NXT programmable brick : 269


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Subject:	Re: Has anyone figured out how to improve the NXT light sensor?
Newsgroups:	lugnet.robotics.nxt
Date:	Sun, 17 Dec 2006 14:12:51 GMT
Viewed:	13482 times

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... Your fiber optic cable idea is interesting... and it works well! 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 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 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! Cheers, Philo

Message has 2 Replies:

		Re: Has anyone figured out how to improve the NXT light sensor?
"Philippe Hurbain" <philohome@free.fr> wrote in message news:JAF8tF.16H@lugnet.com... (...) That's good to hear. (...) 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 (...) (18 years ago, 18-Dec-06, to lugnet.robotics.nxt)

		Re: Has anyone figured out how to improve the NXT light sensor?
(...) I've also used this the other way around, using a fiber optic cable to route light to the phototransistor itself. Do this with more than one light sensor, and you can have much better spatial resolution (the ends of two fiber optic cables can (...) (18 years ago, 18-Dec-06, to lugnet.robotics.nxt)

Message is in Reply To:

		Has anyone figured out how to improve the NXT light sensor?
I'm looking for ways to build this sensor into a studless beam project of mine, and I was wondering, given it's large size and the comparative brightness of the LED used to light it, how can I use it to detect if an object is blocking a path? (...) (18 years ago, 16-Dec-06, to lugnet.robotics.nxt)

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