Subject:
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Re: Black
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Fri, 28 Jan 2000 18:43:22 GMT
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Viewed:
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5641 times
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I attempted to do the "black vinyl between LED and sensor" modification that
Ralph
Hempel documents on his site, but I was unable to get the vinyl to slide
between the
LED and the sensor (too tight a fit). So I used a small wire (toothpick
would do as
well) to apply a SMALL amount of testor's flat-black model paint on the side
of the LED facing the sensor. The difference between black+white on the
test pad,
with 4 frosted 60W halogen bulbs on in the ceiling fan above and the sensor
positioned
about 1cm above the pad, is now white=45, black=12. A completely dark room
(except
the pen light to read the LCD on the RCX reads as under 10, the sensor
directed at the
aforementioned ceiling fan light reads 90+ from 1 foot away.
-Peter
"Mike W. Burger" <mike@hawaii.edu> wrote in message
news:Fp0ys8.CB0@lugnet.com...
> Since I am currently working on line following, I did some tests
> with the Lego active light sensor. I mounted one on a small
> test cart pointing down a bit more than 1/8 inch above the
> "ground".
>
> The 1.5 test pad reads
>
> white 57
> black 38
> green 46
>
> I went through a book of construction paper. The results were
> surprising. This sensor sees a lot of things as white; reds,
> yellows, oranges, greys, lavenders, browns all reading 55-56,
> even 57. The construction paper black was a disapointing 47.
>
> The cheap newsprint pads from art stores were a nice surprise
> at 56 so I tried various marks on those. Magic marker nice
> and heavily done goes down to 37 (black marker). The black
> crepe photo masking tape I had high hopes for came out at
> 38-39. Black plastic tape was somewhat worse at 39-40. Red
> electrical tape was 56. This was all done with somewhat moderate
> indoor light with the test sheet flat. In high light the
> glossy finish of things like the black plastic tape will catch
> glare that might be a problem. Even the black crepe tape is
> disappointingly glossy.
>
> The best was india ink stroked on with one of the Speedball
> steel brushes. If gone over several times, or stroked on the
> back of the sheet as well, so the ink soaks through the paper
> (I use a backing sheet as blotter), it can get down to 31-32
> and very non-glossy.
>
> That is a change from 56 as a rather steady white reading when
> over the newsprint to a drop to 31-32 when over the black line
> of india ink. A range of 24 and the best I have been able to do
> so far, and quick and easy to impliment. The big pad of 50 sheets
> of newsprint was not expensive and you can get stub rolls at
> newspapers that are many feet long.
>
> So it looks like using the big newsprint sheets and marking them
> either with magic marker (they make some with really big flat
> tips) or with several passes of india ink with something easy
> to use like a Steel Brush dip pen, is a really good way to make
> your own line patterns for robot testing.
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Message is in Reply To:
 | | Black
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| Since I am currently working on line following, I did some tests with the Lego active light sensor. I mounted one on a small test cart pointing down a bit more than 1/8 inch above the "ground". The 1.5 test pad reads white 57 black 38 green 46 I (...) (27 years ago, 28-Jan-00, to lugnet.robotics.rcx)
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