VADCFLL-L Archives

November 2011

VADCFLL-L@LISTSERV.JMU.EDU

Options: Use Monospaced Font
Show HTML Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Anant Narayanan <[log in to unmask]>
Reply To:
Anant Narayanan <[log in to unmask]>
Date:
Thu, 10 Nov 2011 09:09:49 -0500
Content-Type:
multipart/alternative
Parts/Attachments:
text/plain (2992 bytes) , text/html (6 kB)
I do expect some interference.



Although we have not done testing with camera flashes, we tested sensor
response times a few months back while trying to debug some balky program
(when sensor based termination of an unlimited move did not work
consistently -- this is a known problem, with numerous solutions).  We
found that most of the standard Lego sensors have millisecond response
times (I even remember seeing a website where such results were posted).
These response times are consistent with duration of modern camera
flashes/strobes (same order of magnitude).



Thus if you have calibrated the sensors to distinguish light from dark (or
white from black), and then program using the same sensors (e.g. white is
anything above a threshold level), you can have situations where grey or
black can appear to be white if the ambient light level changes (such as
with a bright flash in close proximity).  I am guessing that the problem
will be minimal if the camera flash is held 10 or more feet from the table,
or if a diffuser is used.  There are also a number of light/color sensor
settings that can affect my response to your question.



Scott Evans, the FLL game designer recommends that the light sensors be
cloaked so that ambient light is blocked as much as possible -- he would
recommend a light sensor mechanical design that would let the sensor work
the same way in a coalmine or bright daylight.



Our kids have never found the time to construct good quality shielding . .
.  maybe one of these years, they reach far enough to make it worthwhile to
research/invest this technique.  Right now our teams' design philosophy is
based on design and programming simplicity -- I counsel the kids to avoid
program bloat, even if this stops them from showing off all their skills to
the robot design judges.



Best,

Nari Narayanan
*------------------------------------------------------------
Anant S Narayanan
McLean Robotics Institute
McLean VA 22102
202-421-3826 (cell)
[log in to unmask]
-----------------------------------------------------------*
On Thu, Nov 10, 2011 at 8:30 AM, Scott Rakestraw <[log in to unmask]>wrote:

> Has anyone experienced flash photography interfering with light sensors
> during a mission run?   Our team was asking this questions and I do not
> have an answer.  ****
>
> ** **
>
> Scott Rakestraw****
>
> FLL Coach****
>
> ** **
>
> ** **
>
> ** **
>
> ** **
> ------------------------------
> To UNSUBSCRIBE or CHANGE your settings, please visit
> https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or
> leave the list".
> VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L.
> Visit https://listserv.jmu.edu/archives/vadcfll-announcements-l.html to
> subscribe.




-- 
*
*

-- To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list".

-- VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-ANNOUNCEMENTS-l.html to subscribe.


ATOM RSS1 RSS2