Minor Project Report

CHAPTER- 1 Introduction 1.1) Aim: To design Dual Tone Multi Frequency signal transmitter and receiver which are capable of sending sequence of numbers at regular intervals in DTMF format to switch ON various devices.

1.2) General Description of Entire System: System consists of one master DTMF code transmitter and one master DTMF code receiver. DTMF transmitter includes keypad, DTMF signal generator, and mixer circuit for modulation, amplifier and a transmission antenna. DTMF receiver includes Receiver antenna, mixer circuit for demodulation, DTMF decoder, and Digital logic to switch on the devices. Advantage is that many devices can be interfaced to one DTMF receiver. When the corresponding DTMF code for a particular device is received by the receiver then that device only responds accordingly. Transmission and Reception of DTMF code will be on the frequency range used in RCIED’s (4 MHz – 12 MHz). 1.3) Working Principle of Entire System: DTMF sig.

DTMF Keypad

DTMF signal generator

Antenna (4 – 12) MHZ Mixer Circuit / Modulator

Amplifier

Fig 1.1 Block Diagram of Transmitter DTMF sig. DTMF signal Decoder

LOGIC

Antenna

(4 – 12) MHZ Mixer Circuit / Demodulator

Filters

Fig 1.2 Block Diagram of Receiver

….……… To different Devices

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1.3.1) Transmitter Circuit: When the key is pressed in the keypad, DTMF signal generator produces DTMF signal corresponding to that key. DTMF signal is FM modulated and we set center frequency ranges from 4MHz – 12MHz. This signal is fed to amplifier and transmitted through antenna as shown in fig 1.1.

1.3.2) Receiver Circuit: The working principle of receiver circuit is shown in the fig.1.2. Receiver antenna receives signal, which passes through filters and gets demodulated to give the original DTMF signal. This signal is given to DTMF signal decoder and decoded output is passed through logic, to operate appropriate devices.

1.4) Block Diagram of System Implemented: For the purpose of demonstration, part of the system is implemented. The system implemented has wired transmission of DTMF signal between Transmitter and Receiver as shown in fig 1.3. Controller is used in the transmitter side, instead of keypad for the generation of sequence of numbers at regular intervals. Controller used in the receiver side switches ON devices against the device code received. Displays are interfaced to check the transmitted code.

PIC

TRANSMITTER

DTMF Generator

Transmission Line

DISPLAY

DTMF Receiver

RECEIVER

DEVICES

Fig 1.3 Block Diagram of the system implemented

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PIC

DISPLAY

1.5) Organization of the Report:

Chapter 1: Gives introduction about the complete system and the system implemented

Chapter 2: Details about the designing of DTMF signal transmitter system and logic for the generation of sequence of numbers

Chapter 3: Details about the designing of DTMF signal receiver circuit and logic to switch on the various devices

Chapter 4: Discussion about the results obtained

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Chapter 2 DTMF Transmitter

2.1) Introduction: This Chapter deals with basics of DTMF signal, frequency bands of each key, keypad interfaced circuit to explain the working principle of DTMF signal generator IC MV5089. In order to demonstrate the system, PIC is interfaced with MV5089 to generate the sequence of codes. This chapter also explains the logic implemented in PIC through flow chart. For the convenient of demonstration 7 segment LED is interfaced with the transmitter circuit. Finally, explains the entire transmitter side operation with circuit diagram. 2.2) General Description: DTMF (Dual Tone Multi Frequency) generation is a composite audio signal of two tones between the frequency of 697Hz and 1633Hz. The DTMF keypad is arranged such that each row will have its own unique tone frequency (ranging from 697 Hz – 941 Hz) and each column will have its own unique tone (ranging from 1209 Hz – 1633Hz). Representation of the typical DTMF keypad and their associated row/column frequencies are shown in fig 2.1.

Fig 2.1 Organization of Keypad

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Frequency Band Selection for the Low Tone Group and for the High Tone Group is given in Fig 2.2.

Fig 2.2 LOW tone and HIGH tone Bands

Tone Groups are selected such that both High Tone and Low Tone should not overlap with each other at the same time each frequency band of one tone group should not overlap with each other to avoid the deterioration of valuable signal. In addition, it made easy to design Band pass filters on the receiver side.

