Subject:
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Re: Lght Sensor & Three colors?
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Wed, 7 Feb 2001 00:04:34 GMT
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Viewed:
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1488 times
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Le Mardi 06 Février 2001 21:50, vous avez ?rit :
> I'm pretty sure there were no filters involved. This was the basic robot
> arm that can be built from the 9740(?) Control Lab Starter Set for the
> Serial Interface Box. She slightly modified it so that there were multiple
> bins for all of the different colors, and not just two bins. Maybe I'm
> exaggerating a little with the 10 colors... but let's just say that there
> were a lot of colors represented: all the standard lego colors plus pink
> and purple. She wrote the code in LEGO-LOGO (the "control lab" software).
> I wish I could remember which school they were in... I know her teacher was
> a part of the Minuteman Tech program (that pays the middle school
> technology teachers in the boston suburbs that are a part of its program),
> but I can't remember his name.
>
> In lugnet.robotics.rcx, Terry King writes:
> > Ben, did this designer use any filters? Or was this
> > simply the response of the LED and detector in the
> > Light Sensor?
I think that the identification of colors can be quite accurate, assuming
that we may need spend time for retrieving several sample values from the
sensor, and doing thus a kind of average and measure correction.
No matter if it's about colors or grayscale, because it is essentially the
re-emitted light that is measured.
Personnally, I did have made some tests in order to detect 7 colors, but as
soon as your sensor is in action on your bot, the ambient light variations
may increase the rate of identification errors. What's more if the coloured
objects you want to analyse are moving quite fast, it could not be reliable
(at all).
For the command control of an inverted pendulum for example, and for the
perception of its angular position, it was not possible to use discrete
color values, because of mistakes in color detection. But rather a gray
gradient, much more reliable.
You can also use parts of the reflective layer of a CD to surely detect a
treshold with a big peak on the sensor. Typically, a value from 110 to 125
with legOS, amazing isn't it ?
Black, White, Bright, it's a good choice !
Of course, the CD's sent by AOL are the best suited to this task, leading to
extreme pleasure when running the scissors.
--
Alexandre BEC
laleks@free.fr
http://laleks.free.fr/mindstorms/
--
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Message has 1 Reply:
 | | Re: Lght Sensor & Three colors?
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| Just a thought: Couldn't one make a "rosetta stone" wheel of the various LEGO(R) colors that uses an angle sensor for indexing them and then just compare the brick being "measured" to the known bricks on the wheel ? It'd be cumbersome, but not very (...) (24 years ago, 7-Feb-01, to lugnet.robotics.rcx)
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