IR Detection Issues

smelliott

My friends and I have been playing around with a Boe-Bot and are currently having trouble getting the IR detectors to differentiate between white and black lines. Is there anyone who can give us some advice on this issue?

Franklin

You could use white light and phototransistors or make sure your black is really "black" to IR wavelengths.

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- Stephen

smelliott

Thank you, your help is appreciated; though not quite understood...

Steph Lindsay

Hi Smelliott,

The infrared line following works because most black surfaces absorb infrared light and white surfaces reflect it. HOWEVER, if you have printed black·areas with a printer that can also be used to print digital photos, that black ink happens to be very reflective of infrared, almost as reflective as the white paper.· We find that most brands of black electrical tape, black Sharpie pen, and black laser copier toner all absorb infrared.·Black rubber·wall base also absorbs infrared, and different brands of black construction paper will vary - some are quite shiny.

Are your friends going through Chapter 7 of Robotics with the Boe-Bot step by step?· If they have had success with Activity #3, Infrared Detection Range Adjustments, they can be sure the IR sees a white piece of paper at a given distance.· Now, try using a large piece of your black material to make sure it is invisible to the infrared at the same distance.

If you are using the IR components plugged directly into the breadboard and trying to do line-following, you will have to use very wide black lines since the emitter and detector are far away from the surface.· Notice that in Chapter 7, Activity 6 the simulated drop-off detector setup uses three rows of electrical tape.·

If your friends want a more efficient line-follower setup, this kit works well even with a single strip of electrical tape for a line, because it places the IR emitters and sensors right above the surface:

http://www.parallax.com/Store/Robots/RoboticAccessories/tabid/145/CategoryID/22/List/0/SortField/0/Level/a/ProductID/77/Default.aspx

-Stephanie Lindsay

Parallax Inc.

smelliott

Thank you - yes we have been going through the book; though, your comments were more than perfectly helpful, that had actually been the problem, the surface used and such. Thanks