Microcontroller Hands-on Workshop #3 Ahmad Manshad New Mexico State University Institute of Electrical and Electronics Engineers November 7, 2009

2 Agenda for Today  Quick Review  More sensors (Infrared)  Introduction to pulse width modulation (PWM)  Controlling motors with the Arduino  Begin working on robot

3 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

4 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 }

5 Quick Review - Breadboard

6 Infrared Proximity Sensor  Send infrared light through IR-LEDs, which is then reflected by any object in front of the sensor.

7 Infrared Proximity Sensor  Sender: IR Emitter LED  Receiver: IR Detector LED w/ an operational amplifier.

8 Solder Wires to IR Sensor  Left pin (1) – SIGNAL  Middle pin (2) – GROUND  Right pin (3) – POWER( +5 volts) 1 2 3

9 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

10 IR connected to arduino - CODE

11 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).

12 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.

13 Motors Electromechanical device that converts electrical energy to mechanical energy

14 Motors! DC Motor Servo Motors Stepper Motor

15 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

16 Servo Motor (DC motor w/ feedback) Pros Simple (3 wire) and “Standard” accurate even under load High torque Cons Slower More expensive

17 Servo Motor

18 Simple Motor Driver Motors are inductive loads and require a high current Use a transistor to switch the high-current load

19 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)

20 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!

21 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

22 Assembling Freeduino Motor Controller GO TO: TYPE: FREEDUINO MOTOR CLICK ON THE FIRST LINK CLICK THE LINK: “THIS GUIDE” Or Type the following in the address bar: arduino-motor-shield/

23 Soldering Components to PCB

24 Robot Design  Discuss Robot Plans with Team Members!

25 Questions or Comments?