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PICList Thread
'[OT] IR Motion Sensors'
1999\03\15@112509 by Howard McGinnis

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An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)
with an goal of seeing if I could interface the sensor to a PICS.  The IR
sensor appears to be a three leaded device in a can with a window. I can't
see any numbers on the device.

Any ideas on what or how the part functions?

Howard
Howard McGinnis
spam_OUThmcginniTakeThisOuTspamdigital.net
Electronic Visions, Inc.
1650 Barrett Drive
Rockledge FL 32955
(407) 632-7530
http://ddi.digital.net/~hmcginni
.....mcginnisKILLspamspam@spam@e-visions.com

1999\03\15@122249 by mlsirton

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Hi,

On 15 Mar 99 at 11:28, Howard McGinnis wrote:
> An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)
> with an goal of seeing if I could interface the sensor to a PICS.  The IR
> sensor appears to be a three leaded device in a can with a window. I can't
> see any numbers on the device.
>
> Any ideas on what or how the part functions?

I am not 100% percent sure but this device could be something like a
phototransistor sensitive to low IR?  To interface to the PIC you
would need to amplify the signal, band-pass filter (to reject DC
and certain HF noise) it and test it with a comparator.  Another
thing is that without the cheapo plastic lens it's useless as a
motion detector.  The lens is designed to give big variations as a
warm body moves through the dectection area.

If your intention is to detect motion you're probably best using the
whole packaged sensor - it basically just has an on/off output and
12V input.

Hope this helps,
Guy - mlsirtonspamKILLspaminter.net.il

1999\03\15@122834 by Byron A Jeff

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>
> An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)
> with an goal of seeing if I could interface the sensor to a PICS.  The IR
> sensor appears to be a three leaded device in a can with a window. I can't
> see any numbers on the device.
>
> Any ideas on what or how the part functions?

I took a crack at this a while ago. Perhaps to diassembled too much.

Here's my take on it. The PIR turns on the lights when activated, so use
the light as the interface. Yes it involves 120V AC but it can be safely and
easily interfaced at the PIC.

Here's what I did. I disassembled the light fixtures. Each light had a two
wire 120VAC interface that became active when the sensor went off. I ran
the wires through a 10K 2W resistor (limiting current to 12ma) and an
optocoupler LED with a reversed biased LED. The net output was a isolated
12V signal that I ran back to the PIC and isolated again using another
optocoupler. I know I could have run the 12V signal directly into the PIC
but I was just being paranoid.

Whenever the PIR went off, the PIC received a nice stable 60 Hz signal. With
the reversed biased LED on the PIC, I even got a nice light that went off
when the PIR was activated.

BTW Home Depot here in Atlanta regularly has these PIR lights on sale for
$9.

Finishing up my security system is yet another thing on my massive list of
things to do...

Hope this helps,

BAJ

1999\03\15@124737 by mlsirton

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Hi again,

On 15 Mar 99 at 11:28, Howard McGinnis wrote:
> An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)

Previous I was talking generally about IR motion sensors.  Those
that are sold as one unit with the spot lights usually have a relay
in them (do you hear a click as the light turns on?), you could
connect to this relay.  As for the operating voltage of the sensor
itself it's very likely to be 12V DC but to be sure you would need to
measure it with a volt-meter when live (take care not to touch
anything "hot", temperature or voltage).

Guy

1999\03\15@125731 by John Mitchell

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On Mon, 15 Mar 1999, Guy Sirton wrote:

> Hi again,
>
> On 15 Mar 99 at 11:28, Howard McGinnis wrote:
> > An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)
>
> Previous I was talking generally about IR motion sensors. [...]
>
> Guy


Check this out: "Hacking a Cheap PIR Motion Sensor" by Pete McCollum
       http://www.seattlerobotics.org/encoder/nov98/pirhack.html


- j

1999\03\15@141101 by Nick Taylor

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Howard - -
Check this link and see if it matches your IR detector.
www.sharpmeg.com/products/opto/pdf/gp1u58y.pdf
On *most* can type detectors the pin nearest the side is
pin-3 (gnd), the middle pin is pin-2 (Vcc  +5V), and the
remaining pin is pin-1 (~Vout ).  The output line may
require a pullup resistor (10k should be ok).
Enjoy,
- - - Nick - - -

Howard McGinnis wrote:
<snip>
> An off topic, maybe - I disassembled a cheap IR motion sensor light ($13)
> with an goal of seeing if I could interface the sensor to a PICS.  The IR
> sensor appears to be a three leaded device in a can with a window. I can't
> see any numbers on the device.
> Any ideas on what or how the part functions?

1999\03\15@142323 by Wagner Lipnharski

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IR Motion Sensors operates by changes in the IR energy
level received during a short period of time.
At power on, it takes few seconds to develop the average
IR received and store that level in a capacitor with a
long RC constant (seconds).  The incomming IR energy
level is compared to the capacitor average, and if the
differencial is bigger than some defined trigger point
the "alarm" goes off  (isn't strange to say "alarm goes
off"? looks like the alarm went disabled).  If the IR
incomming change is very slow, it will be integrated at
the "average" capacitor, and it will not trigger the
alarm.  This is why you can just move very slowly in
front of a IR detector without trigger it.
This shows you that is possible to build a IR motion
detector using a simple pulsing IR LED (transmitter)
and a highly amplified IR receiver, based on changes
in the incomming signal.

