CHAPTER ONE
INTRODUCTION
The vehicle system control
using telemetry application is all about using a radio wave to control and
activate certain events such as the car horn, car head light, car ignition
(starter) and car air conditioner etc.
This is achieved by using various tone frequencies by using
an encoder via a radio frequency transmitter (low power) that provides the
carrier frequency for these tones.
At the receiver end demultiplexing and decoding of these
tone takes place via a detector/receiver stage. The output of the encoder is
used to turn on a relay switch, which inturn connects power source to either
the car engine, horn or lamp etc.
The application of thus project include space exploration,
where lunar vehicles are controlled from earth station by using satellite as
the medium of transfer of signals.
In the military warfare, unmanned air crafts, missiles and
even armoured tanks are controlled these days by using the pinaple of telemetry
applications. Other areas include GSM, where a subscriber has the total control
of his telephone calls conversation through the BTS (Base Transmission or
Transceiver Station). Its application are so vast and large that they are too
numerous to mention.
BLOCK DIAGRAM FOR
TRANSMITTER CONTROL UNIT
BLOCK DIAGRAM FOR RECEIVER CONTROL UNIT
Telemetry system has two units the
transmitter and receiver. The link between the two unit is radio wave. The
transmitter sends tones of different frequencies the receiver receives the
tones.
TRANSMITTER
Transmitter
is a device that process and possibly encode information, so as to make it
suitable for transmission and subsequent reception. In a transmitter the
information modulates the carrier. It superimposed an a light frequency since
wave modulation varies from one system to another and may be high or low
levels. Modulations is of three types amplitude modulation, frequency modulation
and pulse modulation or combination of these.
FREQUENCY
MODULATION:
Frequency
modulation is a system in which the amplitude of the modulated carrier is
constant while its frequency and rate of change are varied by the modulating
signal. Frequency modulation is much more immune to noise than amplitude
modulation noise vector is superimposed on the carrier.
RADIO WAVE
This is
simply passing information via electromagnetic wave. Radio communicating use
electromagnetic waves to carry information over long distances. These radio
waves usually propagate through the earth’s atmosphere to places where they
induces EMFs in the antennas of a distant receiver. The main modes of
propagation are grand wave propagation sky wave propagation and space wave
propagation.
TRANSMITTER
UNIT
INPUT
VARIABLE (KEY PAD) UNIT
The input variable unit is
designed using make and break switches. By toggling each switch, the input
signal to the encoder circuit becomes active low. Each of these switches
corresponds to different signal tones.
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