Download Wireless Music transmission and reception by IR communication

WK130
WIRELESS MUSIC TRANSMISSION AND
RECEPTION BY IR COMMUNICATION
Wireless Music transmission and reception by IR communication
WK130
INDEX
1.
ABSTRACT
2.
BLOCK DIAGRAM
3.
HARDWARE EXPLNATION
4.
MELODY GENERATOR
5.
IR
6.
TRANSISTOR DRIVER CIRCUIT
7.
SIREN
8.
APPLICATIONS
9.
ADVANTAGES
10. CONCLUSION
11. REFERENCES
Wireless Music transmission and reception by IR communication
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ABSTRACT
Wireless Music transmission and reception by IR communication
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ABSTRACT:
By using this project audio musical notes can be generated and heard up to a distance of
10 meters. The circuit can be divided into two parts: IR music transmitter and receiver.
The IR music transmitter works off a 9V battery, while the IR music receiver works off
regulated 9V to 12V. The transmitter uses popular melody generator IC UM66 that can
continuously generate musical tones. The output of this music melody generator is fed to
the IR driver stage to get the maximum range.
An LED is connected in the Transmitter section. This LED flickers according to the
musical tones generated by UM66 IC, indicating modulation. Two IR LEDs are
connected in series. For maximum sound transmission these should be oriented towards
IR phototransistor L14F1. The IR music receiver uses popular op-amp IC μA741 and
audio-frequency amplifier IC LM386 along with phototransistor L14F1 and some
discrete components. The melody generated by IC UM66 is transmitted through IR
LEDs, received by phototransistor and fed to pin 2 of IC μA741. Its gain can be varied
using potentiometer VR1. The output
of IC μA741 is fed to IC LM386 via capacitor C5 and potentiometer. The melody
produced is heard through the receiver’s loudspeaker. Potentiometer VR2 is used to
control the volume of loudspeaker (8-ohm, 1W). Switching off the power supply stops
melody generation.
This project uses regulated 9V, 750mA power supply. 7805 three terminal voltage
regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify
the ac out put of secondary of 230/18V step down transformer.
Wireless Music transmission and reception by IR communication
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Transmitter: Wireless Music transmission and reception by IR communication
LED Music
flicker indicator
Melody
Generator
3.3V
regulator
Transistor Driver
Stage - I
Transistor Driver
Stage - II
IR LED
Step
down
T/F
Bridge
Rectifier
Filter
Circuit
Regulator
Power supply to all sections
Wireless Music transmission and reception by IR communication
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Receiver: Wireless Music transmission and reception by IR communication
Gain control
Photo
Transistor
Audio Amplifier
Stage - I
Gain control
Audio Amplifier
Stage - II
Loud speaker
Step
down
T/F
Bridge
Rectifier
Filter
Circuit
Regulator
Power supply to all sections
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HARDWARE EXPLANATION
Wireless Music transmission and reception by IR communication
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Hardware Explanation:
RESISTOR:
Resistors "Resist" the flow of electrical current. The higher the value of resistance
(measured in ohms) the lower the current will be. Resistance is the property of a
component which restricts the flow of electric current. Energy is used up as the voltage
across the component drives the current through it and this energy appears as heat in the
component.
Colour Code:
Wireless Music transmission and reception by IR communication
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CAPACITOR:
Capacitors
store
electric
charge.
They
are
used
with
resistors
in timing circuits because it takes time for a capacitor to fill with charge. They are used
to smooth varying DC supplies by acting as a reservoir of charge. They are also used in
filter circuits because capacitors easily pass AC (changing) signals but they block DC
(constant) signals.
Circuit symbol:
Electrolytic capacitors are polarized and they must be connected the correct way
round, at least one of their leads will be marked + or -.
Examples:
DIODES:
Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol
shows the direction in which the current can flow. Diodes are the electrical version of a
valve and early diodes were actually called valves.
Circuit symbol:
Diodes must be connected the correct way round, the diagram may be
labeled a or + for anode and k or - for cathode (yes, it really is k, not c, for cathode!). The
cathode is marked by a line painted on the body. Diodes are labeled with their code in
small print; you may need a magnifying glass to read this on
small signal diodes.
Wireless Music transmission and reception by IR communication
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Example:
LIGHT-EMITTING DIODE (LED):
The longer lead is the anode (+) and the shorter lead is the cathode (&minus). In the
schematic symbol for an LED (bottom), the anode is on the left and the cathode is on the
right. Lighemitting diodes are elements for light signalization in electronics.
They are manufactured in different shapes, colors and sizes. For their low price,
low consumption and simple use, they have almost completely pushed aside other light
sources- bulbs at first place.
Wireless Music transmission and reception by IR communication
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It is important to know that each diode will be immediately destroyed unless its current is
limited. This means that a conductor must be connected in parallel to a diode. In order to
correctly determine value of this conductor, it is necessary to know diode’s voltage drop
in forward direction, which depends on what material a diode is made of and what colors
it is. Values typical for the most frequently used diodes are shown in table below: As
seen, there are three main types of LEDs. Standard ones get full brightness at current of
20mA. Low Current diodes get full brightness at ten time’s lower current while Super
Bright diodes produce more intensive light than Standard ones.
