NXT Sensors

NXT Sensors

The NXT

The NXT is the brain of a MINDSTORMS® robot. It’s an intelligent, computer-controlled LEGO® brick that lets a MINDSTORMS robot come alive and perform different operations.

Motor Ports
The NXT has three output ports for attaching motors - Ports A, B and C

Sensor Ports
The NXT has four input ports for attaching sensors - Ports 1, 2, 3 and 4.

USB Port
Connect a USB cable to the USB port and download programs from your computer to the NXT (or upload data from the robot to your computer). You can also use the wireless Bluetooth connection for uploading and downloading.

Loudspeaker
Make a program with real sounds and listen to them when you run the program.

NXT Buttons
Orange button : On / Enter / Run
Light grey arrows: Used for moving left and right in the NXT menu
Dark grey button: Clear / Go back

NXT Display
Your NXT comes with many display features - see the MINDSTORMS NXT Users Guide that comes with your NXT kit for specific information on display icons and options.

Technical Specifications

32-bit ARM7 microcontroller

256 Kbytes FLASH, 64 Kbytes RAM

8-bit AVR microcontroller

4 Kbytes FLASH, 512 Byte RAM

Bluetooth wireless communication (Bluetooth Class II V2.0 compliant)

USB full speed port (12 Mbit/s)

4 input ports, 6-wire cable digital platform (One port includes a IEC 61158 Type 4/EN 50 170 compliant expansion port for future use)

3 output ports, 6-wire cable digital platform

100 x 64 pixel LCD graphical display

Loudspeaker - 8 kHz sound quality. Sound channel with 8-bit resolution and 2-16 KHz sample rate.

Power source: 6 AA batteries

Suggestions for Use
You can use the touch Sensor to make your robot pick up things: a robotic arm equipped with a Touch Sensor lets the robot know whether or not there is something in its arm to grab. Or you can use a Touch Sensor to make your robot act on a command. For example, by pressing the Touch Sensor you can make your robot walk, talk, close a door, or turn on your TV.

Touch Sensor

The Touch Sensor gives your robot a sense of touch. The Touch Sensor detects when it is being pressed by something and when it is released again.

Suggestions for Use
You can use the touch Sensor to make your robot pick up things: a robotic arm equipped with a Touch Sensor lets the robot know whether or not there is something in its arm to grab. Or you can use a Touch Sensor to make your robot act on a command. For example, by pressing the Touch Sensor you can make your robot walk, talk, close a door, or turn on your TV.

Sound Sensor

The Sound Sensor can detect both decibels [dB] and adjusted decibel [dBA]. A decibel is a measurement of sound pressure.

dBA: in detecting adjusted decibels, the sensitivity of the sensor is adapted to the sensitivity of the human ear. In other words, these are the sounds that your ears are able to hear.

dB: in detecting standard [unadjusted] decibels, all sounds are measured with equal sensitivity. Thus, these sounds may include some that are too high or too low for the human ear to hear.

The Sound Sensor can measure sound pressure levels up to 90 dB – about the level of a lawnmower. Sound pressure levels are extremely complicated, so the Sound Sensor readings on the MINDSTORMS NXT are displayed in percent [%]. The lower the percent the quieter the sound. For example:

4-5% is like a silent living room

5-10% would be someone talking some distance away

10-30% is normal conversation close to the sensor or music played at a normal level

30-100% are people shouting or music being played at a high volume

Light Sensor

The Light Sensor is one of the two sensors that give your robot vision [The Ultrasonic Sensor is the other]. The Light Sensor enables your robot to distinguish between light and dark. It can read the light intensity in a room and measure the light intensity of colored surfaces.

Suggestions for Use
You can use the Light Sensor to make a burglar alarm robot: when an intruder turns on the light in your room the robot can react to defend your property. You can also use the Light Sensor to make a line-following robot or a robot that can sort things by color.

Ultrasonic Sensor

The Ultrasonic Sensor is one of the two sensors that give your robot vision [The Light Sensor is the other]. The Ultrasonic Sensor enables your 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. It is able to measure distances from 0 to 255 centimeters with a precision of +/- 3 cm.

The Ultrasonic Sensor uses the same scientific 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 difficult for the sensor to detect.

* Note that two or more Ultrasonic Sensors operating in the same room may interrupt each other’s readings.

Servo Motors

The three Servo Motors give your robot the ability to move. If you use the Move block in the LEGO MINDSTORMS NXT software to program your motors, the two motors will automatically synchronize, so that your robot will move in a straight line.

Built-in Rotation Sensor

Each motor has a built-in Rotation Sensor. This lets your control your robot’s movements precisely. The Rotation Sensor measures motor rotations in degrees or full rotations [accuracy of +/- one degree]. One rotation is equal to 360 degrees, so if you set a motor to turn 180 degrees, its output shaft will make half a turn.

The built-in Rotation Sensor in each motor also lets you set different speeds for your motors [by setting different power parameters in the software]. Try running the motors at different speeds.