100F10_NXT and Sensors

100F10_NXT and Sensors - The Lego NXT Controller &...

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The Lego NXT Controller & Sensors September 24, 2010 Instructor: Kevin Calabro E-mail: kcalabro@umd.edu
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The control of electro- mechanical devices that can perform autonomous or preprogrammed tasks. Robotics MOTIVATION
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Outline Hardware The Lego NXT Lego Sensors Homebuilt sensors/actuators Software RobotC Programming Pseudocode Applications Robotics Hovercraft OVERVIEW
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The Lego NXT Microprocessor HARDWARE 4 Input Ports (1,2,3,4) 5V Digital Voltmeter Across Pin #1 and Pin #2 Sensors for feedback 3 Output Ports (A,B,C) Power limited (0.7A at 9V) Actuators for control Servos, relays, transistors Programmable RobotC, Robolab, NXC, BrixC, leJOS NXJ
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Input Ports – The RJ12 Connector HARDWARE “RJ12” Connector 1 2 3 4 5 6 Analog Input Ground Common Ground 4.3V output supply Digital pin to ARM 7 processor Digital pin to ARM 7 processor
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Input Ports – Analog Input Circuitry HARDWARE 5V 10k NXT Input Port Internal Circuitry + V port - Pin #1 Pin #2 or #3
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Output Ports – The RJ12 Connector HARDWARE 1 2 3 4 5 6 Pins #1 and #2 carry a pulse-width modulated output signal (square wave) Common Ground 4.3V output supply Input signal to ARM 7 processor Input signal to ARM 7 processor WARNING: Output A works differently than Outputs B and C
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Output Ports – Pulse Width Modulation HARDWARE The NXT reduces power not by reducing dc output voltage, but rather by turning the output voltage on and off periodically Upper curve is Level 50 Lower curve is Level 13 Frequency ~8000 Hz; Period ~0.125 ms Peak voltage 7-8 V
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Output Ports – Motor Controls HARDWARE Three independently-controlled outputs Designed to power small motors / servos Up to 700 mA, 7-8 V Hundreds of power settings: Level 100 Level 50 Level 0 Level -50 Full power ½ power 0 power ½ power (reversed) Duty Factor (DF): The fraction of the time in each period that the system is in the “on” or “active” state Level 100 Level 50 Level 0 Level -50 100% DF 50% DF 0% DF 50% DF
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Operation of Ports B & C HARDWARE 1 2 Forward Motor Control PWM Signal 0 Volts (ground) 0 V 1 2
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This note was uploaded on 10/05/2010 for the course ENES 100 taught by Professor Jacob during the Spring '08 term at Maryland.

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100F10_NXT and Sensors - The Lego NXT Controller &...

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