Workshop on Microcontroller · PDF fileInterfacing Servo motor and controlling angular...

Workshop on

Designing a wireless Controlled Battlebot and it’s

transmitter via bluetooth using joystick.

Research & Training Circle

Presented By

Mohammed Abdul Kader

B.Sc. in EEE, CUET (2006-10)

Assistant Professor, Dept. of EEE, IIUC

Email:[email protected] Website: kader05cuet.wordpress.com

Workshop on "Designing Battlebot" By-Mohammaed Abdul Kader, Assistant Professor, EEE, IIUC 2

Objective

1) Designing a battlebot which has following features-

* Remote Controlled

* Can move at any direction with regulated speed

* has an arm to hit other bot.

2) Designing a transmitter using joystick and bluetooth module which has

following features-

* Can control the speed and movement of Battlebot

* Can control the movement of arm of battlebot


Session Topics

Session-1

(10 am – 1 pm)

Microcontroller, Familiarization with ARDUINO UNO and programming,

Controlling speed and direction of DC motor, Familiarization with motor driver

(L298) and Joystick, A/D conversion, Controlling DC motor by joystick,

Interfacing Servo motor and controlling angular position of servo motor by

microcontroller.

Session-2

(2 pm-5 pm)

Familiarization with HC-05 Bluetooth module, Configuring BT module by AT

command, Paring two BT modules, Design of battlebot transmitter using joystick

and Bluetooth module as master, Design of battlebot using DC motor-servo

motor and Bluetooth module as slave.

Workshop Lecture plan


Session-1

Microcontroller, Familiarization with ARDUINO UNO and programming, Controlling

speed and direction of DC motor, Familiarization with motor driver (L298) and Joystick,

A/D Conversion, Controlling DC motor by joystick, Interfacing Servo motor and

controlling angular position of servo motor by microcontroller.

Timer/ Counter

I/O Port

What is Microcontroller?

Micro-computer in a single chip.


Name of Some Microcontroller Manufacturer

ATMEL (AVR microcontroller)

Microchip (PIC microcontroller)

Texas Instruments (TI)

Freescale

Philips

Motorola ARDUINO


Crystal Oscillator Program Loader Microcontroller Linear Voltage Regulator

Advantages of Arduino: Reduces hardware complexity


Advantages of Arduino: Programming Easy

• Programming in C

• Lot of functions in the library.

• No need to learn internal

architecture of microcontroller.


Arduino UNO Digital I/O Pins

Serial

Tx-Rx Pins

Vcc and GND Pins


Digital I/O Pins

Most of the important pins of microcontroller are digital input-output pins.

These pins are used to connect INPUT Device (i.e. Push Button, keypad, digital sensors

etc) and OUTPUT Device (i.e. LED, Display, Relay, Motor etc.) with microcontroller.

These pins can act as INPUT or

OUTPUT.

Digital Output pin means microcontroller

can make this pin HIGH or LOW state

(Write Operation).

Digital Input pin means microcontroller

can read HIGH or LOW state from other

devices (Read Operation).


Configuring Digital I/O Pins

digitalWrite(pin number, HIGH/LOW)

digitalWrite(13,HIGH)

digitalWrite(13,LOW)

pinMode(pin Number, OUTPUT)

An LED is connected with pin 13.

The pin should be an OUTPUT pin.

We can configure a pin as OUTPUT by

“pinMode” function.

pinMode(13, OUTPUT)

Configuring as OUTPUT

Making a Pin HIGH or LOW

Microcontroller can make a digital pin HIGH or LOW by

digitalWrite function.


Program Structure in ARDUINO

Verify Program

Load Program

Processor run the instructions

written here only once after

loading program or reset .

Serial monitor

Processor run the instructions written here

repeatedly after loading program or reset .

i.e. void loop() function creates an infinite

loop.


void setup()

{

pinMode(13,OUTPUT);

}

void loop()

{

digitalWrite(13,HIGH);

delay(300);

digitalWrite(13,LOW);

delay(300);

}

LED Blinking

Note: To insert a time delay in the program use following function-

delay(time_in_ms);


Moving a Robocar


Direction control of DC Motor

+

-

+

-

HIGH

LOW

2.7 to 5V

0 to 0.5V

40 mA

P=VI = 5 X 40 mA = 200 mW= 0.2 W

Not enough power to drive a DC motor.