2.3) DTMF Signal Generation Using MV5089:

In order to generate DTMF signal, DTMF signal generator IC MV 5089 is used. It has got 4 column pins and 4 row pins. All the 8 pins are internally pulled high and will accept the low level signal. A keypad can be interfaced with MV5089 as shown in the fig 2.3. Whenever a particular key is pressed corresponding row and column pins will be connected to ground. Once the column and rows pins are connected to ground, then the corresponding HIGH tone and LOW tone will be generated. For example, if the number ‘1’ is pressed in the keypad, the tones 1209Hz and 697Hz will be generated. MV5089 will give DTMF signal at TONE output by combining High Tone and Low Tone.

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Fig 2.3 Interface of Keypad with MV5089

2.4) Interfacing PIC with MV5089: Main idea is to Pre- activate the RCIED’s; there many sequences of number should be generated for various IF Bands. In that context, generating sequence of numbers through key pad is impossible; to achieve that PIC 16F870 Controller is interfaced with the DTMF signal generator as shown in fig 2.4.

In this project, to demonstrate the operation of the entire system, three devices are activated by generating the DTMF signal. Each Device will have unique device code which of three digits. (Device 1 = 567, Device 2 = 653 Device3 = 521). Of the three digits of device code, digits are sent one after another. And finally devices will be activated one by one.

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RB4 RB5 RB6 RB7 PIC 16F870 RB0 RB1 RB2 RB3

Fig 2.4 PIC Interfaced with MV5089

Main purpose of Controller is to store all the devices code, separate them into single digit and send them one by one to DTMF signal generator. Finally each digit is sent to receiver in the form of DTMF signal. For example to activate the DEVICE 1, Device Code for that is taken 567 and separated into 5, 6, 7 and stored in separate variables. Send 5 first, followed by 6 and 7.

2.5) Logic Implemented in PIC 16F870

2.5.1) Algorithm:

1) Take one Device code 2) Separate the device code into single digits 3) Store the three single digits in separate variables 4) Send the digits one by one 5) According to the digit, send LOW signals to corresponding Column and Row

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2.5.2) Flow Chart:

START

Take one Device Code

Separate it into three single digits & store it separate variables NO

if Send ==3

Send +1 Send LOW Signal to Corresponding Column and ROW

YES

Device +1 NO

If Device ==3

YES

STOP Flow chart 2.1 Logic for transmitter circuit

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2.6) Display Interfacing: For the convenient of demonstration, a 7 segment display is interfaced with PIC through the driver IC 4511. So, whatever number sent to DTMF signal generator, will also be sent to 7 Segment display. Complete block diagram of Transmitter side is shown in fig 2.5. Tone out

PIC 16F870

DTMF Signal Generator

7 seg. LED Driver

Fig 2.5 Complete Transmitter System Block Diagram

2.7) Working of Transmitter Circuit: Entire transmitter circuit diagram is shown in the fig.2.6. PIC is interfaced to MV5089 through PORTB. PORT C of PIC is interfaced with the 7 segment LED driver. LSBs (RB0-RB4) are used for ROW pins and MSBs (RB4-RB7) are used for COLUMN pins. PORTB always output FFh, that is, HIGH to all pins, so no number will be generated. In order to send a particular number, corresponding column and row pins are made LOW. Once the column and rows pins are made LOW, DTMF generator will send the corresponding DTMF signal to receiver. At the same time, same number is sent to LED driver through PORTC of PIC, to display in 7 segment LED. In this way, sequence of numbers are generated and displayed in 7 segment LED simultaneously.

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Vdd RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0

Col4 Col3 Col2 Col1 MV5089 Row1 Row2 Row3 Row4

RC0 RC1 RC2 RC3

A B C D

a b c d

4511

e f g

TONE O/P R1 390

0

330 ohm 330 ohm 330 ohm 330 ohm 330 ohm 330 ohm 330 ohm

7 Segment LED Fig 2.6 Complete Transmitter System Circuit Diagram

2.8) Conclusion: This chapter explained the working of DTMF signal generator, logic implemented in PIC to send sequence of numbers, interfacing of PIC with DTMF generator and 7 segment LED and finally the description of the entire DTMF transmitter system.

