Subject:
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Re: light sensor question
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Thu, 24 Jul 2003 07:37:13 GMT
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Viewed:
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3128 times
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On Wed, 23 Jul 2003 18:17:03 GMT
"Katie Panciera" <katie_panciera@berea.edu> wrote:
> In lugnet.robotics.rcx, Aaron Goodman wrote:
> > In lugnet.robotics.rcx, Katie Panciera wrote:
> > > I am writing a research paper about work I have done with Mindstorms this
> > > summer. One thing that I used a lot was the light sensor, but I am having a hard
> > > time finding what exactly the sensor measures. I was wondering if anyone could
> > > give me any direction as to the units of the light sensor.
> > > Thanks,
> > > Katie
> >
> > Is this what your looking for?
> > http://www.plazaearth.com/usr/gasperi/light.htm
> >
> > in terms of what units it mesures it in I don't think it really has any. it is
> > just a relative reading from 0-100.
>
> What I'm looking for is really the latter of the topics. It seems to me that it
> must have some sort of units, because I've never seen it hit zero even with
> alterations (as Ralph Hempel has described on his site). It seems like it should
> be measuring some aspect of the light. I thought that I'd read somewhere that
> the light sensor with the original firmware (I'm using brickOS) uses a scale
> from 0-1000 but rounds that off and gives you 0-100. Any other thoughts out
> there?
> K
The Analog to Digital converter of the h8/300 (the brains of the lego mindstorms) is 10 bits, so it has a range of 0-1023. I'm not sure how it converts that to the 0-100, it may do it by just dividing by 10 and rounding.
If you want to see the raw values you can use nqc to do it. As for the aspect of light it seems like it would be mesuring the intensity (how many electrons are given off when the photons hit the silicon junction).
-Aaron
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Message has 2 Replies:
 | | Re: light sensor question
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| (...) According to Kekoa Proudfoot's RCX Internals webpage ((URL) if (raw < 187) // bug? this allows percent=101, should be raw < 189 sensor->value = 64 else sensor->value = (3ff - raw) * 19 / 9c Numbers are in hexadecimal (base 16). Jürgen (21 years ago, 24-Jul-03, to lugnet.robotics.rcx)
| | | Re: light sensor question
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| (...) Here is another question...does incandescent light differ from the light given off by LEDs in terms of how the light sensor sees it? I am experimenting with some LEDs trying to get the light sensor to react and it seems to only see the light (...) (21 years ago, 26-Jul-03, to lugnet.robotics.rcx)
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Message is in Reply To:
| | Re: light sensor question
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| (...) What I'm looking for is really the latter of the topics. It seems to me that it must have some sort of units, because I've never seen it hit zero even with alterations (as Ralph Hempel has described on his site). It seems like it should be (...) (21 years ago, 23-Jul-03, to lugnet.robotics.rcx)
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