1. FORTNIGHT REPORT 1
We have studied the hardware aspect n the different blocks involved in it.
The basic blocks of this part of the system consist of:
1. Ring Detector
2. Relay Activation Circuit
3. A DTMF Decoder
4. A Relay Control For DTMF Decoder
5. Microcontroller
Ring Detector:
The ring detector first detects the incoming signal. A bridge rectifier is connected to the
telephone line. This turns the ringing signal (an alternating voltage) into a pulsating
direct voltage that is smoothened by the condenser and limited with the aid of zener
diodes. The direct voltage across the zener diode is applied to the opto-coupler that
forms as the electrical isolation between the two stages.
DTMF decoder:
The DTMF decoder 8870 performs the function of decoding the digits dialed by the user
in their corresponding binary states and thus making them available for processing in the
microcontroller.
Relay circuits:
We are using two relays that will be performing various tasks as follows:
Relay to control DTMF decoder:
This relay is used to activate and deactivate the 8870 DTMF decoder at variousstrategic
points. It activates the DTMF decoder just before the user is about to dial the digit. It
deactivates the 8870 DTMF decoder immediately after the user has dialed the digit.
Relay to control feedback audio:
This relay is used to connect and disconnect the audio feedback line (explained later)
with the main telephone line after the response from the user is been received.
2. Relay activation circuit:
This forms the heart of the relay circuits as it controls the functioning of relay
according to the inputs it receives from the microcontroller.
Microcontroller to telephone (via Voice chip)
The basic blocks of this part are
1. Microcontroller
2. Voice chip
Microcontroller: this is brain of this part. In this part triggers the appropriate channels i.e
the message in the voice chip based on the instant the receiver is lifted and based on the
response of the user.
Voice chip: this forms the heart of this module (definitely of the circuit as well). The
voice chip along with its external circuitry has the provision to work in the two message,
four message or the eight message mode. This circuitry has a microphone which enables
the storing of any message by directly introducing the speech signal. The proper method
of storing the signal can be obtained from the data sheet of the voice chip included later.
The audio output can be directly taken from the bridge and is given to the telephone wire
itself. Since the obtained audio signal is a very low amplitude signal, it does not interfere
with the normal working of the telephone line.
MICROCONTROLLER TO TELEPHONE (VIA COMPUTER)
The basic blocks of this part of the system consist of:
1. Signal Converter
2. Computer
3. Isolation Transformer
4. Microcontroller
Signal converter:
The function of this block is to convert the output of the microcontroller into the
signal that is compatible enough to be input of the computer. This is done by using
max 232 chip and RS 232 cables. The signal at the output of the microcontroller is of
the range of 0v to 5v. It is converted into a signal in the range of –12v to +12v to be
input to the PC.
3. Computer:
The computer performs the function of sending the proper wave file according to the
input it receives from the microcontroller. There are various respective wave files
stored in its memory which are according to the output depending on the user request.
Isolation transformer:
This is the very important block as it isolates the computer with the high voltage
telephone line (having a potential difference of –60v). The isolation transformer used
is 1:1 600 ohms. The primary is connected to the output of the computer and the
secondary is connected to the feedback telephone line and controlled by relay circuits
(mentioned earlier).
Microcontroller:
This forms the heart of our entire INTERACTIVE VOICE RESPONSE SYSYTEM.
It is a common block to both the parts. It accepts a suitable signal from ring detector
circuit and triggers the relay activation circuit.
It also accepts the output of 8870 DTMF decoder and processes it and gives the
suitable signal to the computer. It controls the working of various functional blocks
and co-ordinates the operation.
4. FORTNIGHT REPORT 2
Here we have studied different flowcharts describing the working of our project.
Ring Signal
detected?
Start
Ring
Continue?
Wait for 10 seconds
Deactivate DTMF
decoder by relay ckt.
Wait for user response
Establish a
dedicated line
Activate Relay to ans.
Pass the audio via the
isolation transformer.
Call terminate
Continue?
Yes
No
No
No
Yes
Yes
Stop
5. Algorithm ( System End )
Step 1 : Dial the number for the Interactive Voice Response System.
Step 2 : Check for the received signal.