The DC motor used in our project

needs voltage of 6 to 12 V and 300-

1000 mA current. Minimum of

(6X300) =1800 mW or, 1.8 W power

So, OUTPUT pins of microcontroller can not

drive the DC motor required in our project.

How can we control the direction of DC motor

by microcontroller? Workshop on "Designing Battlebot" By-Mohammaed Abdul Kader, Assistant Professor, EEE, IIUC

15

H-Bridge Motor driver

HIGH

LOW


HIGH

LOW



LOW

HIGH

ON

ON

OFF

OFF



HIGH

LOW



Motor Driver IC (L298N)



Speed Control of DC Motor

In ARDUINO,

duty cycle of PWM is set by the function

analogWrite(pin_no, duty_cycle)

Where, duty_cycle = 0 to 255 (0 to 100%)

L298 Motor Driver Module



The joystick in the picture is nothing but two potentiometers that allow us to measure the movement

of the stick in 2-D. Potentiometers are variable resistors and, in a way, they act as sensors providing us

with a variable voltage depending on the rotation of the device around its shaft.

Joystick


A/D

Converter

D0 D1 D2 D3 D4 D5 D6 D7 D8 D9

FSR 1

FSR 2 Mult

iple

xer

S0 and S1 used for

Analog Channel

Selection S0 S1

A0

A1 Analo

g

input

Digital output

Positive ref. is 5V and

Negative ref. is 0V

i.e.Conversion range (0-5

V)

Sensor Physical

parameter A/D Converter

Converts physical parameter to

corresponding analog voltage

Converts analog voltage to

digital voltage

Microprocessor

Analyze or process the

physical parameter

A/D Converter


A/D Converter in ATmega328P (ARDUINO UNO)

• 10-bit resolution (Divide 0 to Ref Volt into 1024 levels)

• 6 channel

• Internal or, External reference selection

Function to read analog value

analogRead(pin number)

Reads the analog voltage from the specified

analog pin and returns the digital value (0 to

1023) of the analog voltage.

Syntax: analogRead(pin)


Controlling the speed and direction of DC motor by Joy-stick


Controlling the speed and direction of DC motor by Joy-stick

const int MT1=4;

const int MT2=5;

const int x_axis=A0;

const int y_axis=A1;

const int enable=9;

int x_value, y_value;

void setup()

{

pinMode (MT1, OUTPUT);

pinMode(MT2, OUTPUT);

Serial.begin(9600);

}

void loop()

{

byte duty_cycle;

x_value=analogRead(x_axis);

y_value=analogRead(y_axis);

Serial.println(x_value);

Serial.println(y_value);

delay(10);

if(x_value>600)

{

duty_cycle=map(x_value,600,1023,0,255);

analogWrite(enable,duty_cycle);

digitalWrite(MT1,HIGH);

digitalWrite(MT2,LOW);

}

else if(x_value<400)

{

duty_cycle=map(x_value,400,0,0,255);

analogWrite(enable,duty_cycle);


digitalWrite(MT2,HIGH);

}

else

{

analogWrite(enable,0);



}}

Servo motor Interface

A servo motor (or servo) is a little box that contains a DC motor, an output shaft (servo arm) which is

connected to the motor through a series of gears, and an electronic circuit to control the position of the

shaft. The objective of using a servo is to achieve precise angular positioning of an object.


How servo motor works

In order to accomplish a servo function, an instantaneous positioning information of the output shaft is

fed back to the control circuit using a transducer. A simplest way of doing this is by attaching a

potentiometer to the output shaft or somewhere in the gear train. The control electronics compares the

feedback signal (which contains the current position of the shaft) from the potentiometer to the control

input signal (which contains information of the desired position of the shaft), and any difference

between the actual and desired values (known as an error signal) is amplified and used to drive the DC

motor in a direction necessary to reduce or eliminate the error. The error is zero when the output shaft

gets to the desired position. The functioning block diagram of a typical servomotor is shown below.



