Ambient TOUCH LIGHT Manual do Utilizador descarregar pdf (Página 6)

ROBOTC

Sensing

Forward Until Dark / Light • 6

Carnegie Mellon Robotics Academy / For use with LEGO

MINDSTORMS® Education NXT software and base set 9797

4. A fair place to set the cutoff line is right in the middle between these two values. That would be

the average of these two values.

Forward until Dark Thresholds 201 (cont.)

2a. Place robot over dark surface

Position the robot so that the light sensor

shines on a dark-colored line.

2b. Record ”dark” sensor value

On a separate sheet of paper, write down

the Light Sensor value for a “dark” surface.

3. Now, place the light sensor over a part of the dark line, and record that reading.

value 1 + value 2

Threshold Value=

4a. Add “light” and “dark” values

The rst step in nding an average is to nd

the sum of the two values.

4b. Divide sum by 2

Since there were two values (light and dark),

divide the sum by 2 to nd the average.

4c. Write down Threshold value

This average is fairly situated, exactly

between the other two values. Record this

End of Section

With the threshold set at the point indicated by the red line, the world of light sensor readings

can now be divided into two categories: “light” values above the threshold, and “dark” values

below the threshold. This distinction will allow your robot to nd the line, by looking for the “dark”

surface on the ground.

The threshold you have calculated marks the cutoff line for your lighting conditions. Any sensor

values above the threshold value will now be considered light, and any below it will be

considered dark.

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