ABSTRACT
Wireless
speaker is a type of speaker that transmits audio signals using radio frequency
(RF) waves rather than over audio cables. As things stands today, the term
‘wireless’ in the audio and video world does not mean wireless rather all it
means is less wires. A common complaint against home audio systems has been the
cables that interconnect the speakers to the audio receiver, tuner, CD player,
or stereo units. As more and more channels are added to modern audio equipment,
the problem of connecting the speakers to the audio sources is getting worst.
In
this project, a wireless loudspeaker which will transmit using radio frequency
(RF) is designed and constructed. The receiver and the transmitter circuits
were implemented to achieve the aim of this project.
The
method used involves the design of the receiver and the transmitter circuits as
well as the amplifier and the nature of the mixer. The transmitter was designed
to use a 9V battery which can easily be replaced. The radius of reception is
within 100meters with a power output of 0.03MW. The amplifier was designed to
produce an output power of 20W to an 8ohms (8
) loudspeaker.The audio amplifier was
powered from the rectified 220Vac.supply.The receiver consists of an aerial and
a demodulator with the help of a tuned circuit which helps to pick the required
signal.
The
components were initially mounted on breadboard and tested; some of the
mistakes were corrected before finally transferring it onto the printed circuit
board (PCB) for permanent soldering. The whole circuit was
successfully tested, and it was observed that the system is functioning in
optimal condition. Due to this fact, one can rate the project’s performance at
about 87%.
The
constructed wireless loudspeaker system can stand the test of time in its
performance. It is very reliable, and the overall performance is excellent. Conclusively
the wireless loudspeaker system successfully achieved the aim of transmitting
and receiving voice signals over a distance. I learnt and researched more on
the use of modulation and demodulation, the amplifier circuitry etc.
CHAPTER
ONE
INTRODUCTION
1.1 PREAMBLES
Wireless
speakers are very similar to traditional loudspeakers that are wired, but they transmit
audio signals using radio frequency (RF) waves rather than over audio cables.
As things stands today, the term 'wireless' in the audio and video world does
not mean 'wireless' - rather all it means is less wires. And this applies to
any wireless speaker system presently. Still, this in itself can turn out to be
a great advantage. Home audio systems can be enhanced and made more versatile
by incorporating the ability to listen to music from a single source in
multiple locations. However, distributing music throughout the homes, theaters,
churches, stadiums, arenas, and broadcast facilities has proved to be
logistically difficult (Syafiqah, 2010). Home owners could extend the listening
range of an audio source by purchasing a multi-room amplifier and having
additional wiring installed through-out the house by a professional
electrician. However, for many consumers who do not own their homes or who
cannot afford such an upgrade, this solution would be impractical. The
alternative of having interconnecting wires laid out visibly throughout the
home has also been unappealing to most consumers for reasons of safety and
aesthetics. Therefore, the lack of an available, affordable technology that
would overcome the need for wired audio device interconnection greatly
restricted the home audio possibilities for most people. Recently, wireless
systems have become available that offer home wide music distribution that is
in many cases more practical and more elegant than the wired methods previously
mentioned Using wireless communication technology for home entertainment
becomes popular.
Wireless
speaker system is not a new invention for this century; however, the goal of
this project is to improve the size, quality and range of the communication
system. Here, wireless speakers are composed of two units: a main speaker unit
combining the loudspeaker itself with an RF receiver, and an RF transmitter
unit (Syafiqah, 2010). There is normally an amplifier integrated in the
speaker's cabinet because the RF waves alone are not enough to drive the
speaker. This integration of amplifier and loudspeaker is known as an active
loudspeaker. Manufacturers of these loudspeakers design them to be as
lightweight as possible while producing the maximum amount of audio output efficiency.
Wireless speakers still need power, so require a nearby AC power outlet, or
possibly batteries (DC). Only the wire to the amplifier is eliminated.
The
transmitter connects to the audio output of audio devices like speakers.
Wireless technology is relatively new for home surround sound systems as well
as other systems. There are two types of transmission media for wireless
speakers. RF signal based systems, and infrared signal based systems. RF, or
radio frequency based systems use radio signals to transmit data, and in this
case music, to the remote receiver. RF systems commonly use radio frequencies
between 300 MHz and 1000 MHz, with 900 MHz being the most common frequency.
Transaction rates range up to 40,000 bits per second (Binti, 2011).
This technology does well for speaker systems
that will not have direct LOS (line of sight) from the receiver to the
transmitter. Some barriers, such as cement, metal, electronic devices, some
plastics, and other materials interrupt or absorb RF signals. The speaker
placement can be test by moving speakers around slightly to see where the best
reception and audio quality is. This solution is common for outdoor speaker systems,
systems that are located in a different room that the audio source, or home
wide audio systems. In the location where it would like to place, the speakers
is limited to areas of bad coverage, RF repeaters can be purchased to assist
transmissions around barriers that are causing transmission problems (Syafiqah,
2010).
These
systems are susceptible to radio interference from electronic devices, although
new technologies in shielding and spread spectrum solutions are making this
less of an issue. RF systems tend to transmit more data, communicate further,
are more reliable and are more expensive than the infrared alternative. A
transmitter in a wireless network is responsible for generating a high power
output signal with adequate signal strength to deliver a sender's message.
Wireless transmitters provide modulated radio waves to carry (transmit) data
signals from one place to another that may include a radio frequency (RF)
filter system which is used to ensure that the integrity of a sender's message
is not threatened by the many compromising system components that the signal
encounters as it progresses through the transmitter.