CHAPTER 1 INTRODUCTION One of the main form of communication that has been in use since 19 th century is Radio Wave communication. Radio Waves have found its place in each and every field whether it be medical, electronics or space. In general it exists in every system in one or the other form. The use of Radio Waves had made life much simpler and safer. A heart patient can be monitored by a doctor remotely sitting in his chamber is because of the use of Radio Waves. Radio Waves have made communication through telephone, internet etc easier and cheaper. Our project demonstrate one such example were Radio Wave is employed in a way which is helpful to us. This project is designed and developed for helping the passengers traveling in train and bus especially during night. The people who are not aware of the station on which one should get down will find this very helpful. Here the station name is displayed and announced 1
RF based station name display in train compartment
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
CHAPTER 1
INTRODUCTION
One of the main form of communication that has been in use since 19 th
century is Radio Wave communication. Radio Waves have found its place in each
and every field whether it be medical, electronics or space. In general it exists in
every system in one or the other form.
The use of Radio Waves had made life much simpler and safer. A heart
patient can be monitored by a doctor remotely sitting in his chamber is because of
the use of Radio Waves. Radio Waves have made communication through
telephone, internet etc easier and cheaper.
Our project demonstrate one such example were Radio Wave is employed in
a way which is helpful to us. This project is designed and developed for helping
the passengers traveling in train and bus especially during night. The people who
are not aware of the station on which one should get down will find this very
helpful. Here the station name is displayed and announced simultaneously when
the station is about to reach which can assist both literate and illiterate.
The RF technology is used in the project to communicate between the
transmitter and receiver. Each transmitter has a unique binary code which is
transmitted continuously to space in a particular range. This signal is captured by
the receiver when it reaches in its range. So in the case of a train, the transmitter
placed in the station is detected by the receiver in the train and the binary code is
processed to give out the station name display and audio corresponding to the
binary code in the receiver. A LCD unit is used for displaying the station name and
a speaker is used for the announcement.
1
1.1. BLOCK DIAGRAM
The block diagram consists of the transmitter and receiver section. They can
be represented as the following block diagrams.
1.1.1. Transmitter
Fig. 1.1 Block Diagram of Transmitter Module
The block diagram of the transmitter is given in fig. 1.1. The main parts in
the transmitter are:
1. Power Supply
The power supply section is the section which provide +5V for the
transmitter section to work. IC LM7805 is used for providing a constant
power of +5V.
2. Encoder
This section contains the identity of the transmitter. An encoder can be a
device used to change a signal (such as a bit stream) or data into a code.
The code serves any of a number of purposes such as compressing
information for transmission or storage, encrypting or adding
redundancies to the input code etc.
2
3. RF Transmitter
This section transmits the binary data to space in a particular range based
on the antenna used. This signal is received by the receiver and it
compares the binary code to find the corresponding station name from
the database.
1.1.2. Receiver
Fig. 1.2 Block Diagram of Receiver Module
1. Power Supply
The power supply section is the section which provide +5V for the
transmitter section to work. IC LM7805 is used for providing a constant
power of +5V.
3
2. Decoder
A decoder is a device which does the reverse of the encoder, undoing the
encoding so that the original information can be retrieved.
3. Microcontroller
Unlike microprocessors, microcontrollers are generally optimized for
specific applications. As a result the peripherals can be simplified and
reduced which cuts down the production cost.
4. RF Receiver
The RF signal transmitted by the transmitter is detected and received by
this section of the receiver. This binary encoder data is sent to the
decoder for decoding the original data.
5. LCD
This is the output unit in the receiver section. The station name is
displayed on this display unit when the receiver comes in the range of the
transmitter.
6. Voice Alert
This is another output unit in the receiver. This gives the voice alert of
the station reached based on the RF transmitter signal received.
4
CHAPTER 2
PROJECT DESCRIPTION
2.1. INTRODUCTION
RF based station name intimation is based traditionally on RF signal. RF
signal at the frequency range 434 MHz is employed for communication between
transmitter unit and receiver unit in our project.
Each station is identified by a unique binary code, for example, 001 for
Chennai and 100 for Nagerkoil. This binary code is transmitted by transmitter
module continuously at a frequency range of 434 MHz within a distance of 400
foot outdoor and 200 foot indoor. This distance can be enhanced by using
additional RF antenna.
