Re: Ultrasonic Sensors

["Robert L Bass" <robertlbass@xxxxxxxxxxx>]

>> Since they will be used outdoors, what will the issues be?
>
> Constant false alarms

True.  Also, ultrasonic detectors don't have anywhere near the gentleman's
requested range.

> What you are proposing requires "dual photo-eyes".
> A type of infrared invisible beam detector. Around
> $300 for a good set, 1 set for each perimeter side...

Outdoor photobeam detectors start around $135 for a 500 foot DS model.
IntelliSense (Honeywell) makes a 250 foot, single beam, outdoor
photoelectric that retails for $122.

Although not exactly what the gentleman asked for, Optex has an interesting
photoelectric that s designed to mount on the outside wall of the home,
providing protection for a row of windows.  It retails for $125.  There are
numerous other reasonably priced options for outdoor protection.

> This is not a DIY project.

That depends on the DIYer.  Most people have no interest in installing their
own security systems so for them it's not a DIY project.  However, those
with a modicum of tool skills and a bit of patience can DIY install a
system.  It's not rocket science.  Photoelectric detectors consist of a
transmitter and a receiver.  The devices require (at a minimum) 2-conductor
wire to the transmitter and 4-conductor wire to the receiver.  Each needs to
be mounted on a sturdy post, fence or wall.  An alignment light is clipped
to the transmitter, pointing in the direction of the receiver.  The DIYer
then adjusts the lens at the other end until a spot of light coming through
the lens rests on the sensor.  The alignment light is then moved to the
receiver end and the identical procedure is followed to align the
transmitter.  This all takes a few minutes.

The hardest part of installing outdoor photoelectric motion detectors is
running the wire.  Most of the time it's run below ground.  A tool called a
"ditch witch" can cut an 18" deep by 2" wide trench for wire burial (be sure
to use cable that is rated for direct burial and check with your building
inspector for recommended depth of the trench to avoid damage due to ground
frost in winter).

Good quality photobeams properly installed will remain aligned for several
years unless they're impacted.  When they need adjustment you take out the
alignment light and repeat the procedure above.  Periodic attention to
insects and cleaning of the lenses will keep them running for many years.
Speaking of insects, I like to douse a small piece of sponge material with
Raid and leave it inside the detector, then seal all openings with caulk or
RTV.  That generally keeps even outdoor detectors bug free for years.  Any
time you service the unit squirt a little more Raid on the sponge.  Be sure
the sponge is not in direct contact with the lens or the circuit board.

I sell outdoor photobeam detectors as well as lots of other alarm, CCTV and
automation systems online so I'm a bit biased in favor of DIY -- just as
many of the posters who install this stuff for a living are biased against
DIY.  :^_

--

Regards,
Robert L Bass

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