# Driveway Motion Sensor

P

#### Phil

Jan 1, 1970
0
Hello
I purchased a unit a short time ago that is used to detect cars coming
into my driveway , I think it works on IR motion sensing , it does let me
know if a car or person comes down my driveway , the bad part is that the
thing gives me so many false alarms , seems to be the most problem after the
sun comes out very bright , I guess my question is in two parts , I cracked
the detection unit open and found the detector , am wondering exactly how it
does it thing and could I locate it in another container that is shielded
better , also wonder if anyone has built or used one of the magnetic
detectors that appear to be based on the metal detector principal , I hate
to dig up and put a 6 ft. diameter loop in my driveway , as an old HAM
operator , I have built a lot of IC projects and at $200.00 for commercial unit , I might just try , any comments would be appreciated. Phil Lohiser W #### Wim Ton Jan 1, 1970 0 Phil said: Hello I purchased a unit a short time ago that is used to detect cars coming into my driveway , I think it works on IR motion sensing , it does let me know if a car or person comes down my driveway , the bad part is that the thing gives me so many false alarms , seems to be the most problem after the sun comes out very bright , I guess my question is in two parts , I cracked the detection unit open and found the detector , am wondering exactly how it does it thing and could I locate it in another container that is shielded better , also wonder if anyone has built or used one of the magnetic detectors that appear to be based on the metal detector principal , I hate to dig up and put a 6 ft. diameter loop in my driveway , as an old HAM operator , I have built a lot of IC projects and at$200.00 for commercial
unit , I might just try , any comments would be appreciated.
Phil Lohiser
Maybe one of these small magnetic field sensors(Philips, Honeywell). They
are sensitive enough for a compass, so they will detect 1.5 tons of steel
from a meter distance as well.

Wim

J

#### John

Jan 1, 1970
0
Phil said:
Hello
I purchased a unit a short time ago that is used to detect cars coming
into my driveway , I think it works on IR motion sensing , it does let me
know if a car or person comes down my driveway , the bad part is that the
thing gives me so many false alarms , seems to be the most problem after
the sun comes out very bright , I guess my question is in two parts , I
cracked the detection unit open and found the detector , am wondering
exactly how it does it thing and could I locate it in another container
that is shielded better , also wonder if anyone has built or used one of
the magnetic detectors that appear to be based on the metal detector
principal , I hate to dig up and put a 6 ft. diameter loop in my driveway
, as an old HAM operator , I have built a lot of IC projects and at
$200.00 for commercial unit , I might just try , any comments would be appreciated. Phil Lohiser Hi, Phil - I had one of those. They are PIR (Pyro Infra Red) sensors which are sensitive to IR emitted by warm-bodied critters. It is sensitive to the *movement* of the warm bodies. Deer, armadillos, rabbits, raccoons, dogs, cats, mice, and other creatures can set them off. Unfortunately, so will trees and their shadows when the former is swaying in the breeze. I think it is the moving contrast between heat (light) and no heat (shadow) that triggers it. Conversely, mine occasionally missed triggering on a car when the day was cold and overcast. I think it was because the skin temperature of the car was about the temperature of the surroundings. Try to aim it away from objects that move with the wind. Try to aim it higher than a critter. You may still get a trigger from a deer. Cheers, John J #### John Jan 1, 1970 0 Phil said: Hello I purchased a unit a short time ago that is used to detect cars coming into my driveway , I think it works on IR motion sensing , it does let me know if a car or person comes down my driveway , the bad part is that the thing gives me so many false alarms , seems to be the most problem after the sun comes out very bright , I guess my question is in two parts , I cracked the detection unit open and found the detector , am wondering exactly how it does it thing and could I locate it in another container that is shielded better , also wonder if anyone has built or used one of the magnetic detectors that appear to be based on the metal detector principal , I hate to dig up and put a 6 ft. diameter loop in my driveway , as an old HAM operator , I have built a lot of IC projects and at$200.00 for commercial unit , I might just try , any comments would be
appreciated.
Phil Lohiser

Hi, Phil -

I had one of those. They are PIR (Pyro Infra Red) sensors which are
sensitive to IR emitted by warm-bodied critters. It is sensitive to the
*movement* of the warm bodies. Deer, armadillos, rabbits, raccoons, dogs,
cats, mice, and other creatures can set them off. Unfortunately, so will
trees and their shadows when the former is swaying in the breeze. I think it
is the moving contrast between heat (light) and no heat (shadow) that
triggers it.

Conversely, mine occasionally missed triggering on a car when the day was
cold and overcast. I think it was because the skin temperature of the car
was about the temperature of the surroundings.

Try to aim it away from objects that move with the wind. Try to aim it
higher than a critter. You may still get a trigger from a deer.

Cheers,
John

J

#### Jim Thompson

Jan 1, 1970
0
Hi, Phil -

I had one of those. They are PIR (Pyro Infra Red) sensors which are
sensitive to IR emitted by warm-bodied critters. It is sensitive to the
*movement* of the warm bodies. Deer, armadillos, rabbits, raccoons, dogs,
cats, mice, and other creatures can set them off. Unfortunately, so will
trees and their shadows when the former is swaying in the breeze. I think it
is the moving contrast between heat (light) and no heat (shadow) that
triggers it.

Conversely, mine occasionally missed triggering on a car when the day was
cold and overcast. I think it was because the skin temperature of the car
was about the temperature of the surroundings.

Try to aim it away from objects that move with the wind. Try to aim it
higher than a critter. You may still get a trigger from a deer.

Cheers,
John

Why not get one of those X-band door opener units.

I can also imagine using some 40KHz ceramic resonators, one
transmitting, one receiving... angle shot off the windshield ??

...Jim Thompson

M

#### mpm

Jan 1, 1970
0
I had one of those. They are PIR (Pyro Infra Red) sensors which are

Actually, it stands for "Passive Infrared".
Yes, this technology is affected by direct sunlight.
Outdoor units are available with special filters and/or software to
overcome the problems associated with outdoor use. For example, the
Optex VR-402 series.

Those of us "old enough" to remember when gas stations used to pump
the gas for you:

They had a pneumatic bell setup which seemed to be low-tech, and quite
reliable.
You could emulate this with some hose stretched across the driveway.
For the sensor, (instead of a bell), you could use a World Magnetics
pressure switch (available from Digikey).

Might look ugly (though, not to me at least), and would be much less
headache than digging up the driveway.

The magnetic loop sensors by the way, are suseptible to lightning
damage if you live in such as area. Keep that in mind.

-mpm

L

#### Luhan

Jan 1, 1970
0
Hello
I purchased a unit a short time ago that is used to detect cars coming
into my driveway , I think it works on IR motion sensing , it does let me
know if a car or person comes down my driveway , the bad part is that the
thing gives me so many false alarms , seems to be the most problem after the
sun comes out very bright , I guess my question is in two parts , I cracked
the detection unit open and found the detector , am wondering exactly how it
does it thing and could I locate it in another container that is shielded
better , also wonder if anyone has built or used one of the magnetic
detectors that appear to be based on the metal detector principal , I hate
to dig up and put a 6 ft. diameter loop in my driveway , as an old HAM
operator , I have built a lot of IC projects and at \$200.00 for commercial
unit , I might just try , any comments would be appreciated.
Phil Lohiser

Hi,

You could just buy one of those self-contained IR units used in half
the small businesses in America. It runs on 110 volts and aims at a
bicycle reflector. Just put it on posts across your driveway about 4
feet off the ground.

Luhan
http://mondo-technology.com

J
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