Since the 8052 microcontrollers can provide only low input current and since their
pins are configured as outputs when voltage level on them is equal to 0, direct
confectioning to LEDs is carried out as it is shown on figure (Low current LED, cathode
is connected to output pin).
Switches and Pushbuttons:
A push button switch is used to either close or open an electrical circuit depending
on the application. Push button switches are used in various applications such as
industrial equipment control handles, outdoor controls, mobile communication terminals,
and medical equipment, and etc. Push button switches generally include a push button
disposed within a housing. The push button may be depressed to cause movement of the
push button relative to the housing for directly or indirectly changing the state of an
electrical contact to open or close the contact. Also included in a pushbutton switch may
be an actuator, driver, or plunger of some type that is situated within a switch housing
having at least two contacts in communication with an electrical circuit within which the
switch is incorporated.
Wireless Music transmission and reception by IR communication
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Typical actuators used for contact switches include spring loaded force cap actuators
that reciprocate within a sleeve disposed within the canister. The actuator is typically
coupled to the movement of the cap assembly, such that the actuator translates in a
direction that is parallel with the cap. A push button switch for a data input unit for a
mobile communication device such as a cellular phone, a key board for a personal
computer or the like is generally constructed by mounting a cover member directly on a
circuit board. Printed circuit board (PCB) mounted pushbutton switches are an
inexpensive means of providing an operator interface on industrial control products. In
such push button switches, a substrate which includes a plurality of movable sections is
formed of a rubber elastomeric. The key top is formed on a top surface thereof with a
figure, a character or the like by printing, to thereby provide a cover member. Push button
switches incorporating lighted displays have been used in a variety of applications. Such
switches are typically comprised of a pushbutton, an opaque legend plate, and a back
light to illuminate the legend plate.
Block Diagram For Regulated Power Supply (RPS):
Figure: Power Supply
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Description :
Transformer
A transformer is a device that transfers electrical energy from one circuit to another
through inductively coupled conductors—the transformer's coils. A varying current in the
first or primary winding creates a varying magnetic flux in the transformer's core, and
thus a varying magnetic field through the secondary winding. This varying magnetic field
induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This
effect is called mutual induction.
Figure: Transformer Symbol
(or)
Transformer is a device that converts the one form energy to another form of energy like
a transducer.
Wireless Music transmission and reception by IR communication
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Figure: Transformer
Basic Principle
A transformer makes use of Faraday's law and the ferromagnetic properties of an iron
core to efficiently raise or lower AC voltages. It of course cannot increase power so that
if the voltage is raised, the current is proportionally lowered and vice versa.
Figure: Basic Principle
Transformer Working
Wireless Music transmission and reception by IR communication
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A transformer consists of two coils (often called 'windings') linked by an iron core, as
shown in figure below. There is no electrical connection between the coils; instead they
are linked by a magnetic field created in the core.
Figure: Basic Transformer
Transformers are used to convert electricity from one voltage to another with minimal
loss of power. They only work with AC (alternating current) because they require a
changing magnetic field to be created in their core. Transformers can increase voltage
(step-up) as well as reduce voltage (step-down).
Alternating current flowing in the primary (input) coil creates a continually changing
magnetic field in the iron core. This field also passes through the secondary (output) coil
and the changing strength of the magnetic field induces an alternating voltage in the
secondary coil. If the secondary coil is connected to a load the induced voltage will make
an induced current flow. The correct term for the induced voltage is 'induced
electromotive force' which is usually abbreviated to induced e.m.f.
The iron core is laminated to prevent 'eddy currents' flowing in the core. These are
currents produced by the alternating magnetic field inducing a small voltage in the core,
just like that induced in the secondary coil. Eddy currents waste power by needlessly
heating up the core but they are reduced to a negligible amount by laminating the iron
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because this increases the electrical resistance of the core without affecting its magnetic
properties.
Transformers have two great advantages over other methods of changing voltage:
1. They provide total electrical isolation between the input and output, so they can
be safely used to reduce the high voltage of the mains supply.
2. Almost no power is wasted in a transformer. They have a high efficiency (power
out / power in) of 95% or more.
Wireless Music transmission and reception by IR communication
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Classification of Transformer
 Step-Up Transformer
 Step-Down Transformer
Step-Down Transformer
Step down transformers are designed to reduce electrical voltage. Their primary voltage
is greater than their secondary voltage. This kind of transformer "steps down" the voltage
applied to it. For instance, a step down transformer is needed to use a 110v product in a
country with a 220v supply.
Step down transformers convert electrical voltage from one level or phase configuration
usually down to a lower level. They can include features for electrical isolation, power
distribution, and control and instrumentation applications. Step down transformers
typically rely on the principle of magnetic induction between coils to convert voltage
and/or current levels.
Step down transformers are made from two or more coils of insulated wire wound around
a core made of iron. When voltage is applied to one coil (frequently called the primary or
input) it magnetizes the iron core, which induces a voltage in the other coil, (frequently
called the secondary or output). The turn’s ratio of the two sets of windings determines
the amount of voltage transformation.
