To LUGNET HomepageTo LUGNET News HomepageTo LUGNET Guide Homepage
 Help on Searching
 
Post new message to lugnet.robotics.nxtOpen lugnet.robotics.nxt in your NNTP NewsreaderTo LUGNET News Traffic PageSign In (Members)
 Robotics / NXT / 269
268  |  270
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: 
12862 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 (...) (17 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 (...) (17 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? (...) (17 years ago, 16-Dec-06, to lugnet.robotics.nxt)

7 Messages in This Thread:


Entire Thread on One Page:
Nested:  All | Brief | Compact | Dots
Linear:  All | Brief | Compact

This Message and its Replies on One Page:
Nested:  All | Brief | Compact | Dots
Linear:  All | Brief | Compact
    

Custom Search

©2005 LUGNET. All rights reserved. - hosted by steinbruch.info GbR