is AC-coupled into another
amplifier that drives the triac.

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

 

On Mon, 22 Feb 2010 18:09:56 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

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. Porch light sensors use a pyroelectric split cell, with the two
halves wired in series, and a MOSFET connected to the point in the
middle. The MOSFET usually has a 10M gate leak resistor.

The Fresnel lens in the front is made of high density polyethylene
(HDPE), which has about 40% transmittance in the 8-14 um band. It is
actually arranged as segments of several lenses (about a dozen or so),
so it casts a dozen images of everything in the field. Warm things that
move horizontally cause warm images to move across the split detector,
making an AC waveform. The FET's output is AC-coupled into another
amplifier that drives the triac.

Cheers

Phil Hobbs

Piezo? Pyro? I don't think so.

PIR is Passive InfraRed. Ie, it detects infrared (heat) without
actively sending out any infrared illumination.

 

[Jim Yanik]

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.

--
Jim Yanik
jyanik
at
localnet
dot com

Porch light sensors use a pyroelectric split cell, with the two
halves wired in series, and a MOSFET connected to the point in the
middle. The MOSFET usually has a 10M gate leak resistor.

The Fresnel lens in the front is made of high density polyethylene
(HDPE), which has about 40% transmittance in the 8-14 um band. It is
actually arranged as segments of several lenses (about a dozen or so),
so it casts a dozen images of everything in the field. Warm things that
move horizontally cause warm images to move across the split detector,
making an AC waveform. The FET's output is AC-coupled into another
amplifier that drives the triac.

Cheers

Phil Hobbs