When the receiver comes within the range of transmitter, it receives the data
from the transmitter in the form of RF signal which is further decoded to collect
the binary code and display the station name along with the voice play back.
2.2. TRANSMITTER MODULE
Transmitter section is the smallest section having few components which
include:
1. RF transmitter TWS-434 A
2. Encoded HT-12 E
3. Voltage Regulator LM7805.
LM7805 assures a constant supply of +5 V for the transmitter module. This
voltage of +5 V is used to drive transmitter and encoder.
5
2.2.1. Circuit Description
The third pin of TWS-434 A, RF transmitter and 18 th pin of Encoder HT-12
E is connected to the output pin of Voltage Regulator LM7805 which drive the
circuit with a constant voltage of 5V.
The first pin of TWS-434 A and all the address bus are connected to second pin of
LM7805 which represent ground. The first pin of voltage regulator receives a
voltage of 9V from a battery source.
The other connection include a connection between the Dout (7th pin) of HT-
12 E and the data pin (2nd pin) of TWS-434 A.
2.2.2. Working Principle
The binary values unique to each station are assigned by the encoder HT-
12 E. Each address/data input can be set to the logic state 0 or 1.
Grounding the pin is taken as 0 while 1 can be achieved by giving 5V or
leaving the pins open (No connection). So in order to get a binary value of 0001
only one pin is pulled high i.e. 13th pin (D11) is pulled high while pins 10, 11 and
12 are grounded to represent logical zero.
On receipt of transmit enable i.e. TE-active (14th pin) is pulled low. The data
which is here is the binary value is fed as input to the transmitter TWS-434 A from
Dout (17th pin) along with header bits.
Received data from HT-12 E encoder is amplitude modulated and
transmitted at a frequency range of 433.92 MHz.
6
Fig. 2.1 Transmitter Module
7
2.3. RECEIVER MODULE
Receiver is the output section of the project. Receiver module includes the
following components:
1. RF Receiver RWS-434 A
2. Microcontroller 89C51 which is regarded as the brain of the circuit.
3. LCD module for display the station name
4. Audio playback IC APR 9600
5. Power supply section which contains transformer, rectifier, filter, regulator
which ensures a constant +5V.
Main function of the receiver unit is to detect the RF signal transmitted by
the TWS-434A and give the response according to the received data from the
receiver. Varies components of the receiver unit has its own function.RWS-434
receives the RF signal, AT 89C51 processes the input data and produces a
corresponding response, LCD module considered as the output unit displays the
processed data from the microprocessor, APR 9600 gives the output in the form of
audio playback which is stored in the internal memory of the IC.
8
9
2.3.1. Circuit Description
A constant voltage of +5V is applied to the 4th and 5th pin of the receiver, 2nd
pin of the LCD module, 40th pin of Microcontroller 89C51, 18th pin of the decoded
IC HT-12D and various pins of APR 9600 as shown in figure below through
voltage regulator LM7805. It derives its input voltage from bridge rectifier. The 8
bit data pins D0 - D7 are used to send information from port 2 of the
microcontroller to the LCD. RS (register select) is one of the important registers
inside the LCD. The RS pin is used for their selection as follows. If RS=0, the
instruction code register is selected, allowing the user to send a command such as
clear display, cursor at home, etc. if RS=1 the data register is selected, allowing the
user to send data to be displayed on the LCD.R/W input pin of LCD allows the
user to write information to the LCD or read information from it. R/W=1 when
reading; R/W=0 when writing. E (enable) the enable pin is used by the LCD to
latch information presented on its data pins. When data is supplied to data pins, a
high to low pulse must be applied to this pin in order for the LCD to latch in the
data present at the data pins. These 3 pins (RS, RW, and E) of LCD are connected
to the 89C51 through port 0. The communication between AT 89C51 and audio IC
APR 9600 is through address/data bus of port 0 of 89C51 and pin 1 and pin 2
namely M1 and M2 of APR 9600. Microcontroller receives data from decoder HT-
12 D through port 1 which is an 8 bit bidirectional I/O port from the output data
pins D8-D11 of HT-12 D.
The receiver RWS-434 is connected to decoder such that the received RF
signal is fed as input to the data input pin Din (pin 14) of the decoder from 2nd pin
of the receiver.
