Getting Started with the: Wind Energy Challenge

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Microcontroller Hands-on Workshop 3
Ahmad Manshad New Mexico State University Institut
e of Electrical and Electronics
Engineers November 7, 2009
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Agenda for Today

• Quick Review
• More sensors (Infrared)
• Introduction to pulse width modulation (PWM)
• Controlling motors with the Arduino
• Begin working on robot

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Todays Kit

1. Arduino Microcontroller/ USB Cable
2. Breadboard
3. 1x Red LED
4. Infrared Sensor
5. Wires
6. Soldering Iron w/ solder
7. Freeduino Motor Controller

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Quick Review - Code

• int ledPin 13 // LED connected
  to digital pin 13
•  
• void setup()
• pinMode(ledPin, OUTPUT) // sets the
  digital pin as output
•  
• void loop()
• digitalWrite(ledPin, HIGH) // sets the LED
  on
• delay(1000) // waits for a
  second
• digitalWrite(ledPin, LOW) // sets the LED
  off
• delay(1000) // waits for a
  second
•  

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Quick Review - Breadboard
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Infrared Proximity Sensor

• Send infrared light through IR-LEDs, which is
  then reflected by any object in front of the
  sensor.

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Infrared Proximity Sensor

• Sender IR Emitter LED
• Receiver IR Detector LED w/ an operational
  amplifier.

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Solder Wires to IR Sensor

• Left pin (1) SIGNAL
• Middle pin (2) GROUND
• Right pin (3) POWER( 5 volts)

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3
1
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How to Solder Wires to IR Sensor

1. Warm up the iron
2. Prepare a moisten sponge
3. Apply heat to the lead.
4. Apply solder to the lead
5. Allow solder to cool down
6. Inspect the connection

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IR connected to arduino - CODE
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Pulse Width Modulation

• PWM signal is a digital square wave where the
  fraction of the time the signal is on can be
  varied between 0 and 100.
• Call analogWrite(pin, dutyCycle), where dutyCycle
  is a value from 0 to 255.
• Use one of the PWM pins (3, 5, 6, 9, 10, or 11).

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Applications of Pulse Width Modulation

• Dimming an LED
• Generating audio signals.
• Generating a modulated signal, for example to
  drive an infrared LED for a remote control.
• Providing variable speed control for motors.

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Motors

• Electromechanical device that converts electrical
  energy to mechanical energy

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Motors!

• DC Motor
• Servo Motors
• Stepper Motor

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DC Motor

• Pros
• Simple cheap (only 2 wires)
• Fast can be geared down for higher torque
• Easy to reverse
• Speed control through PWM
• Cons
• No built-in feedback

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Servo Motor (DC motor w/ feedback)

• Pros
• Simple (3 wire) and Standard
• accurate even under load
• High torque
• Cons
• Slower
• More expensive

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Servo Motor
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Simple Motor Driver

• Motors are inductive loads and require a high
  current
• Use a transistor to switch the high-current load

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H-Bridge

• An H-bridge is an electronic circuit which
  enables a voltage to be applied across a load in
  either direction.
• Often used in robotics and other applications to
  allow DC motors to run forwards and backwards.
• H-bridges are available as integrated circuits,
  or can be built from discrete components (i.e.
  four switches)

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H-Bridge

• S1 and S4 closed - positive voltage applied
  across the motor.
• S2 and S3 closed - voltage is reversed, negative
  voltage applied.
• S1 and S2 (or S3 and S4) closed short circuit!

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Freeduino Motor Controller

• Control 2 motors from your Arduino
• SN754410NE motor driver

• Board and Arduino pinout
• Motor A Direction - Arduino Digital pin 13
• Motor A Speed (PWM) - Arduino Digital pin 10
• Motor B Direction - Arduino Digital pin 12
• Motor B Speed (PWM) - Arduino Digital pin 9

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Assembling Freeduino Motor Controller

• GO TO WWW.GOOGLE.COM
• TYPE FREEDUINO MOTOR
• CLICK ON THE FIRST LINK
• CLICK THE LINK THIS GUIDE
• Or Type the following in the address bar
• http//mcukits.com/2009/03/12/assembling-the-freed
  uino-arduino-motor-shield/

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Soldering Components to PCB
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Robot Design

• Discuss Robot Plans with Team Members!

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Questions or Comments?