Figure: Step-Down Transformer
Wireless Music transmission and reception by IR communication
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An example of this would be: 100 turns on the primary and 50 turns on the secondary, a
ratio of 2 to 1.
Step down transformers can be considered nothing more than a voltage ratio device.
With step down transformers the voltage ratio between primary and secondary will mirror
the "turn’s ratio" (except for single phase smaller than 1 kva which have compensated
secondary). A practical application of this 2 to 1 turn’s ratio would be a 480 to 240
voltage step down. Note that if the input were 440 volts then the output would be 220
volts. The ratio between input and output voltage will stay constant. Transformers should
not be operated at voltages higher than the nameplate rating, but may be operated at
lower voltages than rated. Because of this it is possible to do some non-standard
applications using standard transformers.
Single phase step down transformers 1 kva and larger may also be reverse connected to
step-down or step-up voltages. (Note: single phase step up or step down transformers
sized less than 1 KVA should not be reverse connected because the secondary windings
have additional turns to overcome a voltage drop when the load is applied. If reverse
connected, the output voltage will be less than desired.)
Step-Up Transformer
A step up transformer has more turns of wire on the secondary coil, which makes a larger
induced voltage in the secondary coil. It is called a step up transformer because the
voltage output is larger than the voltage input.
Step-up transformer 110v 220v design is one whose secondary voltage is greater than its
primary voltage. This kind of transformer "steps up" the voltage applied to it. For
instance, a step up transformer is needed to use a 220v product in a country with a 110v
supply.
A step up transformer 110v 220v converts alternating current (AC) from one voltage to
another voltage. It has no moving parts and works on a magnetic induction principle; it
Wireless Music transmission and reception by IR communication
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can be designed to "step-up" or "step-down" voltage. So a step up transformer increases
the voltage and a step down transformer decreases the voltage.
The primary components for voltage transformation are the step up transformer core and
coil. The insulation is placed between the turns of wire to prevent shorting to one another
or to ground. This is typically comprised of Mylar, nomex, Kraft paper, varnish, or other
materials. As a transformer has no moving parts, it will typically have a life expectancy
between 20 and 25 years.
Figure: Step-Up Transformer
Applications :
Generally these Step-Up Transformers are used in industries applications only.
Types of Transformer
Mains Transformers
Mains transformers are the most common type. They are designed to reduce the AC
mains supply voltage (230-240V in the UK or 115-120V in some countries) to a safer
low voltage. The standard mains supply voltages are officially 115V and 230V, but 120V
and 240V are the values usually quoted and the difference is of no significance in most
cases.
Wireless Music transmission and reception by IR communication
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Figure: Main Transformer
To allow for the two supply voltages mains transformers usually have two separate
primary coils (windings) labeled 0-120V and 0-120V. The two coils are connected in
series for 240V (figure 2a) and in parallel for 120V (figure 2b). They must be wired the
correct way round as shown in the diagrams because the coils must be connected in the
correct sense (direction):
Most mains transformers have two separate secondary coils (e.g. labeled 0-9V, 0-9V)
which may be used separately to give two independent supplies, or connected in series to
create a center-tapped coil (see below) or one coil with double the voltage.
Some mains transformers have a centre-tap halfway through the secondary coil and they
are labeled 9-0-9V for example. They can be used to produce full-wave rectified DC with
just two diodes, unlike a standard secondary coil which requires four diodes to produce
full-wave rectified DC.
Wireless Music transmission and reception by IR communication
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A mains transformer is specified by:
1. Its secondary (output) voltages Vs.
2. Its maximum power, Pmax, which the transformer can pass, quoted in VA (voltamp). This determines the maximum output (secondary) current, Imax...
...where Vs is the secondary voltage. If there are two secondary coils the
maximum power should be halved to give the maximum for each coil.
3. Its construction - it may be PCB-mounting, chassis mounting (with solder tag
connections) or toroidal (a high quality design).
Audio Transformers
Audio transformers are used to convert the moderate voltage, low current output of an
audio amplifier to the low voltage, high current required by a loudspeaker. This use is
called 'impedance matching' because it is matching the high impedance output of the
amplifier to the low impedance of the loudspeaker.
Figure: Audio transformer
Radio Transformers
Radio transformers are used in tuning circuits. They are smaller than mains and audio
transformers and they have adjustable ferrite cores made of iron dust. The ferrite cores
can be adjusted with a non-magnetic plastic tool like a small screwdriver. The whole
transformer is enclosed in an aluminum can which acts as a shield, preventing the
transformer radiating too much electrical noise to other parts of the circuit.
Wireless Music transmission and reception by IR communication
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Figure: Radio Transformer
Turns Ratio and Voltage
The ratio of the number of turns on the primary and secondary coils determines the ratio
of the voltages...
...where Vp is the primary (input) voltage, Vs is the secondary (output) voltage, Np is the
number of turns on the primary coil, and Ns is the number of turns on the secondary coil.
Diodes
Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol
shows the direction in which the current can flow. Diodes are the electrical version of a
valve and early diodes were actually called valves.