10
2.3.2. Working Principle
When the receiver unit comes in the range of transmitter unit which
continuously transmit RF signal, the whole receiver unit gets activated. The
receiver unit receives the RF signal at a frequency range of 434 MHz which
actually is a digital data which includes the binary code assigned to the particular
transmitter which denotes a station and a carrier signal. Digital output is taken
from pin 2 of RWS-434 and received by decoder HT-12 D through data input pin
(18th pin). The received serial input data are compared three times continuously
with the local address. If no error or unmatched codes are found, the input codes
are decoded and then transferred to the output pins. The VT (Valid Transmission)
pin (12th pin) gives high to indicate a valid transmission.
The decoded signal is given as data input to AT 89C51 at port 1. On receipt
of the binary code microcontroller which act as a database of station name,
compares the received binary code with its stored binary code, on no error or
unmatched code the station name corresponding to the binary code is displayed on
the LCD screen along with a voice alert from APR 9600.
The whole cycle will be repeated when the receiver receives a new set of
binary code transmitted by some other transmitter denoting a different station. The
display will be active only for pre defined duration, after which the LCD return to
its ideal state. The data to be displayed on the LCD screen is available at port 2 and
control of the register of the LCD is through port 3.
11
CHAPTER 3
HARDWARE DESCRIPTION
3.1. RF TRANSMITTER
The function of a radio frequency (RF) transmitter is to modulate, up
convert, and amplify signals for transmission into free space. An RF transmitter
generally includes a modulator that modulates an input signal and a radio
frequency power amplifier that is coupled to the modulator to amplify the
modulated input signal. The radio frequency power amplifier is coupled to an
antenna that transmits the amplified modulated input signal.
The RF transmitter used in our project is TWS-434A. This RF transmitter
transmits data in the frequency range of 433.92 MHz with a range of
approximately 400 foot (open area) outdoors. Indoors, the range is approximately
200 foot, and will go through most walls. TWS-434A has features which includes
small in size, low power consumption i.e. 8mW and operate from 1.5 to 12 Volts-
DC, excellent for applications requiring short-range RF signal. Data to be send is
Amplitude modulation with the carrier RF signal.
Fig. 3.1 RF Transmitter
12
3.1.1. Pin Description of Transmitter
PIN 1: GROUND (-5V)
PIN2: INPUT PIN FOR DATA FROM ENCODER
PIN3: SUPPLY (+5V)
PIN 4: PIN FOR EXTERNAL RF ANTENNA
3.2. RF RECEIVER
The RF receiver receives an RF signal, converts the RF signal to an IF
signal, and then converts the IF signal to a base band signal, which it then provides
to the base band processor. As is also known, RF transceivers typically include
sensitive components susceptible to noise and interference with one another and
with external sources. The RF receiver is coupled to the antenna and includes a low
noise amplifier, one or more intermediate frequency stages, a filtering stage, and a
data recovery stage. The low noise amplifier receives an inbound RF signal via the
antenna and amplifies it.
The RF receiver used is RWS-434. This RF receiver receives RF signal
which is in the frequency of 434.92 MHz and has a sensitivity of 3uV. The RWS-
434 receiver operates from 4.5 to 5.5 volts-DC, and has both linear and digital
outputs and its tunable to match the frequency of the transmitter unit.
13
Fig. 3.2 RF Receiver
3.2.1. Pin Description of Receiver
PIN1: GROUND (-5V)
PIN2: OUTPUT PIN FOR DIGITAL DATA RECIEVED
PIN 3: OUTPUT PIN FOR ANALOG DATA RECIEVED
PIN4: SUPPLY (+5V)
PIN5: SUPPLY (+5V)
PIN6: GROUND (-5V)
PIN7: GROUND (-5V)
PIN 8: PIN FOR EXTERNAL RF ANTENNA
14
3.3. ENCODER
An encoder can be a device used to change a signal (such as a bit stream) or
data into a code. The code serves any of a number of purposes such as compressing
information for transmission or storage, encrypting or adding redundancies to the
input code, or translating from one code to another. This is usually done by means
of a programmed algorithm, especially if any part is digital, while most analog
encoding is done with analog circuitry. Encoder used here is HT 12E. The HT12E
encoder is a CMOS IC It is capable of encoding 8 bits of address (A0-A7) and 4-
bits of data (AD8-AD11) information. Each address/data input can be set to one of
the two logic states, 0 or 1. Grounding the pins is taken as a 0 while a high can be
given by giving +5V or leaving the pins open (no connection). Upon reception of
transmit enable (TE-active low), the programmed address/data are transmitted
together with the header bits via an RF medium.