Some car alarms use that principle, they just measure
the battery voltage and integrate it to an internal
capacitor, then keep comparing battery voltage x
capacitor voltage.  When a car door is open, the courtesy
door lamp will drop the battery voltage a few millivolts,
enough to trigger the alarm.  This kind of alarm requires
only two wires, one to ground, another to the battery
positive connection.
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\15@173843 by steve

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> IR Motion Sensors operates by changes in the IR energy
> level received during a short period of time.
> At power on, it takes few seconds to develop the average
> IR received and store that level in a capacitor with a
> long RC constant (seconds).

The nett effect is the same, but this isn't what happens in the
sensor.

The sensing element is a semiconducting crystal (Lithium tantalate
from memory) which develops a voltage depending on its absolute
temperature. It absorbs IR radiation which causes it to heat up. It
also quite "leaky" and the charge across the crystal equalises fairly
quickly so it performs its own averaging. Motion sensors come with an
inbuilt JFET to amplify the minute signals and there is only an
output if the rate of change in IR is faster than the decay rate of
the crystal. Obviously it is sensitive to thermal noise so a bit of
signal conditioning is required before triggering.
The multi-faceted lens (which is a different thing to a Fresnel lens)
ensures that a slow moving object causes relatively rapid transitions
to the IR sensor by moving in and out of the sensors field of view.

If you take the same sensor and put a mechanical chopper in front of
it you can make your own non-contact thermometer (although that
isn't what the commercial ones do). Get lots and make a thermal
imaging camera. :-)

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: .....stevebKILLspamspam.....tla.co.nz      fax +64 9 820-1929
======================================================

1999\03\16@095126 by : Cassie Carstens

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Nick
I think Howard is refering to a  PASSIVE IR sensor, not the rome control
tipe.........
Cassie
> Howard - -
> Check this link and see if it matches your IR detector.
> www.sharpmeg.com/products/opto/pdf/gp1u58y.pdf
> On *most* can type detectors the pin nearest the side is
> pin-3 (gnd), the middle pin is pin-2 (Vcc  +5V), and the
> remaining pin is pin-1 (~Vout ).  The output line may
> require a pullup resistor (10k should be ok).
> Enjoy,
>  - - - Nick - - -

1999\03\16@103248 by : Cassie Carstens

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Wagner wrote.....
> IR Motion Sensors operates by changes in the IR energy
> level received during a short period of time.

This with ref to the security device iitself. However the sensor
itself has two power supply pins and an output. The output changes in
relation to the heat source activated in front of it. But the sensor
get 'saturated' if the source stays in front and the voltage swings
back to zero. Removing the heat source once again swings the voltage.
You will have to put a shutter in front of the sensor to check the
intensity of the source. Eg. cut off the passage to the passive ir sensor
and then open it. Difficult to get a meaningfull signal.
Hope this helps. I was hoping to 'scan' an area, say from left to
right to find the hottest spot and the scan vertical for the same and
at the crossing aim a shotgun........
BTW. who gets jailed if this thing hurts someone. One certainly does
not if your dog, that was trained to kill, does that.....
Regards
Cassie

1999\03\16@114056 by Wagner Lipnharski

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: Cassie Carstens wrote:
I was hoping to 'scan' an area, say from left to
> right to find the hottest spot and the scan vertical for the same and
> at the crossing aim a shotgun........

Cheap b/w video pin cameras can do this job easily.
It doesn't need high resolution, since looks like there is not such
thing of good resolution in actual infra-red technology, except the
expensive ones.

Ironically, those cheap b/w video cameras, can receive a wide
spectrum of light, including infra-red "with great sensitivity".

For tests, I bought one of those "toy" cameras, b/w, works with
4 x AA cells and a cable to connect at the VCR, cost was $35.00.
Disassembling it, the complete video circuit is a small board
less than a square inch. The only connections are;  +Vcc, Ground,
Video Output. It is a composed video signal, with syncs.
Comes with an attached lens over the sensor chip.

At the dark, using a ordinary IR remote control as iluminator,
this camera shows at the TV a person's face at one meter away.

I wonder if somebody already did a software to analyze video
signals with a PIC unit, even that not reading all the bandwidth
existent in a video signal, but something, like 64 dots per
horizontal line is only 33k6Bits per frame, 672kBits/second.

One can say that it is not totally necessary to read all the
525 lines of signal, so reading one each eight, will give a
dot matrix image of 64 x 64, so 4096 bits to analyze, but the
reading bandwidth at that one line readed still 672kHz/second,
if reading 64 dots per line.

Using a cheap 8 bits ADC, it would be easy to locate the
high concentration of IR in the image, as the X-Y coordinates
you said above, as the "+" cross-hair target.