Figure: Diode Symbol
Wireless Music transmission and reception by IR communication
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A diode is a device which only allows current to flow through it in one direction. In this
direction, the diode is said to be 'forward-biased' and the only effect on the signal is that
there will be a voltage loss of around 0.7V. In the opposite direction, the diode is said to
be 'reverse-biased' and no current will flow through it.
Rectifier
The purpose of a rectifier is to convert an AC waveform into a DC waveform (OR)
Rectifier converts AC current or voltages into DC current or voltage. There are two
different rectification circuits, known as 'half-wave' and 'full-wave' rectifiers. Both use
components called diodes to convert AC into DC.
The Half-wave Rectifier
The half-wave rectifier is the simplest type of rectifier since it only uses one diode, as
shown in figure.
Figure: Half Wave Rectifier
Figure 2 shows the AC input waveform to this circuit and the resulting output. As you
can see, when the AC input is positive, the diode is forward-biased and lets the current
through. When the AC input is negative, the diode is reverse-biased and the diode does
not let any current through, meaning the output is 0V. Because there is a 0.7V voltage
loss across the diode, the peak output voltage will be 0.7V less than Vs.
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Figure: Half-Wave Rectification
While the output of the half-wave rectifier is DC (it is all positive), it would not be
suitable as a power supply for a circuit. Firstly, the output voltage continually varies
between 0V and Vs-0.7V, and secondly, for half the time there is no output at all.
The Full-wave Rectifier
The circuit in figure 3 addresses the second of these problems since at no time is the
output voltage 0V. This time four diodes are arranged so that both the positive and
negative parts of the AC waveform are converted to DC. The resulting waveform is
shown in figure 4.
Wireless Music transmission and reception by IR communication
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Figure: Full-Wave Rectifier
Figure: Full-Wave Rectification
When the AC input is positive, diodes A and B are forward-biased, while diodes C and D
are reverse-biased. When the AC input is negative, the opposite is true - diodes C and D
are forward-biased, while diodes A and B are reverse-biased.
While the full-wave rectifier is an improvement on the half-wave rectifier, its output still
isn't suitable as a power supply for most circuits since the output voltage still varies
between 0V and Vs-1.4V. So, if you put 12V AC in, you will 10.6V DC out.
Capacitor Filter
The capacitor-input filter, also called "Pi" filter due to its shape that looks like the
Greek letter pi, is a type of electronic filter. Filter circuits are used to remove unwanted or
undesired frequencies from a signal.
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Figure: Capacitor Filter
A typical capacitor input filter consists of a filter capacitor C1, connected across the
rectifier output, an inductor L, in series and another filter capacitor connected across the
load.
1. The capacitor C1 offers low reactance to the AC component of the rectifier output
while it offers infinite reactance to the DC component. As a result the capacitor
shunts an appreciable amount of the AC component while the DC component
continues its journey to the inductor L
2. The inductor L offers high reactance to the AC component but it offers almost
zero reactance to the DC component. As a result the DC component flows through
the inductor while the AC component is blocked.
3. The capacitor C2 bypasses the AC component which the inductor had failed to
block. As a result only the DC component appears across the load RL.
Figure: Centered Tapped Full-Wave Rectifier with a Capacitor Filter
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Voltage Regulator
A voltage regulator is an electrical regulator designed to automatically maintain a
constant voltage level. It may use an electromechanical mechanism, or passive or active
electronic components. Depending on the design, it may be used to regulate one or more
AC or DC voltages. There are two types of regulator are they.
 Positive Voltage Series (78xx) and
 Negative Voltage Series (79xx)
78xx:
’78’ indicate the positive series and ‘xx’indicates the voltage rating. Suppose 7805
produces the maximum 5V.’05’indicates the regulator output is 5V.
79xx:
’78’ indicate the negative series and ‘xx’indicates the voltage rating. Suppose 7905
produces the maximum -5V.’05’indicates the regulator output is -5V.
These regulators consists the three pins there are
Pin1: It is used for input pin.
Pin2: This is ground pin for regulator
Pin3: It is used for output pin. Through this pin we get the output.
Figure: Regulator
Wireless Music transmission and reception by IR communication
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MELODY GENERATOR (UM66)
Wireless Music transmission and reception by IR communication
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UM66T is a melody integrated circuit. It is designed for use in bells, telephones, toys etc. It has an inbuilt
tone and a beat generator. The tone generator is a programmed divider which produces certain frequencies.
These frequencies are a factor of the oscillator frequency. The beat generator is also a programmed divider
which contains 15 available beats. Four beats of these can be selected.
There is an inbuilt oscillator circuit that serves as a time base for beat and tone generator. It has a 62 notes
ROM to play music. A set of 4 bits controls the scale code while 2 bits control the rhythm code. When
power is turned on, the melody generator is reset and melody begins from the first note. The speaker can be
driven by an external npn transistor connected to the output of UM66.
Many versions of UM66T are available which generate tone of different songs. For example, UM66T01
generates tone for songs ‘Jingle bells’, ‘Santa Claus is coming to town’ and ‘We wish you a merry X’mas’.