Fig. 3.3 Encoder
15
3.3.1. Pin Description of Encoder
Table. 3.1 Pin Description of Encoder
Pin
Name
I/O
Internal
Connection Description
A0~A7 I
CMOS IN
Pull-high
Input pins for address A0~A7 setting
These pins can be externally set to VSS or
left open
NMOS
TRANSMISSI
ON GATE
PROTECTION
DIODE
(HT12E)
AD8~A
D11
I
NMOS
TRANSMISSI
ON GATE
PROTECTION
DIODE
(HT12E)
Input pins for address/data AD8~AD11
setting
These pins can be externally set to VSS or
left open
D8~D11 I
CMOS IN
Pull-High
Input pins for data D8~D11 setting and
transmission en- able, active low
These pins should be externally set to VSS
or left open
DOUT O CMOS OUT Encoder data serial transmission output
16
L/MB I CMOS IN
Pull-high
Latch/Momentary transmission format
selection pin: Latch: Floating or VDD
Momentary: VSS
TE I
CMOS IN
Pull-high Transmission enable, active low (see Note)
OSC1 I OSCILLATOR
1
Oscillator input pin
OSC2 O OSCILLATOR
1
Oscillator output pin
X1 I OSCILLATOR
2
455kHz resonator oscillator input
X2 O OSCILLATOR
2
455kHz resonator oscillator output
VSS I Negative power supply, grounds
VDD I Positive power supply
3.4. DECODER
A decoder is a device which does the reverse of an encoder, undoing the
encoding so that the original information can be retrieved. The same method used
to encode is usually just reversed in order to decode. In digital electronics this
would mean that a decoder is a multiple-input, multiple-output logic circuit that
converts coded inputs into coded outputs. Enable inputs must be on for the decoder
to function, otherwise its outputs assume a single "disabled" output code word.
17
Decoding is necessary in applications such as data multiplexing, 7 segment display
and memory address decoding. The decoder used here is HT 12D. The HT12D is a
decoder IC made especially to pair with the HT 12E encoder. It is a CMOS IC. The
decoder is capable of decoding 8 bits of address (A0 - A7) and 4 bits of data (AD8
- AD11) information. For proper operation, a pair of encoder/decoder with the
same number of addresses and data format should be chosen. The decoders receive
serial addresses and data from programmed encoders that are transmitted by a
carrier using an RF or an IR transmission medium. They compare the serial input
data three times continuously with their local addresses. If no error or unmatched
codes are found, the input data codes are decoded and then transferred to the output
pins. The VT pin also goes high to indicate a valid transmission. The decoders are
capable of decoding information that consists of N bits of address and 12_N bits of
data. Of this series, the HT 12D is arranged to provide 8 address bits and 4 data
bits.
18
Fig. 3.4 Decoder
3.4.1. Pin Description of Decoder
Table. 3.2 Pin Description of Decoder
Pin
Name
I/O
Internal
Connection Description
A0~A7
(HT12D)
NMOS
Transmission
Gate
Input pins for address A0~A7 setting
These pins can be externally set to VSS
or left open.
19
D8~D11
(HT12D)
O CMOS OUT Output data pins, power-on state is
low.
DIN I CMOS IN Serial data input pin
VT O CMOS OUT Valid transmission, active high
OSC1 I Oscillator Oscillator input pin
OSC2 O Oscillator Oscillator output pin
VSS Negative power supply, ground
VDD Positive power supply
3.5. LCD MODULE
A liquid crystal display (LCD) is an electronically-modulated optical device
shaped into a thin, flat panel made up of any number of color or monochrome
pixels filled with liquid crystals and arrayed in front of a light source (backlight) or
reflector. It is often utilized in battery-powered electronic devices because it uses
very small amounts of electric power. LCD has material which combines the
properties of both liquids and crystals. Rather than having a melting point, they
have a temperature range within which the molecules are almost as mobile as they
would be in a liquid, but are grouped together in an ordered form similar to a
crystal.
20
LCD consists of two glass panels, with the liquid crystal materials
sandwiched in between them. The inner surface of the glass plates is coated with
transparent electrodes which define in between the electrodes and the crystal,
which makes the liquid crystal molecules to maintain a defined orientation angle.
