Transcript Getting Started with the: Wind Energy Challenge

Microcontroller Hands-on
Workshop #3
Ahmad Manshad
New Mexico State University
Institute of Electrical and Electronics Engineers
November 7, 2009
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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Today’s 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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1
3
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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-freeduino-
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?
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