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Chapter 3 DTMF Receiver 3.1) Introduction: This chapter deals with basic concept of DTMF signal decoding, introduce the IC CM8870 used for the decoding, design of receiver circuit to detect valid DTMF signal, the way how PIC is interfaced between decoder and the devices to be switched ON, the logic implemented in PIC through flow chart and finally working of entire receiver circuit. 3.2) General Description: On the receiver side, first Low tone and High tone is separated using band-spilt filter into two discrete signals as shown in fig 3.1.

High Group Filters

Digital Filters

Low Group Filters

Digital Filters

I/P DTMF Signal

Fig 3.1. Separation High & Low tone

Then the separated signals are given to the corresponding decoding logic and depending upon the HIGH tone and LOW tone received digital output will be produced as shown in fig 3.2.

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Fig 3.2 Interface of Keypad with MV5089

3.3)

DTMF Signal Receiver Using CM8870:

In order to decode the DTMF signal, DTMF signal receiver CM8870 is used. Block diagram is shown in fig 3.3 It is having Input operational amplifier with an option for gain select. This is used in inverting configuration with unity gain. Min voltage of DTMF signal that can be detected should be not less than 1.5V. If there is any Transmission loss in the signal, then gain of receiver can be selected accordingly.

Q1, Q2, Q3, Q4 are the decoded output. The signal StD (delayed steering) gives high signal when the decoded out put is latched

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Fig 3.3 Block diagram of CM8870

3.4) DTMF Signal Receiver Design:

Receiver should be designed properly to detect the valid DTMF signal. Timing Diagram is given fig 3.4 for CM8870 IC. ESt -> Early Steering Output. Indicates detection of valid tone Frequencies.

St/GT -> Steering INPUT/GUARD TIME OUTPUT. Drives External RC Timing Circuit StD -> Delayed steering output. Presents logic high when a received tone pair has been registered and the output latch is updated. Returns to logic low when the voltage on St/GT falls below VTSt.

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Fig 3.4. Timing diagram of CM8870

T REC = Minimum time required to detect the valid DTMF signal Typical value is 40ms

T REC = tDP + tGTP: tDP = Minimum Time required by the IC to detect the Signal tDP = 14 ms tGTP = Minimum time required to start conversion after tDP tGTP = this can be designed by RC circuit such that sum of tGTP & tDP should be greater than 40ms

here tGTP is designed for 30ms R = 300K C = .1µF Input op-amp is designed for unity gain by two 100K ohm resistors. Designed circuit is shown in fig 3.5 and component values are given below the figure

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Fig 3.5. Designed Receiver Circuit

C2 = .1µF R3 = 300 K ohm R1 = 100K ohm R2 = 100K ohm

3.5) Interfacing PIC with Receiver IC:

From the Transmitter, it is going to get three digit codes for three devices. The purpose of the PIC is to get the sequences of single digit of codes, combine the single digit code to three digit code of the device. The unique three digit code for the devices, also stored in the receiver side. If the receiver PIC gets the same three digit code it will switch ON the device corresponding to that code. The signal StD of CM8870 is connected to the interrupt pin of the PIC 870

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3.5.1) Algorithm:

1) On Interrupt, get the decoded code 2) On receiving three codes, combine it to form single three digit code 3) The final three digit code is compared with the pre defined Device Code stored in PIC 4) If the Code matches switch ON the corresponding device. 3.5.2) Flow Chart

Wait on Interrupt

Get the decoded Code from receiver

NO

If Receive= =3

YES Combine three single digits to one three digit code

YES If Received Code == Dev. Code

NO

SWITCH ON the DEVICE

NO If Device==3

STOP YES

Flow chart 3.1.Logic to switch on the Devices

Display: 7-Segment Display is also interfaced in the receiver side to check the received code

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3.6)

Working of Receiver Circuit: Complete Receiver circuit diagram is show in the fig 3.6. PORTB of PIC (RB4 -

RB7) is interfaced with CM 8870 to get the decoded output. StD pin of CM8870 is connected to interrupt to indicate the end of decoding. PORT C is used to switch ON the devices. PORT A is used to interface the display. When the DTMF receiver receives the DTMF signal for valid duration, it decodes and gives output at Q1, Q2, Q3, Q4 and interrupt is given to PIC. Once the PIC is interrupted, it will get the code on MSBs of PORTB and sends the same number to LED display. As soon as PIC gets the entire code it will switch on the corresponding device through PORTC.