The V and H syncs, that need to be decoded, could trigger
interrupts to the PIC, so the data analyzes routines would
know what is going on.

To scan all the image, single delays and counters could be
produced, so the second reading could get the line #2 of each
horizontal 8 lines, the third reading gets the #3, and so on,
until after 8 readings, all the 525 lines were readed, 65
at a time.
A horizontal line has 63.5 us of time, so the 64 readings
need to happens inside that time window.  It means one reading
each microsecond aprox.  If at the second reading of the same
line, the circuit waits half microsecond (500ns) before starts
to read one bit each microsecond, it will get the intermediate
IR level between two dots readed at the first scan. If instead
to wait 500ns, it waits steps of 100ns, in 10 scans of the
same line it can scan 640 dots per horizontal line.
This is a way to scan a high speed signal with a low speed
processor.

Any idea or volunteer?

Wagner

1999\03\16@120609 by John Mitchell

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On Tue, 16 Mar 1999, Wagner Lipnharski wrote:

> : Cassie Carstens wrote:
>  I was hoping to 'scan' an area, say from left to
> > right to find the hottest spot and the scan vertical for the same and
> > at the crossing aim a shotgun........
>
> Cheap b/w video pin cameras can do this job easily.
[...]
> I wonder if somebody already did a software to analyze video
> signals with a PIC unit, even that not reading all the bandwidth
> existent in a video signal, but something, like 64 dots per
> horizontal line is only 33k6Bits per frame, 672kBits/second.

You're better off paying the extra 10-20 bucks and getting a all-digical
camera, like the QuickCam or EggCam.  QuickCam is very widespread, but has
poor 3rd-party support.  EggCam I saw referenced on the "QuickCam support
sucks" page, but dont know anything about it.



- j

1999\03\16@123727 by Wagner Lipnharski

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John Mitchell wrote:
> > I wonder if somebody already did a software to analyze video
> > signals with a PIC unit, even that not reading all the bandwidth
> > existent in a video signal, but something, like 64 dots per
> > horizontal line is only 33k6Bits per frame, 672kBits/second.
>
> You're better off paying the extra 10-20 bucks and getting a all-digical
> camera, like the QuickCam or EggCam.  QuickCam is very widespread, but has
> poor 3rd-party support.  EggCam I saw referenced on the "QuickCam support
> sucks" page, but dont know anything about it.

I imagine that inside that little video camera board, the receiver
image chip is all digital, except for the output video signal that
must be analog in some way.  All the syncs and other pulses must
be digital, so a nice "surgery-not-shaking-hands" could save few
$, but yes, a digital camera would be easier, if not color camera,
since looks like color cameras loose hat infra-red sensitivity.
Wagner

1999\03\16@232726 by Mark Willis

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: Cassie Carstens wrote:
> <snipped>
> Hope this helps. I was hoping to 'scan' an area, say from left to
> right to find the hottest spot and the scan vertical for the same and
> at the crossing aim a shotgun........
> BTW. who gets jailed if this thing hurts someone. One certainly does
> not if your dog, that was trained to kill, does that.....
> Regards
> Cassie

 AHEM.

 I'm not a lawyer etc. etc. <#include std.disclaimer.h>

 Things may be different where you live, but...

 Here in WA state, you are civilly liable if your dog bites someone,
and your dog can be killed.  Unless it's a police dog or maybe a
security dog, and you have a DARN good reason to be training it to
"kill", you'd get in trouble.

 Your right to any kind of self-defense (in WA state anyways) ends when
you've STOPPED an attacker;  They have to be a viable threat, you have
to feel seriously threatened, and you have to do nothing to escalate the
situation.

 Let's say you make a mechanism to shoots someone, what if it's the
neighbor's toddler who wandered around late one night, curious about the
stars and wanting to walk in your yard?  Want that on your conscience?
You'd end up sued into bankruptcy in WA state, I'm pretty certain.  And
I doubt that your financial situation would be tops on your mind...

 Like any other tool, a firearm needs conscious control, IMHO.  I could
see turning your lawn sprinklers on, definitely, THAT should be a nice
"disincentive" for a toddler or burglar - Track them with a spotlight,
add the sprinkler if the system figures out it's not you returning
home...  Don't add the CS gas until they get to 10 feet from your door,
then fire up the electric shock wiring, they're nicely pre-wetted <G>
THAT you can probably get away with, so long as it's really hard to show
you only intended to stop someone...

 Again, IANAL, etc. etc.

 Mark

1999\03\24@165434 by paulb

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Last word on the actual sensor chips, irrespective of dogs, electric
fences etc.

 Unless the quest for cheapness at all costs has recently overridden
commonsense, these chips are *differential* sensors.  If you look at it
to confirm, you will discern left- and right-hand sensing areas.  Used
with the segmented Fresnel lens, this makes the unit very sensitive to
movement across the field of view, very insensitive to variations in
general intensity.

 Exactly as you would wish for the intended purpose, but very difficult
to use with a chopper for absolute measurements.
--
 Cheers,
       Paul B.

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