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Pin Description:
Pin No
1
2
3
Function
Name
Melody output
Supply voltage (1.5V - 4.5V)
Ground (0V)
Output
Vcc
Ground
FEATURES
*64-Note Rom memory
*1.5V~4,5V power supply and low power consumption
*Dynamic speaker can be driven with external NPN transistor
*OSC resistor hold mode
*Power on reset: melody begins from the first note
*Built in level hold mode
Wireless Music transmission and reception by IR communication
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IR Transmitter, Receiver
Wireless Music transmission and reception by IR communication
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IR SECTION:
WHAT IS INFRARED?
Infrared is a energy radiation with a frequency below our eyes sensitivity, so we cannot
see
it
Even that we can not "see" sound frequencies, we know that it exist, we can listen them.
Even that we can not see or hear infrared, we can feel it at our skin temperature sensors.
When you approach your hand to fire or warm element, you will "feel" the heat, but you
can't see it. You can see the fire because it emits other types of radiation, visible to your
eyes, but it also emits lots of infrared that you can only feel in your skin.
INFRARED IN ELECTRONICS
Infra-Red is interesting, because it is easily generated and doesn't suffer electromagnetic
interference, so it is nicely used to communication and control, but it is not perfect, some
other light emissions could contains infrared as well, and that can interfere in this
communication. The sun is an example, since it emits a wide spectrum or radiation.
The adventure of using lots of infra-red in TV/VCR remote controls and other
applications, brought infra-red diodes (emitter and receivers) at very low cost at the
market.
From now on you should think as infrared as just a "red" light. This light can means
something to the receiver, the "on or off" radiation can transmit different meanings.Lots
of things can generate infrared, anything that radiate heat do it, including out body,
lamps, stove, oven, friction your hands together, even the hot water at the faucet.
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To allow a good communication using infra-red, and avoid those "fake" signals, it is
imperative to use a "key" that can tell the receiver what is the real data transmitted and
what is fake. As an analogy, looking eye naked to the night sky you can see hundreds of
stars, but you can spot easily a far away airplane just by its flashing strobe light. That
strobe light is the "key", the "coding" element that alerts us.
Similar to the airplane at the night sky, our TV room may have hundreds of tinny IR
sources, our body and the lamps around, even the hot cup of tea. A way to avoid all those
other sources, is generating a key, like the flashing airplane. So, remote controls use to
pulsate its infrared in a certain frequency. The IR receiver module at the TV, VCR or
stereo "tunes" to this certain frequency and ignores all other IR received. The best
frequency for the job is between 30 and 60 KHz, the most used is around 36 KHz
IR GENERATION
To generate a 36 KHz pulsating infrared is quite easy, more difficult is to receive and
identify this frequency. This is why some companies produce infrared receives, that
contains the filters, decoding circuits and the output shaper, that delivers a square wave,
meaning the existence or not of the 36kHz incoming pulsating infrared.
It means that those 3 dollars small units, have an output pin that goes high (+5V)
when there is a pulsating 36kHz infrared in front of it, and zero volts when there is not
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this radiation.
A square wave of approximately 27uS (microseconds) injected at the base of a transistor,
can drive an infrared LED to transmit this pulsating light wave. Upon its presence, the
commercial receiver will switch its output to high level (+5V).If you can turn on and off
this frequency at the transmitter, your receiver's output will indicate when the transmitter
is on or off.
Those IR demodulators have inverted logic at its output, when a burst of IR is sensed it
drives its output to low level, meaning logic level = 1.
The TV, VCR, and Audio equipment manufacturers for long use infra-red at their remote
controls. To avoid a Philips remote control to change channels in a Panasonic TV, they
use different codification at the infrared, even that all of them use basically the same
transmitted frequency, from 36 to 50 KHz. So, all of them use a different combination of
bits or how to code the transmitted data to avoid interference.
RC-5
Various remote control systems are used in electronic equipment today. The RC5
control protocol is one of the most popular and is widely used to control numerous home
appliances, entertainment systems and some industrial applications including utility
consumption remote meter reading, contact-less apparatus control, telemetry data
transmission, and car security systems. Philips originally invented this protocol and
virtually all Philips’ remotes use this protocol. Following is a description of the RC5.
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When the user pushes a button on the hand-held remote, the device is activated and sends
modulated infrared light to transmit the command. The remote separates command data
into packets. Each data packet consists of a 14-bit data word, which is repeated if the user
continues to push the remote button. The data packet structure is as follows:

2 start bits,

1 control bit,

5 address bits,

6 command bits.
The start bits are always logic ‘1’ and intended to calibrate the optical receiver automatic
gain control loop. Next, is the control bit. This bit is inverted each time the user releases
the remote button and is intended to differentiate situations when the user continues to
hold the same button or presses it again. The next 5 bits are the address bits and select the
destination device. A number of devices can use RC5 at the same time. To exclude
possible interference, each must use a different address. The 6 command bits describe the
actual command. As a result, a RC5 transmitter can send the 2048 unique commands.
