GOVERNMENT COLLEGE OF ENGINEERING, CHANDRAPUR

DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING

2013-14

“ DTMF (Dual Tone Multi Frequency) Based

Load Control.”

CONTENTS

• Why DTMF based different load control?• Operation• Circuit Diagram• Component List• Microcontroller• DTMF Decoder• Advantages• Applications• Conclusion• Reference

WHY DTMF BASED DIFFERENT LOAD

CONTROL?

In industries, the loads are spread over alarge area and thus, operating these loads is a verytiresome and difficult task. In agricultural fieldsalso, pumps and other loads are connected over alarge area and hence it is difficult for the farmer tooperate all the loads and similarly for house holdloads. Keeping these problems in mind, theproposed system has been designed which usesDTMF technology to control the loads remotely.

A cell phone is interfaced to a DTMF decoder in thesystem from its audio output socket for receiving tonecommands. The receiving cell phone codes are convertedinto digital commands by using a DTMF Decoder which willidentify the frequency of the key and convert that frequencyto its equivalent digital code which is then fed to amicrocontroller (8051 family). As per the commands sentfrom the sender’s mobile, the microcontroller will sendsignals through a buffer to actuate the respective loads byturning the relays ON/OFF. These relays are actuated by arelay driver IC interfaced to the microcontroller.

OPERATION

CIRCUIT DIAGRAM

Fig. 1.2 Circuit Diagram of DTMF System

COMPONENTS NEEDED

Sr.No. EQUIPMENTS

1 IC 8051 MC

2 MT 8870 DTMF IC

3 CRYSTAL (3.579545MHZ)

4 VOLTAGE REGULATOR

5 2 LINE LCD DISPLAY

6 CRYSTAL OSCILLATOR(11.0592MHZ)

7 DIODE

8 PUSH BUTTON

9 LEDS

10 RESISTER(220Ω,4.7KΩ,10KΩ) BOX

11 CAPACITORS(10UF,1000UF)

12 MOTOR

13 L293D

14 MISCELLANEOUS

MICROCONTROLLER

The following are some of the capabilities of 8051 microcontroller:-

1. Internal ROM and RAM 2. I/O ports with programmable pins 3. Timers and counters 4. Serial data communication

DTMF DECODER

•DTMF keypads are employed in almost all landline

and mobile handsets. Thus this technology is used

in the telephone switching centers to identify the

number dialed by the caller.

•The decoder distinguishes the DTMF tones and

produces the binary sequence equivalent to key

pressed in a DTMF (Dual Tone Multi Frequency)

keypad.

•The circuit uses M-8870 DTMF decoder IC which

decodes tone generated by the keypad of cell

phone.

•DTMF signals can be tapped directly from the

microphone pin of cell phone device. Cut the

microphone wire and you will get two wires red and

green. The red wire is the DTMF input to the circuit.

•The signals from the microphone wire are

processed by the DTMF decoder IC which generates

an equivalent binary sequence as a parallel output

like Q1, Q2, Q3, and Q4.

ADVANTAGES

No need to go on field.

Higher Reliability.

Cost Effective.

Many devices can be controlled through single command.

APPLICATIONS

Industrial Automation.

Security Purpose.

For long distance contorlling.

CONCLUSION

We have discussed the purpose, use andimplementation of mobile communication system to controlspeed of DC motor from remote area using mobile. Toachieve this, we have used the concept of relay operationusing decoding of DUAL TONE MULTI FREQUENCY SIGNALING(DTMF) produced by mobile.

We will design a hardware module connected with aprototype load as DC motor and have perform precisecontrol and speed tests as well as braking. Its efficiency isrelatively high as compared to the other similar methods.

All datasheets from www.datasheetcatalog.com

www.Thomson.com/learning

About AT89s8252 from www.atmel.com

www.triindia.co.in

THE 8051 MICROCONTROLLER & EMBEDDED SYSTEMS USING ASSEMBLY

& C- PROGRAMING by Kenneth J. Ayala, Cangage Learning publication.

The Microcontroller Idea Book by Jan Axelson, Penram International

Publishing (INDIA) Pvt. Ltd.

Electronics Project HAND BOOK by Amrit Bir Tiwina, BPB Publication.

Microcontroller Architecture , Programing ,Interfacing & System Design.

By Raj Kamal , PEARSON Publication.

Millman’s Electronics & Device & Circuits . by Jacob Millman , Tata

Mcgraw-Hill Publishing Company Ltd. Pvt.

REFERENCES