This document summarizes Day 2 of an Arduino robotics workshop. It discusses varying the speed of motors using PWM, playing tones on a buzzer, using infrared (IR) sensors to detect obstacles and teach the robot to avoid strangers, and introducing more advanced concepts like using interrupts and timer libraries to make the robot autonomous. Code examples are provided to demonstrate different techniques like reading sensor values without delays, controlling motors with interrupts, and implementing software interrupts on any pin. The document concludes by suggesting additional robotics projects and listing relevant links.

1. Arduino Robotics Workshop
Day 2
Sudar Muthu (@sudarmuthu)
http://hardwarefun.com/arduino-workshop
http://github.com/sudar

2. What we have seen so far?
Basics of Robotics
Using Breadboard
Digital and Analog I/P and O/P
Serial Communication
Controlling DC Motors
Assembled the robot
Made it run
http://hardwarefun.com 2

3. Today we will see..
Varying the speed of the motor
Play some tunes using the buzzer
How IR works
Making use of IR to find obstacles
Make the bot avoid strangers
Making it autonomous
Some Advanced stuff
http://hardwarefun.com 3

4. Varying the speed of the motor
using PWM
http://hardwarefun.com 4

5. Playing tones in the buzzer
http://hardwarefun.com 5

6. Playing sound
We can generate a square wave at specified frequency
using tone() function
Usage:
tone(pin, frequency, duration)
http://hardwarefun.com 6

7. Teaching robot to avoid strangers
Two IR LED’s. One receiver, one transmitter
Both face the same direction
Keep transmitting IR waves
If receiver receives waves, then there is a obstacle
Otherwise keep moving

8. Let’s see some code
http://hardwarefun.com 8

9. Let’s get some food 
http://hardwarefun.com 9

10. What are the limitations that
we have faced so far?
http://hardwarefun.com 10

11. Using Delay
http://hardwarefun.com 11

12. Issues with delay
Your microcontroller is going to sleep
You can’t read or write while in delay
Eg: You can’t detect an obstacle when the bot is
making a turn
http://hardwarefun.com 12

13. How to fix it?
http://hardwarefun.com 13

14. Using Timer library
https://github.com/JChristensen/Timer
http://hardwarefun.com 14

15. If we don’t read the pin, then
we miss the value
http://hardwarefun.com 15

16. Methods in Timer library
every(long period, callback);
after(long duration, callback);
oscillate(int pin, long period, int startingValue);
pulse(int pin, long period, int startingValue);
update();
http://hardwarefun.com 16

17. Interrupts
http://hardwarefun.com 17

18. Hardware support
Pin 2 and 3
Supports LOW, CHANGE, RISING, FALLING
No software support is needed
Can be removed as well
http://hardwarefun.com 18

19. Let’s see some code
http://hardwarefun.com 19

20. What if we need it on other
pins?
http://hardwarefun.com 20

21. Software Interrupts
http://code.google.com/p/arduino-pinchangeint/
http://hardwarefun.com 21

22. Can be used on any pin
http://hardwarefun.com 22

23. Let’s see some code
http://hardwarefun.com 23

24. Some ideas to try
Making your robot follow a line
Making your robot stay in a table
Replace IR with ultrasound sensor
Control the bot remotely using RF
http://hardwarefun.com 24

25. Things I have tried
Controlled it using Android phone
Controlled it using JavaScript and WebSockets
Controlled it using Bluetooth
Controlled it using RF
Added a missile launcher to it
https://github.com/sudar
http://hardwarefun.com 25

26. Links
 Arduino – http://arduino.cc
 Asimi – A simple bot using Arduino
http://hardwarefun.com/project/asimi
 Getting started with hardware programming
http://hardwarefun.com/tutorials/getting-started-with-
hardware-programming
 Getting started with Arduino
http://hardwarefun.com/tutorials/getting-started-with-
arduino-and-avr

27. Questions
Thank You
Sudar Muthu (@sudarmuthu)
http://hardwarefun.com/arduino-workshop
https://github.com/sudar/arduino-robotics-workshop