The transmitter shifts the data word, applies Manchester encoding and passes the created
one-bit sequence to a control carrier frequency signal amplitude modulator. The
amplitude modulated carrier signal is sent to the optical transmitter, which radiates the
infrared light. In RC5 systems the carrier frequency has been set to 36 kHz. Figure below
displays the RC5 protocol.
The receiver performs the reverse function. The photo detector converts optical
transmission into electric signals, filters it and executes amplitude demodulation. The
receiver output bit stream can be used to decode the RC5 data word. This operation is
done by the microprocessor typically, but complete hardware implementations are
present on the market as well. Single-die optical receivers are being mass produced by a
number of companies such as Siemens, Temic, Sharp, Xiamen Hualian, Japanese Electric
and others. Please note that the receiver output is inverted (log. 1 corresponds to
illumination absence).
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IR TRANSMITTER:
The IR LED emitting infrared light is put on in the transmitting unit. To generate
IR signal, 555 IC based astable multivibrator is used. Infrared LED is driven through
transistor BC 548.
IC 555 is used to construct an astable multivibrator which has two quasi-stable
states. It generates a square wave of frequency 38 kHz and amplitude 5Volts. It is
required to switch ‘ON’ the IR LED. The IR transmitter circuit is as shown below:
555 TIMER:
The 555 is an integrated circuit (chip) implementing a variety of timer and
multivibrator applications. It was designed in 1970 and introduced in 1971 by Signetics
(later acquired by Philips). The original name was the SE555/NE555 and was called
"The IC Time Machine". It is still in wide use, thanks to its ease of use, low price and
good stability. As of 2003, 1 billion units are manufactured every year.
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The 555 timer is one of the most popular and versatile integrated circuits ever
produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in
an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that combines two
555s on a single chip.
Fig: 555 timer
Pin Functions - 8 pin package
Ground (Pin 1)
This pin is connected directly to ground.
Trigger (Pin 2)
This pin is the input to the lower comparator and is used to set the latch, which in turn
causes the output to go high.
Output (Pin 3)
Output high is about 1.7V less than supply. Output high is capable of sourcing up to
200mA while output low is capable of sinking up to 200mA.
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Reset (Pin 4)
This is used to reset the latch and return the output to a low state. The reset is an
overriding function. When not used connect to V+.
Control (Pin 5)
Allows access to the 2/3V+ voltage divider point when the 555 timer is used in voltage
control mode. When not used connect to ground through a 0.01 uF capacitor.
Threshold (Pin 6)
This is an input to the upper comparator.
Discharge (Pin 7)
This is the open collector to Q14.
V+ (Pin 8)
This connects to Vcc and the Philips data book states the ICM7555 CMOS version
operates 3V - 16V DC while the NE555 version is 3V - 16V DC.
The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applications
include timers, missing pulse detection, bounce free switches, touch switches,
Frequency Divider, Capacitance Measurement, Pulse Width Modulation (PWM)
etc

Astable mode: Free Running mode: the 555 can operate as an oscillator. Uses
include LED and lamp flashers, pulse generation, logic clocks, tone generation,
security alarms, pulse position modulation, etc.

Bistable mode: The 555 can operate as a flip-flop, if the DIS pin is not connected
and no capacitor is used. Uses include bounce free latched switches, etc.
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How to generate frequency with astable multi based on 555 timer?
This circuit diagram shows how a 555 timer IC is configured to function as an
astable multivibrator. An astable multivibrator is a timing circuit whose 'low' and
'high' states are both unstable. As such, the output of an astable multivibrator toggles
between 'low' and 'high' continuously, in effect generating a train of pulses. This
circuit is therefore also known as a 'pulse generator' circuit.
In this circuit, capacitor C1 charges through R1 and R2, eventually building up
enough voltage to trigger an internal comparator to toggle the output flip-flop. Once
toggled, the flip-flop discharges C1 through R2 into pin 7, which is the discharge pin.
When C1's voltage becomes low enough, another internal comparator is triggered to
toggle the output flip-flop. This once again allows C1 to charge up through R1 and R2
and the cycle starts all over again.
C1's charge-up time t1 is given by: t1 = 0.693(R1+R2) C1. C1's discharge time
t2 is given by: t2 = 0.693(R2) C1. Thus, the total period of one cycle is t1+t2 = 0.693
C1 (R1+2R2). The frequency f of the output wave is the reciprocal of this period, and
is therefore given by:
f = 1.44/ (C1 (R1+2R2))
where f is in Hz if R1 and R2 are in megaohms and C1 is in microfarads.
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IR RECEIVER
Description
The TSOP17.. – Series are miniaturized receivers for infrared remote control
systems. PIN diode and preamplifier are assembled on lead frame, the epoxy package is
designed as IR filter.
The demodulated output signal can directly be decoded by a microprocessor.
TSOP17.. is the standard IR remote control receiver series, supporting all major
transmission codes.
