Optical Sensor Questions

[PyroPhin]

been playing with the Edubot and the optical sensors in this years kit at home for the past couple of days.. and i noticed someting a little pecular about them.

they will sense other surfaces then Retroreflective tape.. i hold my hand in front of them and thet trigger. also.. i built a model of the sensor array we plan for the bot this year and im finding out that the sensors have a hard time tracking white on red. im using construction paper, but i dont have any carpet.
anyone else encounter this problem or a simalar one?

the other thing is.. that im not totally shure about the tracking lines on the field this year, are they made with retroreflective tape or is it just a strip of white duct tape

~Pyro

[Bduggan04]

It's actually more of a cloth tape. The reason for this is that it stretches to make the 4' radius better. The sensors don't require retroreflective tape, they can also detect differences between light and dark.

[Adam Shapiro]

they will sense other surfaces then Retroreflective tape..

The sensors sense an infrared beam that they emit. The infrared will reflect off other surfaces though different surfaces will work better or worse. You probably noticed that when you use your hand, it has to be quite close to sense it...

are they made with retroreflective tape or is it just a strip of white duct tape

The white lines are made with vinyl tape that is 2" thick. The actual tape used is Shurtape, PC-628 Premium Grade Tape, Vinyl Coated Cloth, White, 2" Wide that can be purchased at www.tapemonster.com. See section 10.4 in the "Game" section in the manual (http://www2.usfirst.org/2003comp/The_Game.pdf).

[Aashish]

you can also adjust the the little screw on the back of the sensor to decrease or increase the difference between white and dark or other colors

just play around with the screw on the back

[Team852 (DB)]

Team 852 has had the same problem.

I believe that the sensors emit and track red light (low frequency within the visible spectrum), not infrared. I still need to look at the charts they sent us.

Red light emitted from the sensor reflects very well off of red paper (Red paper is red because it reflects red light, and absorbs a good bit of the other frequencies).

We have not tried it on red carpet, and wonder if anyone else has made such an attempt. Of course, if so, what were the results?

-DB, The Athenian Robotics Collective