Step 3 : If Busy Tone then go to step 4 else go to step 5.
Step 4 : Terminate the call check for redial. If yes go to step 4 if no go to step
10.
Step 5 : Wait for call to be answered.
Step 6 : On being answered dial for the language in which to be answered.
Step 7 : Choose the service for the required information.
Step 8 : Check if you want to continue. If yes go to step 7, if no go to step 9.
Step 9 : Terminate the call.
Step 10 : Stop the system.
6. Flow Chart ( User End )
YES
YES NO
Start
Dial the Number.
Check the
signal
Dial for
Language.
Wait to be
answered.
Ringing
Signal
Call
Terminate
Busy Tone
Stop
Redial?
Choose for
the service.
Continue?
Call
Terminate
Stop
NO
7. Algorithm ( User End )
Step 1 : Check if the ringing signal is present in the telephone line.
Step 2 : If ringing signal is present then wait for 10 seconds, & go to step 3 or else go to
step 1.
Step 3 : If ring continues then activate the relay or else go to step 1.
Step 4 : Establish a dedicated line connection.
Step 5 : Wait for the response of the caller.
Step 6 : Deactivate the DTMF decoder by relay control circuit to save the decoder from
getting false input.
Step 7 : Pass the audio signal via the isolation transformer.
Step 8 : Check if the signal is continued. If yes go to step 3 else go to step 7.
Step 9 : Terminate the call.
Step 10 : Stop the system.
8. FORTNIGHT REPORT 3
Here we have studied the IC description of microcontroller – 89S52 and DTMF
decoder 8870
Microcontroller - 89S52
Pin Diagram of 89S52
10. Usage in our Circuit
The 89s52 is a microcontroller which has in system programming (ISP) which we
found very useful during the testing stage of our circuit.
Since in ISP the memory of the microcontroller is not formatted once the program
is tested, hence we need not re-program the chip again and again.
The primary job of the microcontroller is to trigger the voice channel based on the
appropriate input received.
The input to the microcontroller is at P1.0, P1.1, P1.2, P1.3 which comes from pin
no. 11,12,13,14 of 8870 respectively.
On receiving the input the microcontroller processes it and triggers the voice
channel of the secondary PCB giving an active low signal at pin no P.20, P2.1,
p2.2 ,P.2.3 according to the input.
Another additional function of the microcontroller is to start a delay of 10s which
will be taking care of the instant of false triggering due to error in the line.
11. Features & Application
• Compatible with MCS®-51 Products
• 8K Bytes of In-System Programmable (ISP) Flash Memory
– Endurance: 1000 Write/Erase Cycles
• 4.0V to 5.5V Operating Range
• Fully Static Operation: 0 Hz to 33 MHz
• Three-level Program Memory Lock
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Full Duplex UART Serial Channel
• Low-power Idle and Power-down Modes
• Interrupt Recovery from Power-down Mode
• Watchdog Timer
• Dual Data Pointer
• Power-off Flag
• Fast Programming Time
• Flexible ISP Programming (Byte and Page Mode)
• Green (Pb/Halide-free) Packaging Option
13. Internal Block Diagram of 8870
Usage in our circuit:
The DTMF decoder is basically used to understand what the user wishes to receive. The
input to the DTMF decoder is a tone which has a specialized frequency which intern
depends upon the number punched in by the user on the telephone keypad. Thus at the
input of the DTMF decoder is a tone with a particular voltage level. The basic job of the
DETMF decoder is to convert the input it has received into binary format. In our circuit
the tone is decoded into the binary format and made available to the microcontroller on
pin number 11,12,13,14 with 11 being the LSB and 14 being the MSB.
14. FORTNIGHT REPORT 4
Here we have studied various software aspect with the flowchart and the program
based on it.
Basic Block Diagram of S/W
Start
Initialization
Wait for user response
Call delay of 10 sec
Message played accordingly
Relay 2 & 1 disconnected
Stop
Yes
No
No
Yes
P2.5 high ?
P2.5 high ?
Count the no. of high & low pulses
Relay 1 & 2 is connected and
welcoming message is played
15. Description of S/W Block
The first step in our program is the initialization of RAM loations, vector
addresses and interrupts initialization.