#include <Servo.h>

Servo arm;

int potpin = 0;

int val;

void setup()

{

arm.attach(9);

}

void loop()

{

val = analogRead(potpin);

val = map(val, 0, 1023, 0, 180);

arm.write(val);

delay(15);

}

Controlling angular position of servo motor by potentiometer.


Session-2

Familiarization with HC-05 Bluetooth module, Configuring BT module by AT command,

Paring two BT modules, Design of battlebot transmitter using joystick and Bluetooth

module as master, Controlling DC motor by joystick, Design of battlebot using DC

motor-servo motor and Bluetooth module as slave.


• Bluetooth is a wireless technology standard for exchanging data over short distances (range of

approximately 10 meters or 32 feet) using short-wavelength UHF radio waves in the ISM band from

2.4 to 2.485 GHz from fixed and mobile devices, and building personal area networks (PANs).

Invented by telecom vendor Ericsson in 1994.

• It’s a secure protocol, and it’s perfect for short-range, low-power, low-cost, wireless transmissions

between electronic devices.

• The industrial, scientific, and medical radio band (ISM band) refers to a group of radio bands or

parts of the radio spectrum that are internationally reserved for the use of radio frequency (RF)

energy intended for scientific, medical and industrial requirements rather than for communications.

Bluetooth Communication

https://en.wikipedia.org/wiki/Wireless

https://en.wikipedia.org/wiki/UHF

https://en.wikipedia.org/wiki/Radio_waves



https://en.wikipedia.org/wiki/ISM_band



https://en.wikipedia.org/wiki/Personal_area_network





https://en.wikipedia.org/wiki/Ericsson


Serial Communication Protocol (UART)

Baud rate: The term baud rate is used to denote the number of bits transferred per second

[bps].


Pairing two Bluetooth Modules

Steps

Step-1: Loading program and setting serial Monitor.

Step-2: Connection of BT module with ARDUINO.

Step-3: Setting at AT mode.

Step-4: Configuring Bluetooth module by AT command mode.


a) Load a blank sketch to ARDUINO board.

b) Open the serial monitor. The bluetooth module is communicating at a baud rate of 38400 in

AT command mode. So change the baud rate to 38400 at bottom right corner of the serial

monitor. Also change "no line ending " to "both NL & CR" found just beside the baud rate.

Pairing two Bluetooth Modules (Cont.)

Step-1: Loading program and setting serial Monitor.



Step-2: Connection of BT module with ARDUINO.


Step-4: Configuring Bluetooth Module by AT command

For HC05: Type "AT" (without the quotes) on the serial monitor and press enter. if "OK" appears

then everything is all right and the module is ready to take command. Now you can change the name

of the module, retrieve address or version or even reset to factory settings. To see the default name,

type AT+NAME. The name will be prompted, by default it is HC-05 or JY_MCU or something like

that. To change the name just type AT+NAME=your desired name.


Step-3: Setting at AT mode.

Press the reset button of BT Module and then connect the module with power. The module will

enter into AT command mode, A blink at every 2 sec represent that the module is in AT command

mode.


Most useful AT commands are

AT : Ceck the connection.

AT+NAME : See default name

AT+ADDR : see default address

AT+VERSION : See version

AT+UART : See baudrate

AT+ROLE: See role of bt module(1=master/0=slave)

AT+RESET : Reset and exit AT mode

AT+ORGL : Restore factory settings

AT+PSWD: see default password

To check status:

AT+COMMAND?

To set value:

AT+COMMAND= value

Here is an important note, if the key pin is not high, i.e. not connected to Vcc while receiving AT

commands(if you released it after the module entered AT mode), it will not show the default name

even after giving right command. But you can still change the name by the command mentioned

above. To verify if the name has really changed, search the device from your pc/mobile. The changed

name will appear. To change baud rate, type AT+UART=desired baud rate. Exit by sending

AT+RESET command.


Step-4: Configuring Bluetooth Module by AT command (Cont.)


