Subject:
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Re: Has anyone figured out how to improve the NXT light sensor?
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Mon, 18 Dec 2006 00:00:57 GMT
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Reply-To:
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Geoffrey Hyde <gdothyde@STOPSPAMbigponddotnetdotau>
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Viewed:
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12776 times
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"Philippe Hurbain" <philohome@free.fr> wrote in message
news:JAF8tF.16H@lugnet.com...
> Hello Geoffrey,
>
> > 2. I was wondering if the light could be piped uisng some sort of
> > fiber-optic cable method - this presumably would mean shielding the light
> > LED in some kind of sheath which would considerably narrow it. I've no
> > idea
> > how hot the LED can get during operation, so presumably the sheath would
> > have to be able to withstand a moderate temperature rise without melting
> > or
> > smoking.
>
> First, don't worry about heat - such leds are really cool (thermically
> wise)
> devices! This one dissipates only about 20 mW...
That's good to hear.
> Your fiber optic cable idea is interesting... and it works well!
I'll have to download and check out your program. It looks great! I'll
also have to see if I can get the sensor to detect 1x1 plates - I like
working with big challenges in small sizes! ;-) It probably should detect
them from above at the very least.
But first there's the slight additional challenge of building the model in
studless so I can get 1 or at the most 2 stacked together - they tend to do
that sometimes in the hopper - in front of the sensor so I can tell if it's
going to successfully measure it or not.
> I used the fiber optic cable included for VLL stuff in RIS 2.0 kit
> (similar ones
> are also available in some ExoForce sets). The fiber is maintained in
> front of
> the LED and the other end is routed to face the sensor.
> See http://www.brickshelf.com/gallery/Philo/LightBarrier/lb1.jpg and
> http://www.brickshelf.com/gallery/Philo/LightBarrier/lb2.jpg
Your BrickShelf gallery has plenty of good building techniques. ;-)
> In order to try this setup, I use it to count soccer balls that are
> notoriously
> hard to detect because of the black dots on white background. Here is the
> assembly http://www.brickshelf.com/gallery/Philo/LightBarrier/lb3.jpg, and
> simple NXT-G program:
> http://www.brickshelf.com/gallery/Philo/LightBarrier/ballcount.rbt
By the way, is the reddish-pink hue just a camera side-effect, or did that
come about because the light doesn't travel perfectly through the fiber
optic cable? Or is it because of the orange background of the light sensor
itself?
> With a slightly improved program
> (http://www.brickshelf.com/gallery/Philo/LightBarrier/ballcount2.rbt) it
> is able
> to properly detect and count several nearby balls:
> http://www.brickshelf.com/gallery/Philo/LightBarrier/lb4.jpg
>
> Of course, if you use this contraption in bright ambient light, you must
> shield
> it properly!
Yup, I figure it's going to need quite a bit of shielding for it to get
working fairly well.
Many thanks for the contraption, and for some ideas I might be able to use
from your BrickShelf folder.
I'll have to give you a credit line! Please let me know if I forget! ;-)
Cheers ...
Geoffrey Hyde
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