When a potential is applied across the cell, charge carriers flowing through the
liquid will disrupt the molecular alignment and produce turbulence. When the
liquid is not activated, it is transparent. When the liquid is activated the molecular
turbulence causes light to be scattered in all directions and the cell appears to be
bright. Thus the required message is displayed.
When the LCD is in the off state, the two polarizers and the liquid crystal
rotate the light rays, such that they come out of the LCD without any orientation,
and hence the LCD appears transparent. When sufficient voltage is applied to the
electrodes the liquid crystal molecules would be aligned in a specific direction. The
light rays passing through the LCD would be rotated by the polarizer, which would
result in activating/highlighting the desired characters. The power supply should be
of +5v, with maximum allowable transients of 10mv.
To achieve a better/suitable contrast for the display the voltage (VL) at pin 3
should be adjusted properly. A module should not be removed from a live circuit.
The ground terminal of the power supply must be isolated properly so that voltage
is induced in it. The module should be isolated properly so that stray voltages are
not induced, which could cause a flicking display. LCD is lightweight with only a
few, millimeters thickness since the LCD consumes less power, they are
compatible with low power electronic circuits, and can be powered for long
durations. LCD does not generate light and so light is needed to read the display.
By using backlighting, reading is possible in the dark. LCDs have long life and a
wide operating temperature range. Before LCD is used for displaying proper
initialization should be done.
21
LCDs with a small number of segments, such as those used in digital
watches and pocket calculators, have individual electrical contacts for each
segment. An external dedicated circuit supplies an electric charge to control each
segment. This display structure is unwieldy for more than a few display elements.
Small monochrome displays such as those found in personal organizers, or older
laptop screens have a passive-matrix structure employing super-twisted nematic
(STN) or double-layer STN (DSTN) technology—the latter of which addresses a
color-shifting problem with the former—and color-STN (CSTN)—wherein color is
added by using an internal filter.
Each row or column of the display has a single electrical circuit. The pixels
are addressed one at a time by row and column addresses. This type of display is
called passive-matrix addressed because the pixel must retain its state between
refreshes without the benefit of a steady electrical charge. As the number of pixels
(and correspondingly, columns and rows) increases, this type of display becomes
less feasible. Very slow response times and poor contrast are typical of passive
matrix addressed LCDs.
High-resolution color displays such as modern LCD computer monitors and
televisions use an active matrix structure. A matrix of thin-film transistors (TFTs)
is added to the polarizing and color filters. Each pixel has its own dedicated
transistor, allowing each column line to access one pixel. When a row line is
activated, all of the column lines are connected to a row of pixels and the correct
voltage is driven onto all of the column lines. The row line is then deactivated and
the next row line is activated. All of the row lines are activated in sequence during
a refresh operation. Active-matrix addressed displays look "brighter" and "sharper"
than passive-matrix addressed displays of the same size, and generally have
quicker response times, producing much better images.
22
A general purpose alphanumeric LCD, with two lines of 16 characters. So
the type of LCD used in this project is16 characters * 2 lines with 5*7 dots with
cursor, built in controller, +5v power supply, 1/16 duty cycle.
3.5.1. LCD Layout
Fig. 3.5 LCD Layout
3.5.2. Pin Description of LCD Module
Table. 3.3 Pin Description of LCD Module
23
3.6. VOICE MODULE
APR9600 device to reproduce voice signals in their natural form. It
eliminates the need for encoding and compression, which often introduce
distortion. The APR9600 device offers true single-chip voice recording, non-
volatile storage, and playback capability for 40 to 60 seconds. The device supports
both random and sequential access of multiple messages. Sample rates are user-
selectable, allowing designers to customize their design for unique quality and
storage time needs. Integrated output amplifier, microphone amplifier, and AGC
circuits greatly simplify system design. The device is ideal for use in portable
voice recorders, toys, and many other consumer and industrial applications.
APLUS integrated achieves these high levels of storage capability by using its
proprietary analog/multilevel storage technology implemented in an advanced
Flash non-volatile memory process, where each memory cell can store 256 voltage
levels. This technology enables the APR9600 device to reproduce voice signals in
their natural form. It eliminates the need for encoding and compression, which
often introduce distortion.
24
3.6.1. Pin Diagram of APR 9600
Fig. 3.6 Pin Diagram of APR 9600
3.6.2. Pin Description of APR 9600
Table. 3.4 Pin Description of APR 9600
Pin Name Functions Pin Mane Functions1 -M1 Select 1st section of sound