LEGO Mindstorms NxT 53788 User Manual - Page 25

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NXT TECHNOLOGY

ULTRASONIC SENSOR

The Ultrasonic Sensor is the other sensor that gives

your robot vision. The Ultrasonic Sensor enables the

robot to see and detect objects. You can also use it to

make your robot avoid obstacles, sense and measure

distance, and detect movement.

The Ultrasonic Sensor measures distance in

centimeters and in inches on the NXT. It is able to

measure distances from 0 to 255 centimeters with a

precision of +/-3 cm.

The Ultrasonic Sensor uses the same scientiﬁ c principle as bats: it measures

distance by calculating the time it takes for a sound wave to hit an object and return

– just like an echo.

Large-sized objects with hard surfaces return the best readings. Objects made of

soft fabric or that are curved (like a ball) or are very thin or small can be difﬁ cult for

the sensor to detect.

Note that two or more Ultrasonic Sensors operating in the same room may interfere

with each other's readings.

Test it!

Test the Ultrasonic Sensor's ability to measure distance:

Connect the Ultrasonic Sensor to the NXT.

Select the View submenu in the NXT display.

Select the Ultrasonic Sensor icon

and the port where you've con-

nected the sensor.

Select the Try Me submenu on the NXT's display and test your

Ultrasonic Sensor. You'll get a fun reaction.

Measure the distance to an object. For example, move your hand closer to

the sensor and watch the readings change.

Suggestions for use

You can use the Ultrasonic Sensor in

many different ways. Program a robot to

sneak around the house without it

bumping into things. Or make an

advanced burglar alarm robot that reacts

to movement as well as light. Your

Scorpion robot "stings" if you come to

close.