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Features

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance

TTL and CMOS compatibility

Output active low

Low power consumption

High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Suitable burst length .10 cycles/burst

Suitable Data Format
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The circuit of the TSOP17 is designed in that way that unexpected output pulses
due to noise or disturbance signals are avoided. A bandpass filter, an integrator stage and
an automatic gain control are used to suppress such disturbances. The distinguishing
mark between data signal and disturbance signal are carrier frequency, burst length and
duty cycle. The data signal should fulfil the following condition:
• Carrier frequency should be close to center frequency of the bandpass (e.g. 38 KHz).
• Burst length should be 10 cycles/burst or longer.
• After each burst which is between 10 cycles and 70 cycles a gap time of at least 14
cycles is necessary.
• For each burst which is longer than 1.8ms a corresponding gap time is necessary at
some time in the data stream. This gap time should have at least same length as the burst.
• Up to 1400 short bursts per second can be received continuously.
Some examples for suitable data format are: NEC Code, Toshiba Micom Format,
Sharp Code, RC5 Code, RC6 Code, R–2000 Code and Sony Format (SIRCS). When a
disturbance signal is applied to the TSOP17.. It can still receive the data signal. However
the sensitivity is reduced to that level that no unexpected pulses will occur. Some
examples for such disturbance signals which are suppressed by the TSOP17 are:
• DC light (e.g. from tungsten bulb or sunlight)
• Continuous signal at 38 kHz or at any other frequency
• Signals from fluorescent lamps with electronic ballast (an example of the signal
modulation is in the figure below).
IR Emitter and IR phototransistor:
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An infrared emitter is an LED made from gallium arsenide, which emits nearinfrared energy at about 880nm. The infrared phototransistor acts as a transistor with the
base voltage determined by the amount of light hitting the transistor. Hence it acts as a
variable current source. Greater amount of IR light cause greater currents to flow through
the collector-emitter leads. As shown in the diagram below, the phototransistor is wired
in a similar configuration to the voltage divider.
The variable current traveling through the resistor causes a voltage drop in the pull-up
resistor. This voltage is measured as the output of the device
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Photo
IR reflectance sensors contain a matched infrared transmitter and infrared receiver pair.
These devices work by measuring the amount of light that is reflected into the receiver.
Because the receiver also responds to ambient light, the device works best when well
shielded from abient light, and when the distance between the sensor and the reflective
surface is small(less than 5mm).
IR reflectance sensors are often used to detect white and black surfaces. White surfaces
generally reflect well, while black surfaces reflect poorly. One of such applications is the
line follower of a robot.
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Schematic Diagram for a Single Pair of Infrared Transmitter and Receiver
Theory of
Sensor
Circuit
To get a
good
voltage
swing , the
value
of
must
carefully
be
R1
chosen. If Rsensor = a when no light falls on it and Rsensor = b when light falls on it.
The difference in the two potentials is:
Vcc * { a/(a+R1) - b/(b+R1) }
Relative voltage swing = Actual Voltage Swing / Vcc
= Vcc * { a/(a+R1) - b/(b+R1) } / Vcc
= a/(a+R1) - b/(b+R1)
The resistance of the sensor decreases when IR light falls on it. A good sensor will have
near zero resistance in presence of light and a very large resistance in absence of light.
We have used this property of the sensor to form a potential divider. The potential at
point ‘2’ is Rsensor / (Rsensor + R1). Again, a good sensor circuit should give maximum
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change in potential at point ‘2’ for no-light and bright-light conditions. This is especially
important if you plan to use an ADC in place of the comparator
To get a good voltage swing , the value of R1 must be carefully chosen. If Rsensor = a
when no light falls on it and Rsensor = b when light falls on it. The difference in the two
potentials is:
Vcc * { a/(a+R1) - b/(b+R1) }
Relative voltage swing = Actual Voltage Swing / Vcc
= Vcc * { a/(a+R1) - b/(b+R1) } / Vcc
= a/(a+R1) - b/(b+R1)
If
the emitter and detector (aka phototransistor) are not blocked, then the output on pin 2 of
the 74LS14 will be high (apx. 5 Volts). When they are blocked, then the output will be
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low (apx. 0 Volts). The 74LS14 is a Schmitt triggered hex inverter. A Schmitt trigger is a
signal conditioner. It ensures that above a threshold value, we will always get "clean"
HIGH and LOW signals. Not Blocked Case: Pin 2 High Current from Vcc flows through
the detector. The current continues to flow through the base of Q2. Current from Vcc also
flows through R2, and Q2's Drain and Emitter to ground. As a result of this current path,
there will be no current flowing through Q1's base. The signal at U1's pin 1 will be low,
and so pin 2 will be high. Blocked Case: Pin 2 Low Current "stops" at the detector.
Q2's base is not turned on. The current is re-routed passing through R2 and into the base
of Q1. This allows current to flow from Q1's detector and exiting out Q1's emitter. Pin 1
is thus high and pin 2 will be low. To detect a line to be followed, we are using two or
more number of photo-reflectors. Its output current that proportional to reflection rate of
the floor is converted to voltage with a resister and tested it if the line is detected or not.
However the threshold voltage cannot be fixed to any level because optical current by
ambient light is added to the output current.
