Subject:
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Techno-stuff Proximity Detector
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 23 Dec 1999 20:41:39 GMT
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Viewed:
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810 times
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I recently ordered and received two of Pete Sevcik's Techno-stuff Proximity
Detectors and thought I'd pass along my impressions. First, I have no
financial interest in his company except for having these two sensors which
are under warranty. Second, except for this transaction, I don't even know him.
The units are superbly well made. They come with an excellent set of
instructions that have illustrations which are much, much clearer than in one
of the recent Mindstorms books. The instructions even include sample RCX code,
but didn't include NQC versions.
The 90 day warranty was attached to the instructions, so it is unlikely that
it will be lost.
The sensors come with the cable attached. The sensors resemble the LEGO light
sensor in size and cable length, but have sightly different coloring and have
a Techno-stuff label to help differentiate them.
They work as they are intended to. I found that since these devices are IR
based, that the surface which returns the IR signal affects the apparent range
at which the detection takes place. This is not surprising. Since the sensors
give a binary indication of proximity (they are either within range or not
within range - they don't report distance to the sensed object) it is easy to
use them.
They are configured as light sensors. When they don't sense a nearby object,
they report single-digit numbers, typically 1. When they are getting close and
trying to decide if they are there yet, they rapidly flick through numbers in
the range of say 50 through 70. Once they have decided, they settle on large
numbers, typically 78 or 79. So by using either low or high transition values,
one can slightly tune the detection range. Comparing their reported value to
an intermediate number might lead to unpredictable behavior if the sensor is
momentarily indecisive.
The main range adjustment is a small switch at the back of the sensors. There
are three ranges, short, medium and long. The instructions say these represent
about 4, 8 and 12 inches, but on my very reflective walls in my hallway, it
was about 50% greater. By comparison, a sheer drapery was almost invisible to
these sensors.
These sensors have substantial field of view, around 50 degrees, so
positioning them is important.
In general I am extremely pleased with them. They are vastly easier to use
than touch-sensor bumpers.
My only regret is that I only ordered two of them. I wish I'd ordered a third!
See www.flash.net/~sevcik/ for more information.
Regards, to all, Dave Paule
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