AT+ROLE=0 (Slave mode)

AT+ADDR? (Find address of slave)-Copy address, change all colons (: ) by comma (,)

Change Role to Master: AT+ROLE=1 (Master Mode)

Change Connection Mode: AT+CMODE=0 (Connect to one device only) [N.B. AT+CMODE=1,

indicates the device can be connected to any device]

Bind to slave module: AT+BIND= slave address (address of the slave copied during configuring slave)


Step-4: Configuring Bluetooth Module by AT command (Cont.)

Configuring Slave

Configuring Master


Circuit Diagram of Transmitter


int x_value=0, y_value=0;

int arm_state=0;

const int buttonPin=8;

int servo=0;

void setup() {

// put your setup code here, to run once:

Serial.begin(9600);

}

void loop() {

// put your main code here, to run repeatedly:

servo=analogRead(A2);

servo=map(servo,0,1023,0,250);

if(servo>115 && servo<130) servo=120;

x_value=analogRead(A0);

y_value=analogRead(A1);

x_value=map(x_value,0,1023,0,250);

y_value=map(y_value,0,1023,0,250);

//Serial.println(x_value);

//Serial.println(y_value);

Serial.write(255);

delay(10);

Serial.write(x_value);

Serial.write(y_value);

Serial.write(servo);

}

Transmitter Program


Circuit Diagram of Receiver


Battleboat Program (Receiver Program)

#include <Servo.h>

Servo armServo;

const int rmp= A0;

const int rmn=A1;

const int lmp=A2;

const int lmn=A3;

const int ren=3;

const int len=5;

int value, x_value,y_value, rmspeed=0,lmspeed=0,

arm_state=0;

int jstick[3];

boolean a=0;

void setup(){

pinMode(rmp, OUTPUT);

pinMode(rmn, OUTPUT);

pinMode(lmp, OUTPUT);

pinMode(lmn, OUTPUT);

pinMode(ren,OUTPUT);

pinMode(len, OUTPUT);

armServo.attach(9);

Serial.begin(9600); }

void loop()

{

if(Serial.available()>0)

{

int i=0;

value=Serial.read();

if(value=255) a=1;

while(a)

{

if(Serial.available())

{

jstick[i]=Serial.read();

i++;

if(i>2) a=0;

}

}

x_value=jstick[0];

y_value=jstick[1];

arm_state=jstick[2];

}


Serial.println(arm_state);

armServo.write(arm_state);

if(y_value < 110)

{

digitalWrite(rmp,HIGH);

digitalWrite(rmn,LOW);

digitalWrite(lmp,HIGH);

digitalWrite(lmn,LOW);

rmspeed=110-y_value;

rmspeed=map(rmspeed, 0, 110, 0, 255);

lmspeed=110-y_value;

lmspeed=map(lmspeed, 0, 110, 0, 255);

//Serial.println("Reverse");

}

else if(y_value>140)

{

digitalWrite(rmp,LOW);

digitalWrite(rmn,HIGH);

digitalWrite(lmp,LOW);

digitalWrite(lmn,HIGH);

rmspeed=map(y_value, 140, 255, 0, 255);

lmspeed=map(y_value, 140,255,0,255);

}

else

{

//Serial.println("Stop");

lmspeed=0;

rmspeed=0;

}

if(x_value < 110)

{

x_value=120-x_value;

x_value=map(x_value, 0, 110, 0, 255);

rmspeed=rmspeed-x_value;

lmspeed=lmspeed+x_value;

if(rmspeed<0) rmspeed=0;

if(lmspeed>255) lmspeed=255;

}


else if(x_value>140)

{

x_value=map(x_value, 140, 255, 0, 255);

rmspeed=rmspeed+x_value;

lmspeed=lmspeed-x_value;

if(lmspeed<0) lmspeed=0;

if(rmspeed>255) rmspeed=255;

}

// to prevent buzzing

if(lmspeed<10) lmspeed=0;

if(rmspeed<10) rmspeed=0;

//Serial.println(rmspeed);

//Serial.println(lmspeed);

analogWrite(ren,rmspeed);

analogWrite(len,lmspeed);

delay(10);

}

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