Most photo-detecting modules are using moderated light to avoid interference by the
ambient light. The detected signal is filtered with a band pass filter and disused signals
are filtered out. Therefore only the moderated signal from the light emitter can be
detected.
Of course the detector must not be saturated by ambient light, this is effective when the
detector is working in linear region.
The
line
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position is compared to the center value to be tracked, the position error is processed with
Proportional/Integral/Diffence filters to generate steering command. The line following
robot tracks the line in PID control that the most popular algorithm for servo control.
The proportional term is the common process in the servo system. It is only a gain
amplifier without time dependent process.
The differential term is applied in order to improve the response to disturbance, and it
also compensate phase lag at the controlled object.
The D term will be required in most case to stabilize tracking motion. The I term that
boosts DC gain is applied in order to remove left offset error, however, it often decrease
servo stability due to its phase lag.
When any line sensing error has occurred for a time due to getting out of line or end of
line, the motors are stopped and the microcontroller enters sleep state of zero power
consumption.
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TRANSISTOR DRIVER CIRCUIT:
An SPDT relay consists of five pins, two for the magnetic coil, one as the common
terminal and the last pins as normally connected pin and normally closed pin. When the
current flows through this coil, the coil gets energized. Initially when the coil is not
energized, there will be a connection between the common terminal and normally closed
pin. But when the coil is energized, this connection breaks and a new connection between
the common terminal and normally open pin will be established. Thus when there is an
input from the microcontroller to the relay, the relay will be switched on. Thus when the
relay is on, it can drive the loads connected between the common terminal and normally
open pin. Therefore, the relay takes 5V from the microcontroller and drives the loads
which consume high currents. Thus the relay acts as an isolation device.
Digital systems and microcontroller pins lack sufficient current to drive the circuits like
relays and buzzer which consume high powers. While the relay’s coil needs around
10milli amps to be energized, the microcontroller’s pin can provide a maximum of 12milli amps current. For this reason, a driver such as a power transistor is placed in
between the microcontroller and the relay.
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Vcc
RELAY
GROUND
The operation of this circuit is as follows:
The input to the base of the transistor is applied .The transistor will be switched on when
the base to emitter voltage is greater than 0.7V (cut-in voltage). Thus when the voltage
applied to the (>0.7V), the transistor will be switched on and thus the relay will be ON
and the load will be operated.
When the voltage at (<0.7V) the transistor will be in off state and the relay will be OFF.
Thus the transistor acts like a current driver to operate the relay accordingly.
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Buzzer
A buzzer or beeper is an audio signaling device, which may be mechanical,
electromechanical, or electronic. Typical uses of buzzers and beepers include alarms,
timers and confirmation of user input such as a mouse click or keystroke. Early devices
were based on an electromechanical system identical to an electric bell without the metal
gong. Similarly, a relay may be connected to interrupt its own actuating current, causing
the contacts to buzz. Often these units were anchored to a wall or ceiling to use it as a
sounding board. The word "buzzer" comes from the rasping noise that electromechanical
buzzers made.
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60db siren
A siren is a loud noise maker. Most modern ones are civil defense or air- raid sirens,
tornado sirens, or the sirens on emergency service vehicles such as ambulances, police
cars and fire trucks. There are two general types, pneumatic and electronic.
Many fire sirens serve double duty as tornado or civil defense sirens, alerting an
entire community of impending danger. Most fire sirens are either mounted on the roof of
a fire station, or on a pole next to the fire station. Fire sirens can also be mounted near
government buildings, on top of tall structures such as water towers, as well as in
systems, where several sirens are distributed around a town for better sound coverage.
Most fire sirens are single tone and mechanically driven by electric motors with a rotor
attached to the shaft.
Some newer sirens are electronically driven by speakers, though these are not as
common. Fire sirens are often called "fire whistles", "fire alarms", "fire horns." Although
there is no standard signaling of fire sirens, some utilize codes to inform firefighters to
the location of the fire. Civil defense sirens pulling double duty as a fire siren often can
produce an alternating "hi-lo" signal (similar to a British police car) as the fire signal, or a
slow wail (typically 3x) as to not confuse the public with the standard civil defense
signals of alert (steady tone) and attack (fast wavering tone).
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Electronic sirens incorporate circuits such as oscillators, modulators, and
amplifiers to synthesize a selected siren tone (wail, yelp, pierce/priority/phaser, hi-lo,
scan, airhorn, manual, and a few more) which is played through external speakers. It is
not unusual, especially in the case of modern fire engines, to see an emergency vehicle
equipped with both types of sirens. Often, police sirens also use the interval of a tritone to
help draw attention.
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Advantages:
Highly sensitive
Two stage Gain control
Very low noise
Low cost and reliable circuit
Can transmit up to 10 meter
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Applications:
Wireless Speaker System
Welcome Tone generators at entrance
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Conclusion
The project “Wireless Music transmission and reception by IR communication
” is designed, tested and implemented successfully. It is much easy and cost effective.
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REFERENCES:
Text Books:
Website:
www.howstuffworks.com
www.answers.com
www.WineYard.in
Magazines:
Electronics for you
Electrikindia
Go Wireless
Wireless Music transmission and reception by IR communication