Subject:
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Re: COLOR light sensor
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Thu, 29 Nov 2001 00:07:08 GMT
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Viewed:
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1741 times
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David Schilling wrote:
>
> In lugnet.robotics.rcx, John Barnes writes:
> > The device works as follows;
> >
> > The heart of the thing is a small PIC microcontroller which drives four
> > different coloured LEDs in sequence and reads the returned energy from the
> > object in front of the device of unknown colour. It also samples the level
> > when no LEDs are on so it can back off the ambient light level. One LED is
> > IR. It is used to detect the presence of an object. The other LEDs are blue,
> > red and green. The microcontroller takes the values from the three colours
> > and normalizes them to allow for different overall diffuse reflection
> > efficiency. Then it uses a rather arbitrary process to decided based on the
> > relative magnitudes of the three colours where abouts on the spectrum, the
> > colour is most likely to lie. It then outputs this to a DAC which drives the
> > constant current transistor to feed the response back to the RCX. When no
> > object is present, the response is forced to 0. When an object is present,
> > the response is either in the range 10 - 90 if a colour is deemed to be
> > present, or jammed to 100 if the RGB components are equal enough to signify
> > white.
>
> VERY interesting! I was just talking with someone at the last SMART meeting
> how cool it would be if there was a colour light sensor. I can't wait to
> read more about it! Keep us informed how you do with it.
>
> I'm not exactly sure what a reading between 10-90 would represent. A guess
> is 10=red, 90=violet. Is that what you had in mind? I don't like the
> forcing to 100 for white, because that doesn't let you 'see' the spectrum of
> greys!
>
> Personally I would prefer being able to read the four values independantly,
> and let the software determine what they mean. The sensor would return them
> in sequence, starting with the IR, which would have 512 added to it's value,
> and the other three values would be guaranteed to be under 512, and would be
> returned in the order Red, Green, and Blue.
Would it not be better to have 3 'eyes' each with a different filter.
Red, Blue and green coloured filters. We used to do this for digitizing.
Doesn't this application following the same rules? Since each 'eye'
would have a different reading you could do something to make it mean
sense to the RCX.
Just my thoughts...
Dean
--
Dean Husby
LUGNET Member #320
TFM's LEGO Workshop - http://www.akasa.bc.ca/tfm
The Vancouver LEGO Club - http://www.akasa.bc.ca/vlc/
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Message is in Reply To:
 | | Re: COLOR light sensor
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| (...) VERY interesting! I was just talking with someone at the last SMART meeting how cool it would be if there was a colour light sensor. I can't wait to read more about it! Keep us informed how you do with it. I'm not exactly sure what a reading (...) (23 years ago, 28-Nov-01, to lugnet.robotics.rcx)
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