Download Table showing DTMF Low and High frequency tones and decoded

MOBILE CONTROLLED ROBOT
INTRODUCTION:
DTMF Mobile controlled ROBOT is a machine that can be
controlled with a mobile. In this project, the robot is controlled by a mobile
phone that makes a call to the mobile phone attached to the robot. In the
course of a call, if any button is pressed, a tone corresponding to the button
pressed is heard at the other end of the call. This tone is called "Dual Tone
Multiple-Frequency" (DTMF) tone. The robot perceives this DTMF tone with
the help of the phone stacked on the robot. The received tone is processed
by the microcontroller with the help of DTMF decoder. The microcontroller
then transmits the signal to the motor driver ICs to operate the motors & the
robot moves accordingly. Use of a mobile phone for robotic control can
overcome these limitations. It provides working range as large as the
coverage area of the service provider.
DTMF Technology:
DTMF stands for Dual Tone - Multi Frequency and it is the basis for
telephone system. DTMF is the generic term for Touch-Tone.Dual-tone
multi-frequency (DTMF) signaling is used for telecommunication signaling
over analog telephone lines in the voice-frequency band between
telephone handsets and other communications devices and the switching
center.
The DTMF telephone keypad is laid out in a 4×4 matrix of push
buttons in which each row represents the low frequency component and
each column represents the high frequency component of the DTMF signal.
Pressing a key sends a combination of the row and column frequencies.
For example, the key 1 produces a superimposition of tones of 697 and
1209 hertz (Hz). Initial pushbutton designs employed levers, so that each
button activated two contacts. The tones are decoded by the switching
center to determine the keys pressed by the user.DTMF tones are able to
represent one of the 16 different states or symbols on the keypad. This is
equivalent to 4 bits of data, also known as nibble.
Table showing DTMF Low and High frequency tones and decoded output:
MT8870 DTMF Decoder IC:
The MT8870 is a complete DTMF receiver integrating both the
bandsplit filter and digital decoder functions. The filter section uses
switched capacitor techniques for high and low group filters; the decoder
uses digital counting techniques to detect and decode all 16 DTMF tonepairs into a 4-bit code.
The MT8870 monolithic DTMF receiver offers small size, low power
consumption and high performance. Its architecture consists of a bandsplit
filter section, which separates the high and low group tones, followed by a
digital counting section which verifies the frequency and duration of the
received tones before passing the corresponding code to the output bus.
ATMEGA16 Microcontroller:
ATmega16 is an 8-bit high performance microcontroller of Atmel’s
Mega AVR family with low power consumption. Atmega16 is based on
enhanced RISC (Reduced Instruction Set Computing) architecture with 131
powerful instructions. Most of the instructions execute in one machine
cycle. Atmega16 can work on a maximum frequency of 16MHz.ATmega16
has 16 KB programmable flash memory.
ATmega16 is a 40 pin microcontroller. There are 32 I/O
(input/output) lines which are divided into four 8-bit ports designated as
PORTA, PORTB, PORTC and PORTD.
Each port on a tiny or mega AVR drives up to eight pins and is
controlled by three 8-bit registers: DDRx, PORTx and PINx, where x is the
port identifier.
DDRx: Data Direction Register, configures the pins as either inputs or
outputs.
PORTx: Output port register. Sets the output value on pins configured
as outputs. Enables or disables the pull up resistor on pins configured as
inputs.
PINx: Input register, used to read an input signal. On some devices
(but not all, check the
datasheet), this register can be used for pin
toggling: writing a logic one to a PINx bit toggles the
corresponding bit in
PORTx, irrespective of the setting of the DDRx bit.
L293D Motor driver IC:
L293D is a dual H-bridge motor driver integrated circuit (IC).
Motor drivers act as current amplifiers since they take a low-current control
signal and provide a higher-current signal. This higher current signal is
used to drive the motors.
L293D contains two inbuilt H-bridge driver circuits. In its common
mode of operation, two DC motors can be driven simultaneously, both in
forward and reverse direction. The motor operations of two motors can be
controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will
stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise
and anticlockwise directions, respectively.
Enable pins 1 and 9 (corresponding to the two motors) must be
high for motors to start operating. When an enable input is high, the
associated driver gets enabled. As a result, the outputs become active and
work in phase with their inputs. Similarly, when the enable input is low, that
driver is disabled, and their outputs are off and in the high-impedance state.
Pin No
Function
Name
1
Enable pin for Motor 1; active high
Enable 1,2
2
Input 1 for Motor 1
Input 1
3
Output 1 for Motor 1
Output 1
4
Ground (0V)
Ground
5
Ground (0V)
Ground
6
Output 2 for Motor 1
Output 2
7
Input 2 for Motor 1
Input 2
8
Supply voltage for Motors; 9-12V (up to 36V)
Vcc 2
9
Enable pin for Motor 2; active high
Enable 3,4
10
Input 1 for Motor 1
Input 3
11
Output 1 for Motor 1
Output 3
12
Ground (0V)
Ground
13
Ground (0V)
Ground
14
Output 2 for Motor 1
Output 4
15
Input2 for Motor 1
Input 4
16
Supply voltage; 5V (up to 36V)
Vcc 1
BLOCK DIAGRAM:
CIRCUIT DIAGRAM:
WORKING:
1.
2.
3.
4.
5.
Connect the cell phone to circuit through audio jack.
Call the cell phone from a remote phone.
Press numbers on the keypad in the course of the call.
Now DTMF tones are sent by remote phone to the circuit
The Decoder IC decodes the tone and send equivalent binary
number to the microcontroller.
6. Robot will work according to the program set in the microcontroller.
FUTURE SCOPES:
● IR Sensors:
IR sensors can be used to automatically detect & avoid
obstacles if the robot goes beyond line of sight. This avoids damage to the
vehicle if we are maneuvering it from a distant place.
● Password Protection:
Project can be modified in order to password protect the
robot so that it can be operated only if correct password is entered. Either
cell phone should be password protected or necessary modification should
be made in the assembly language code. This introduces conditioned
access & increases security to a great extent.
● Alarm Phone Dialer:
By replacing DTMF Decoder IC MT8870 by a 'DTMF
Transceiver IC’ MT8880, DTMF tones can be generated from the robot. So,
a project called 'Alarm Phone Dialer' can be built which will generate
necessary alarms for something that is desired to be monitored (usually by
triggering a relay). For example, a high water alarm, low temperature
alarm, opening of back window, garage door, etc. When the system is
activated it will call a number of programmed numbers to let the user know
the alarm has been activated. This would be great to get alerts of alarm
conditions from home when user is at work.
● Adding a Camera: If the current project is interfaced with a camera
(e.g. a Webcam) robot can be driven beyond line-of-sight & range
becomes practically unlimited as GSM networks have a very large
range.
CONCLUSION
Thus the robot was built using DTMF technology.All irregularities were
checked then tested and found to have a satisfactory output. The
construction was carried out with care. The precautions were taken during
the soldering.As stated above this system can be further improvised to
carry out more advanced tasks and operations.