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LEGO Mindstorms NXT

- sensors and electronics

in NXT robots

Pavel Ripka, (modified by Vojtch Petrucha)

Department of Measurement, CTU in Prague

http://measure.feld.cvut.cz

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Sensors ?

Interface between a real world and

your control algorithms and artificialintelligence (robots)

A sensor is a device that measures a

physical quantity and converts it into a

signal which can be read by an

observer or by an instrument. (Wiki)a

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Whats this?

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1.5 2 billions US$ burning..

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B2 Spirit

Moisture in three of the 24 sensors that

feed information into the bombers

computer system caused the sensors to

send bad information about the planes

speed and altitude, and howfar up or

down the bombers nose was pointed.

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NXT brick

http://mindstorms.leg

o.com/Overvie

w/NXTreme.aspxhttp://www.jstuber.net/lego/nxt-programming/nxt-top_big.jpg

Main processor: Atmel 32-bit AR

M

processor, AT91SAM7S256

- 256 KB FLASH

- 64 KB RAM

- 48 MHz

Co-processor: Atmel 8-bit AVR

processor, ATmega48

- 4 KB FLASH

- 512 Byte RAM

- 8 MHz

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4input ports

1: analog input 10-bit ADC 0..5 V+ current generator (back compatibility with RCX)

2, 3: GND

4: + 4,3 V 5,6: digital I-O, I2C bus (Inter-Integrated Circuit)

(only the ultrasonic sensor uses it from the basic set..)

I2C half-duplex communication,

START,ADDRESS,ACKNOWLEDGE, DATA , STOP

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3 output ports

1-2 PWM outputs for motors (or programmable voltage 0..5 V) 3 GND

4 power supply 4,3 V

5,6 Schmitt inputs (e.g. for IRC sensor - encoder)

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Touch sensor

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measures level of soundmagnitude acoustic pressure

0 dB you can here it..

120 (130) dB level of pain

Microphone

A5M02AKA Akustick aplikace

dBa .... physiological correction

it shows percents [%] of90 dB

4-5% silent room

5-10% far conversation

10-30% normal conversation

30-100% screaming or noisy music

20 dB = one order increase

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Ultrasonic range-meter

measures distance 0 (?) to 255 centimeters with a resolution

+/- 3 cm.

principle: time offlight

piezoelectric transmitter and receiver(separated)

speed ofsound 346 m/s (changing with

temperature, pressure)

good reflection is needed

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Motor and IRC sensor

If you use the Move block in the LEGO

MINDSTORMSNXT software to program your

motors, the two motors will automatically

synchronize, so that your robot will move in a

straight line.

Rotation Sensor measures motor rotations in

degrees or full rotations [accuracy of +/- one

degree].

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motor characteristics

http://www.philohome.com/motors/motorcomp.htm

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How you can

measure the

torque


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Motor efficiency

A3B14EPR Elektrick pohony pro automatizaci a robotiku

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Overload protection ofNXT motor

current through braked motor: 2 A,

momentum 50N.cm

in-build PTC thermistor over-voltage diode (D4) .. both polarities 15 V


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Motor control H bridge

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IRC sensor

- like in a computer mouse

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counts on rising and falling edges (direction and resolution)

Non-magnetic platform, also contains IRCs. Code-wheel made ofPCB, no

ferromagnetic components..

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Simple I2C interface

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Connection ofDACand VCO for RC servo

http://www.extremenxt.com/tda8444.html

A3M38ZDS Zpracovn a digitalizace analogovch signl

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Communication

Bluetooth wireless communication

CSR BlueCoreTM 4 v2.0 +EDR System

1 master + max. 3 slave

USB 2.0 communication Full speed port

12 Mbit/s

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USB connection Control Transfer

Isochronous Transfer

Interrupt Transfer

Bulk Transfer

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BluetoothBluetooth wireless

communication CSR

BlueCoreTM 4 v2.0

+EDR System

-Supporting the Serial

Port Profile (SPP)

- Internal 47 KByte RAM

- External 8 MBit FLASH

- 26 MHz

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LCD display control

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Sound output channel with 8-bit resolution

- Supporting a sample rate of2-16 KHz

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Battery6 AA cells or Li-Ion accu

reversible fuse 1,85 A (disconnects at about 3,3 A

5 V stab. 3,3 V stab. for ARM7 a Bluecore

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Other sensors forNXT

Infrared range-meter (triangulation)

20 150 cm, resolution mmConnection I2C

Sharp GP2Y0A02YK sensor

http://www.mindsensors.com

http://www.eduxe.cz/legomenu/hitechnic_menu.htm

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detektor

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Compass

Ourwo

rk..

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Digital Camera

Ourwork

Where we teach it..: A3M38VBM L

Videometrie a bezkontaktn men

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Accelerometer

mindsensors

hitechnic

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Gyro

http://web.mac.com/ryo_watanabe

video http://www.youtube.com/watch?v=V40ScvJeFxg

Prezentace NTXway-G

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Gyroscope

(iMEMS by Analog Devices)

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Real operation

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Pressure

http://www.extremenxt.com/pressure.htm

mindsensors

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Other applications

RFID reader http://www.norgesgade14.dk/rfid.phpMicroprocesor communicates with NXT using I2C

HiTechnic Products http://www.hitechnic.com

Codatex RFID sensor http://www.codatex.com

Documents

Roboti ENG