DTMF 2

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International Journal of Electronic Engineering Research

ISSN 0975 - 6450 Volume 2 Number 3 (2010) pp. 349–355

© Research India Publications

http://www.ripublication.com/ijeer.htm

Mobile Controlled Robot using DTMF Technology

for Industrial Application

1D. Manojkumar,

2P. Mathankumar,

3E. Saranya and

4S. Pavithradevi

1Project guide- Lecturer/ECE,

2,3,4,5Final ECE,

Velalar College of Engineering & Technology, Erode, IndiaE-mail: [email protected]

Abstract

In this project, we present controlling of a Robot using DTMF technique.

The robot is controlled by a mobile phone that makes call to the other

mobile phone attached to the robot. In the course of the call, if any button

is pressed, tone corresponding to the button pressed is heard at the other

end of the call. This tone is called dual tone multi frequency tone (DTMF).

Using DTMF code, direction of motion of the robot can be controlled bymobile phone. Robot has a RF camera that transmits an actual video at the

operator’s monitor. Based on the received video, the corresponding

comments can be passed from the mobile phone which is connected with

the transmitter side. The comments will be converted to voice using the text

to speech converter at the receiver side. The voice will be heard via the

loud speaker attached to the robot. Gas sensor and smoke sensor are also

interfaced with the robot. In case of any smoke or gas, the sensor senses the

gas or smoke and passes the signal to the alarm. The alarm sound is heard

via a loud speaker.

Keywords: Mobile phones, DTMF decoder, controller, RF camera, TVmonitor.

IntroductionBeing able to achieve reliable communication is an important open area of research to

robotics as well as other technology areas. As interest in robotics continues to grow,

robots are increasingly being integrated in everyday life. The results of this

integration are end-users possessing less and less technical knowledge of the

technology. Currently, the primary mode for robot communication uses RF (radio

frequency). RF is an obvious choice for communication since it allows more

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350 D. Manojkumar et al

information to be transferred at smaller distance. The overall goal of the project is to

control robot over a long distance using DTMF technology efficiently.

DescriptionThe transmitter side is placed in the area which is to be supervised. The receiver

section is placed in the operator side which receives the video from the corresponding

area.

Figure 1: Block diagram of mobile controlled robot.

PIC16F877A

PIC16F877A consists of high performance RISC CPU in which there are only 35

single word instructions to learn. All are single cycle instructions except for program

branches, which are two cycles. Up to 8K x 14 words of FLASH Program Memory,

368 x 8 bytes of data Memory (RAM) and 256 x 8 bytes of EEPROM Data Memory

are available.PIC16F877A is a 40 pin microcontroller

The peripheral features includes a Timer0 which is an 8-bit timer/counter with an8-bit prescaler, a Timer1 which is a 16-bit timer/counter with prescaler which can be

incremented during SLEEP via external crystal/clock, a Timer2 which is an 8-bit

timer/counter with 8-bit period register, prescaler and postscaler, two capture,

compare, PWM modules. The capture is 16-bit and its maximum resolution is

12.5ns.Compare is 16-bit and its maximum resolution is 200ns.PWM‘s maximum

resolution is 10-bit.There is a Synchronous Serial Port (SSP) with SPI (Master mode)

and I2C (Master/Slave).Further PIC16F877A consists of an Universal Synchronous

Asynchronous Receiver Transmitter (USART/SCI) with 9-bit address detection.

Parallel Slave Port (PSP) is 8-bits wide, with external RD, WR and CS controls

(40/44-pin only).

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Mobile Controlled Robot using DTMF Technology 351

The analog features of PIC16F877A includes a 10-bit, up to 8 channel Analog-to-

Digital Converter (A/D), a Brown-out Reset (BOR) and an analog comparator module

with two analog comparators, programmable on-chip voltage reference (VREF)

module, programmable input multiplexing from device inputs and internal voltage

reference. Comparator outputs are externally accessible.

DTMF Tone

The DTMF technique outputs distinct representation of 16 common alphanumeric

characters (0-9, A-D, *, #) on the telephone. The lowest frequency used is 697Hz and

the highest frequency used is 1633Hz, as shown in Table 1.

Table 1: DTMF Keypad.

The DTMF keypad is arranged such that each row will have its own unique tonefrequency and also each column will have its own unique tone frequency. Above is a

representation of the typical DTMF keypad and the associated row/column

frequencies. By pressing a key, for example 5, will generate a dual tone consisting of

770 Hz for the low group and 1336 Hz for the high group.

DTMF Decoder

The MT-8870 is a DTMF Receiver that integrates both band split filter and decoder

functions into a single 18-pin DIP or SOIC package. It is manufactured using CMOS

process technology. The MT-8870 offers low power consumption (35 mW max) and

precise data handling.

Figure 2: Pin configuration of MT-8870.

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Its filter section uses switched capacitor technology for both the high and low

group filters and for dial tone rejection. Its decoder uses digital counting techniques

to detect and decode all 16 DTMF tone pairs into a 4-bit code. External component

count is minimized by provision of an on-chip differential input amplifier, clock

generator, and latched tri-state interface bus. Minimal external components required

includes a low-cost 3.579545 MHz color burst crystal, a timing resistor, and a timing

capacitor.