The second step in our program is the start of the main program in which
initially P2.5 is monitored by the microcontroller.
Once the P2.5 goes high the program counts the total number of active high
and active low signal at this pin.
Next in the program a delay of 10s is started.
At the end of the 10s delay if P2.5 is still high relay1 and relay2 are connected
and the welcoming message is played.
Otherwise the program is terminated and the program once again monitors
P2.5 until it goes high.
After first message is played the system waits for user response to play the
remaining messages accordingly.
At the end of program relay1 and relay2 are disconnected and the program
stops.
16. Software Code
org 0000h
Begin: ajmp start
org 0003h
ajmp Terminate
reti
org 000bh
reti
org 0013h
reti
org 001bh
reti
org 0023h
reti
start: mov a,#00h ;Disable interrupt
mov ie,a
clr a ;Clear the contents of Internal RAM
mov r0,#7fh
clrit: mov @r0,a
djnz r0,clrit
mov sp,#30h ;Initialize Stack Pointer
mov psw,#00h ;Select Bank Zero
clr P1.4
clr P3.5
call delay1
mov P2,#0ffh
mov r7,#05h
Here: jb P2.5,Space ;Ring detection
sjmp Here
Space: jnb P2.5,Space2
sjmp space
Space2: djnz r7,Here
call delay10
19. loop2: mov r3,#40h
loop1: djnz r3,loop1
djnz r2,loop2
djnz r1,loop3
djnz r0,loop4
ret
delay5: mov r0,#05h
loop41: mov r1,#50h
loop31: mov r2,#80h
loop21: mov r3,#40h
loop11: djnz r3,loop11
djnz r2,loop21
djnz r1,loop31
djnz r0,loop41
ret
delay1: mov r0,#02h
loop411: mov r1,#50h
loop311: mov r2,#80h
loop211: mov r3,#40h
loop111: djnz r3,loop111
djnz r2,loop211
djnz r1,loop311
djnz r0,loop411
ret
Once the PCB was ready and the component mounting was done we started testing
smaller test programs in order to reach the final program. We faced the following
problems and found the solutions after logically pondering over it.
1. While using 89C51 the program was erased from the RAM after every single test.
Hence we switched over to 89S52 which has ISP
capabilities
2. The grounding of various nodes in the PCB was not proper. We took the help of
multimeter to identify those nodes and ground them accordingly.
3. The ring detector circuit was not working properly. After extensive research on
the internet we found the ring detector circuit that employed 6N139 as the
optocoupler.
20. 4. Audio not reaching the telephone handset. The problem lied in the mismatching
of the resistance of primary and secondary that was supposed to be 600ohms.
5. Relay not getting 12V. This was the mistake of the PCB manufacturer who did
not provide a connection. Hence we had to use a jumper.
6. Audio not properly audible. The solution lied in the proper tunning of the
potentiometer which dealt with the sampling rate and the volume control.
7. Automatic triggering of the voice chip. The ground pin of the port2 was
connected hence it received active low trigger ring throughout the duration for
which the system was on.
8. The DTMF was not working properly i.e no input at the DTMF decoder. We used
10nf polyester capacitors instead of 470uf ceramic capacitors.
9. While testing the PCB we faced many problems which had the solution in proper
and tight connections with the PCB.
21. FORTNIGHT REPORT 5
Here we have found out the cost and quantity of the various components used in our
project.