PIC 16F870 PORT C Interrupt (RB0) RB4 – RB7

330 ohm 330 ohm 330 ohm

a b c d

330 ohm

e

330 ohm

f g

330 ohm 330 ohm

ABCD

PORTA(RA0-RA3)

4511

330 ohm

Fig 3.6. Complete Receiver System Circuit Diagram

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D E V I C E S

3.7)

Conclusion:

This chapter dealt with basic DTMF decoding principle, interfacing of PIC with DTMF signal decoder and devices, explained logic implemented in PIC to switch ON the devices on receiving correct device code and finally description of the entire DTMF receiver system.

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Chapter 4:

Results and Discussion

4.1) Transmitter:

1) DTMF signals are generated by interfacing PIC with MV5089 DTMF signal for the number 5 and 1 are shown in fig 4.1 and fig 4.2

Fig 4.1 DTMF Signal for Number 5

Fig 4.2 DTMF Signal for Number 1

2) Output of 7 – segment LED is also cross checked with the DTMF signal using CRO

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3) Device Code for Device 1 = 567 Device Code for Device 2 = 653 Device Code for Device 3 = 521 PIC controller on the transmitter side is programmed in such a way that it will send device code of Device 1 first, followed by Device 2 and Device 3. These codes are verified by the display interfaced with the transmitter. After sending the complete set of codes, transmitter will stop sending signals but for the purpose of demonstration, transmitter will again start to send the signal from the beginning.

4.2) Receiver:

1) On the receiver side, received DTMF signal is decoded and corresponding digital code is sent to PIC and decoded code is displayed in 7 – segment LED. This display is cross checked with transmitter display. 2) PIC Interfaced to get digital code of receiver circuit on interrupt. PIC will accumulate the codes until it receives three numbers. Once if it receives three numbers, it will form a device code and check received device code with the pre defined device code. If it matches with any one of the device code, PIC will switch ON the device corresponding to that code through PORT C. This is demonstrated by keeping LEDs in the place of devices.

4.3) Work To Be Done: In this project, DTMF signal generation and DTMF signal decoding is completed. Here, DTMF signal transmission and reception is done through wire. In next semester, DTMF signal transmission and reception will be made wireless and transmitted by having the center frequencies ranges from 4MHz to 12MHz. Experimental analysis will be done at different distances for different input power. Final system will be capable of switching on the remotely located devices

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APPENDIX A PIC Codes for Transmitter and Receiver

TRANSMITTER side Code:

#include #define delay1U asm("nop"); int devicet1,devicet2,devicet3,i1,i2,i3; char i=0,led, dnum,send,stop;

void displayportb (int disp){

switch (disp) {

case 1: PORTB = 0XEE; PORTC = 0x11; break; case 2: PORTB = 0XDE; PORTC = 0x22; break; case 3: PORTB = 0XBE; PORTC = 0x33;

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break; case 4: PORTB = 0XED; PORTC = 0x44; break; case 5: PORTB = 0XDD; PORTC = 0x55; break;

case 6: PORTB = 0XBD; PORTC = 0x66; break; case 7: PORTB = 0XEB; PORTC = 0x77; break; case 8: PORTB = 0XDB; PORTC = 0x88; break; case 9: PORTB = 0XBB; PORTC = 0x99; break; }

} void displayled(int disp_led) { switch(disp_led){

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case 1: PORTA = 0X0E; break; case 2: PORTA = 0X0D ; break; case 3: PORTA = 0X0B; break; } } void seperate(int device) {

i1 = i2 = device/10; i1 = i1 *10; i1 = device - i1; i3 = device/100; i2 = i2 - (i3*10); i2=i2; }

void sending() {

//PORTA = 0X3F; if(send == 1){ displayportb(i1); send++; } else if (send == 2) { displayportb(i2); send++;

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} else { displayportb(i3); send =1; dnum++; } if(led==4){ led = 1; }

displayled(led); led++; }

void interrupt isr() { if(T0IF==1) { if(i==0) { i=16; if(stop==0){ if(dnum == 4) { dnum =1; } if(dnum == 1){ seperate(devicet1); sending();