The filter section is used for separation of the low-group and high group tones and

it is achieved by applying the DTMF signal to the inputs of two sixth order switched

capacitor band pass filters, the bandwidths of which corresponds to the low and high

group frequencies. The filter section also incorporates notches at 350 and 440 Hz for

exceptional dial tone rejection. Each filter output is followed by a single order

switched capacitor filter section which smoothes the signals prior to limiting. Limitingis performed by high-gain comparators which are provided with hysteresis to prevent

detection of unwanted low-level signals. The outputs of the comparators provide full

rail logic swings at the frequencies of the incoming DTMF signals.

Following the filter section is a decoder employing digital counting techniques to

determine the frequencies of the incoming tones and to verify that they correspond to

the standard DTMF frequencies.

Text To Speech Converter

The integrated text-to-speech processor consists of high voice quality and unlimited

vocabulary. It converts any ASCII text into speech automatically, it is capable of very

high reading rates, it can add/modify messages by simply editing a text file and it hason-the-fly control of speed, pitch, volume, etc. The converted voice from the text to

speech converter is heard via the loudspeaker. The loudspeaker is interfaced with the

robot.

The text to speech converter is mainly used in Robotics, ATM machines, Vending

and ticketing machines, remote diagnostic reporting, Dial-up information systems,

Electronic test and measurement, Security systems.

Figure 3: Pin configuration of L293D.

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Table 2: Robot movement.

Left Motor Right Motor Robot Movement

Straight Straight Straight

Stop Straight Left

Reverse Straight Sharp Left

Straight Stop Right

Straight Reverse Sharp Right

Reverse Reverse Reverse

RF Camera

RF camera consists of a 2.4GHz Audio/Video wireless RF Transmitter.The most popular 2.4GHz ISM band is used and it is designed with high reliability.

Airwave RF module is compliance with the criteria of FCC and R&TTE which can

transmit a wide band audio & video signals up to 100 meters in an open area. RF

camera is of compact size and it consumes a low power. RF camera is composed of a

highly efficient FM-FM modulation/demodulation scheme. No external audio circuit

is needed. The number of Channels selected is four and default value is ch4 (not

enable). Other channels can be selected by applying low to enable.

RF Transmitter

RF transmitter transmits video and sound to the RF receiver which is connected to the

TV located anywhere (up to 100 ft. away).The RF transmitter consists of a wireless2.4 GHz technology which is combined with a wireless power source that produces a

video without any delay.

RF Receiver

The RF Video Receiver works with Wireless Cameras. The Camera converts video

into wireless radio frequency (RF) signals and transmits them to the Video Receiver

which is connected to a TV anywhere (up to 100 ft. away from the Camera). The

Video Receiver converts the signals back to video signals, which are fed through a

cable to our TV's Video input jack.

Sensors

The gas and smoke sensors are interfaced with the robot. A gas detector is a device

which detects the presence of various gases within an area. It acts as a part of the

system to warn about gases that might be harmful to humans and animals. Gas

detectors can be used to detect combustible, toxic oxygen and CO2 gases. This device

may be used in firefighting. Laboratories, MRI rooms, pharmaceutical,

semiconductor, and cryogenic suppliers commonly use the gas detectors.

Smoke detectors are typically housed in a disk-shaped plastic enclosure about

150 millimeters (6 in) in diameter and 25 millimeters (1 in) thick. The radiation

produced by fire passes through an ionization chamber, an air-filled space between

two electrodes, and permits a small, constant current between the electrodes. Any

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Mobile Controlled Robot using DTMF Technology 355

smoke that enters the chamber absorbs the alpha particles, which reduces the

ionization and interrupts this current, setting off the alarm.

Conclusion & Future ScopeSo far the present system is designed mainly for the supervision applications. In the

area of suspectance, the robot can be directed and if any smoke or gas is identified the

robot can produce alarm and also informs the operator. The comments from the

operator can also be transmitted to the area where the robot moves. Further the key

board can be interfaced with the TV connected at receiver side to increase the number

of comments given to the robot. Amplifier is needed to be connected to the speaker of

the mobile interfaced with the robot to pass the comments directly through mobile

from the remote mobile. The RF camera can be replaced with the 3G mobile for longdistance communication. The above system can also used for military purpose as

bomb detection and as spy robot.

References

[1] www.datasheetarchive.com/MT8870-datasheet.html

[2] www.microchip.com

[3] ”Feasibility Study of DTMF Communications for Robots”, UWEE Technical

Report, Number UWEETR-2004-0013, April 6, 2004.

[4] www.nex-robotics.com/.../motor-controllers/l293d-motor-driver-ic.html[5] www.ccsrobotics.com

[6] www.active-robots.com/.../av-modules.shtml - United Kingdom

[7] www.spyville.com/camera-detector.html

[8] “Robots, Androids, and Animations 12 Incredible Projects You Can Build” by

John Iovine Second Edition McGraw-Hill.

[9] “PDA Robotics Using Your Personal Digital Assistant to Control Your Robot”

by Douglas H. Williams McGraw-Hill.

[10] “Remote robot control system based on DTMF of mobile phone” published

in 6th IEEE International Conference.

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