Components used in a circuit :
ICs:
1. 89S52 ( 1 )
2. 8870 ( 1 )
3. APR9600 ( 1 )
4. 4047 ( 1 )
5. 6N139 ( 1 )
6. LM7805 ( 1 )
7. LM7812 ( 1 )
8. 7400 ( 1 )
9. MAX 232 ( 1 )
Crystal Oscillators:
1. 12 MHz ( 1 )
2. 3.474545 MHz ( 1 )
Transistors:
1. BC 547 ( 3 )
2. BC 516 ( 1 )
3. 2N2095 ( 1 )
Diodes:
1. IN4007 ( 5 )
2. IN4148 ( 3 )
3. Zenner diodes ( 3 )
4. LEDs ( 7 )
23. Cost of components:
ICs : Rs. 324
crystal oscillators: Rs. 108
Transistors: Rs. 81
Diodes: Rs. 45
Resistors: Rs. 37
Capacitors: Rs. 44
Transformer: Rs. 63
Other: Rs. 441
Cost of the circuit:
Cost of the components : Rs. 1143
Cost of the PCB : Rs. 1440
Labour cost :
*TOTAL COST : Rs. 2583
24. FORTNIGHT REPORT 6
Future Development
The primary PCB of our circuit has a very important application which can enhance its
real time operation. That is presence of the serial port for a serial communication with the
computer through COM ports. In this application the value of the number punched in by
the user is serially transmitted via MAX232 chip to the computer where it is processed
and a suitable wave file is triggered by a software program preferably written using
VISUAL BASICV6.0. the wave file which is played can be stored in the hard disk of the
computer and can be accessed by the program using the concept of uniform resource
locator (URL). Since the memory of the computer is huge a large number of speech
messages can be stored and played by a media player. The output from the computer can
be directly connected to the telephone line via audio transformer which is also called as
an isolation transformer.
The various nuances of serial communication is mentioned below:
Asynchronous mode of data transmission
In asynchronous transmissions, the link does not include a clock line because each end of
the link provides its own clock. Each transmitted byte includes a start bit to synchronize
the clocks followed by the eight bits of data (LSB first) and one or more stop bits to
signal the end of the transmitted word. The RS232 ports on PCs use asynchronous
formats to communicate with modems and other devices.
Data formats
Data bits in serial transmission may be in binary, hex or text format.
Binary data
With binary data, the receiver interprets a received byte as a binary number with a value
from 0 – 255. The bits are conventionally numbered 0 through 7 with each bit
representing the bit's value (0/1) multiplied by the power of two.
25. Text data
It is used in links which need to send messages or files containing text. A link may also
send binary data encoded as text. To send text the program uses a code that assigns a
numeric value to each text character. There are several coding conventions, ASCII being
the most common, which consists of 128 codes requiring only 7 data bit, and the 8th bit
may be a parity bit. The ASCII text format is used by Visual Basic's MSComm control.
ASCII HEX
We can use text to transfer binary data, by expressing the data in ASCII HEX format.
Each byte is represented by a pair of ASCII codes that represent the byte's two
hexadecimal characters. This format can represent any value using only the ASCII codes.
Instead of sending one byte to represent a value from 0 – 255 the sending device sends
two, one for each character in the HEX number that represents the byte. The receiving
computer treats it like ordinary text. After a computer receives the values it can process
or use the data any way it wants, including converting it back to binary data
RS 232 C Standard
RS-232 is a “complete” standard. This means that the standard sets out to ensure
compatibility between the host and peripheral systems by specifying
1) Common voltage and signal levels,
2) Common pin wiring configurations, and
3) A minimal amount of control information between the host and peripheral systems.
Unlike many standards which simply specify the electrical characteristics of a given
interface, RS-232 specifies electrical, functional, and mechanical characteristics in order
to meet the above three criteria.
Electrical Characteristics
The electrical characteristics section of the RS–232 standard includes specifications on
voltage levels, rate of change of signal levels, and line impedance.
Functional Characteristics
RS–232 has defined the function of the different signals that are used in the interface.
These signals are divided into four different categories: common, data, control, and
timing.
26. Mechanical Interface Characteristics
The third area covered by RS–232 concerns the mechanical interface. In particular, RS–
232 specifies a 25–pin connector. This is the minimum connector size that can
accommodate all of the signals defined in the functional portion of the standard.
Types of Connectors
VISUAL BASICS :
VB is preferred as the programming language because of its following features:
Based on basic language
Programming objects and events:
The visual forms and objects like list boxes and radio buttons that one uses on the
form, help to interact with the application in order to find out the flow of the
program. The forms and object perform specified action when an event occurs.
This is known as Event Driven Programming.
A quick and easy way to develop applications :
The tool provided by VB helps to reduce development time. It is faster to create
application using the tools available.
A quick editing, testing and debugging.
Full array of mathematical string handling and graphic functions.
Sequential and random access files support.
Powerful database access tools.
27. Internet features.
ActiveX support.
Package and deployment wizard makes distributing the application samples.