}

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else if(dnum == 2) { seperate(devicet2); sending();

} else if(dnum == 3) { seperate(devicet3); sending(); } stop =1; } else{ stop = 0; PORTB = 0XFF; PORTA = 0X3F; }

} else { i--; } INTCON =0XE0; T0IF=0; } }

void main() {

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OPTION=0X87; ADCON1 = 0X06; dnum =1; led = 1; devicet1 = 965; devicet2 = 356; devicet3 = 125; send = 1; i1=0; i2=0; i3=0; TRISA=0X00; TRISB=0X00; TRISC=0X00; PORTA=0X0F; PORTB=0XFF; PORTC=0X00;

INTCON=0XE0;

TMR0=0x00; while(1) { INTCON= 0XE0; } }

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RECEIVER side Code:

#include char recnum,receive; int ir1,ir2,ir3,devcode; void checkdevice(int device) { switch(device){ case 0X569: PORTC = 0X11; break; case 0X653: PORTC = 0X33 ; break; case 0X521: PORTC = 0X77; break; } } void display7seg (char disp){

switch (disp) {

case 0x10: PORTA = 0X01; break; case 0X20: PORTA = 0X02;

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break; case 0X30: PORTA = 0X03; break; case 0X40: PORTA = 0X04; break; case 0X50: PORTA = 0X05; break; case 0X60: PORTA = 0X06; break; case 0X70: PORTA = 0X07; break; case 0X80: PORTA = 0X08; break; case 0X90: PORTA = 0X09; break; } } void interrupt isr() { if(INTF==1) { recnum = PORTB & 0XF0; display7seg(recnum);

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if(receive==1){ ir1 = recnum ; ir1 = ir1*0X10;

} else if(receive==2) { ir2 = recnum; } else if(receive==3) { receive = 0; ir3 = recnum/0X10; devcode = ir1+ir2+ir3; checkdevice(devcode); } INTF =0; receive++; } } void main() { OPTION=0XC0; ADCON1 = 0X06; receive=1; TRISA = 0X00; TRISB = 0XFF; TRISC = 0X00; PORTA = 0XFF; INTCON=0XD0; while(1)

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{ } }

APPENDIX B

PIC 16F870:

Pin diagram:

Registers Used in Program

1) ADCON1

30

2) INTCON

31

3) OPTION

32

APPENDIX C

DTMF Signal Generator: MV 5089:

Pin Details:

Block Diagram:

33

ROW and COLUMN Inputs

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APPENDIX – D

DTMF Signal Receiver CM8870:

PIN details:

Functional Block Diagram

35

36

Timing Diagram:

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Explanation of Symbols Vin ESt St/GT Q1-Q4 4StD TOE tREC tREC tID tDO tDP tDA tGTP tGTA

DTMF COMPOSITE INPUT SIGNAL. EARLY STEERING OUTPUT. INDICATES DETECTION OF VALID TONE FREQUENCIES. STEERING INPUT/GUARD TIME OUTPUT. DRIVES EXTERNAL RC TIMING CIRCUIT. BIT DECODED TONE OUTPUT. DELAYED STEERING OUTPUT. INDICATES THAT VALID FREQUENCIES HAVE BEEN PRESENT/ABSENT FOR THE REQUIRED GUARD TIME THUS CONSTITUTING A VALID SIGNAL. TONE OUTPUT ENABLE (INPUT). A LOW LEVEL SHIFTS Q1-Q4 TO ITS HIGH IMPEDANCE STATE. MAXIMUM DTMF SIGNAL DURATION NOT DETECED AS VALID MINIMUM DTMF SIGNAL DURATION REQUIRED FOR VALID RECOGNITION MAXIMUM TIME BETWEEN VALID DTMF SIGNALS. MAXIMUM ALLOWABLE DROP OUT DURING VALID DTMF SIGNAL. TIME TO DETECT THE PRESENCE OF VALID DTMF SIGNALS. TIME TO DETECT THE ABSENCE OF VALID DTMF SIGNALS. GUARD TIME, TONE PRESENT. GUARD TIME, TONE ABSENT.

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APPENDIX –E 7 Segment LED Driver: HEF 4511 B Pin Diagram:

Functional Diagram:

Functional Table:

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