Subject:
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Re: Light sensor values
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 17 Sep 1999 23:17:54 GMT
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Viewed:
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544 times
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In lugnet.robotics, Jeffrey Hazen writes:
> One the raw note, my CdS cell (which measures about 20K ohms in the near • dark, and about 500 ohms
> pointed at the florescent light) returns raw values between 1000 (pointed • into a dark blue coffee cup) to
> 48 (pointed directly at the light with a focusing mirror). I hope to use • this large dynamic range to
> differentiate between different objects in the room....
I have a CdS based light sensor but do not use it often because of the slow
response to changing light conditions. I know CdS cells can vary widely and I
would like to know if anyone has found a good brand that responds quickly to
changes in light levels.
The light sensor I built takes over 5 seconds to change values completely when
going from a bright room to darkness, or vice versa. My infrared detector
(which is based on a phototransistor) has no noticable response time (much
like the official Lego sensor). Has anyone done better with various CdS cells?
On a (somewhat) related note: How would it be possible to use three light
sensor, with some sort of colored filter setup to differentiate color? Most
importantly is there any way to combine thier input into one sensor port? I
can image some ways using two ports, but if there was some way to use the raw
value to tell predominant color (say 0 - 300 for red, 400-700 for blue, etc..)
from one port, that would be interesting.
Richard
richard at mailstart dot com
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Message has 1 Reply:
 | | Re: Light sensor values
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| Richard <richard@mailstart.com> wrote in message news:FI88pu.4Js@lugnet.com... (...) when (...) cells? CdS sensors are pretty slow, but I don't think the ones I'm using take 5 seconds. I have used the Radio Shack 276-1657 and the Mouser 338-54C348 (...) (25 years ago, 18-Sep-99, to lugnet.robotics)
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Message is in Reply To:
| | RE: Light sensor values
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| One the raw note, my CdS cell (which measures about 20K ohms in the near dark, and about 500 ohms pointed at the florescent light) returns raw values between 1000 (pointed into a dark blue coffee cup) to 48 (pointed directly at the light with a (...) (25 years ago, 17-Sep-99, to lugnet.robotics)
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