CHAPTER III
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CIRCUIT DIAGRAM AND DESCRIPTION
3.1
TRANSMITTER
AND
RECEIVER
FOR
LAND
ROVER
3.1.1TRANSMITTER
The radio frequency transmitter (SCTX2B) is used as multiplexer which
sends corresponding switching pulse to signal processor unit. Signal
processing unit has large signal amplifier (complementary symmetry
amplifier) and crystal oscillator for frequency signal generation and
transmission.
The frequencies used are 35.005MHz, 35.015MHz, 35.025MHz, and
35.035MHz for Forward, Reverse and Left and Right motion respectively.
3.1.2RECEIVER
The receiver has radio frequency receiver (SCRX2FS), it also has in built
signal processing unit which process the serial data received and gives to
the motor switching unit. This switching unit has negative feedback
differential amplifier which switches corresponding motor in specified
direction according to received signal.
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3.2 TRANSMITTER AND RECEIVER FOR ARM
3.2.1 TRANSMITTER
The transmitter circuit has parallel to serial data multiplexer (HT12E) and
RF transmitter TX02. It also has 6 push button and 8 diodes. When a push
button is pressed corresponding parallel input is given to multiplexer and
serial data output from multiplexer is given to transmitter which transmits
corresponding radio frequency signal (35MHz).
3.2.2 RECEIVER
The receiver circuit has serial to parallel data De-multiplexer (HT12D),
Micro- controller (89C51) and RF receiver RX02. It also has 6 switching
transistors and 6 relays. When a signal is received RX02 will give the
serial data signal to De-multiplexer (HT12D) which converts it into
parallel data. This parallel data will be given to Port1 pins of Microcontroller. The Micro-controller is pre -programmed based on requirement
of the operation. The outputs are taken from Port3 pins of Microcontroller. These binary outputs are given to corresponding switching
transistors. This activates corresponding relay and hence drives the
specified motor in required direction.
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3.3 AUTOMATIC LIGHT ILLUMINATION
In Automatic illumination system the LDR acts as sensor which
activates/deactivates the relay (connected to doom light) depending on
light illumination of environment.
At low light illumination environment, resistance of LDR becomes high of
mega-Ohms and activates the relay to switch on doom light array. At light
illumination environment resistance of LDR drops and deactivates the
relay. The Relay used here is 6V, 1A coil and operating principle is of
electromagnetic type. Connections of doom light can be brought out of
PCB and can be placed anywhere in robot. White LED array with polished
reflectors surrounding the LED array has good illumination.
3.4 TEMPERATURE SENSOR
A reverse biased germanium diode is used here as a temperature sensor. At
room temperature the reverse resistance of the diode being very high (over
10K Ω), it produces no effect on transistor T1 which conducts and keeps
the reset pin (4) of IC1 at ‘ground level’ and so the alarm does not sound.
When temperature in the vicinity of diode D1 (the sensor) increases in case
of a high temperature, the reverse resistance of D1 drops.
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At about 40 degree Celsius its resistance drops to a value below 1KΩ.
This stops T1’s conduction and the IC’s reset pin 4 becomes positive
through resistance R2, which sounds the alarm.
3.5 HIGH SENSITIVE METAL DETECTOR
The circuit in High sensitive Metal detector works on the principle of
detecting the amplitude of a waveform. This is called Amplitude
Modulation.
When a metal object is placed near the detecting coil, some of the magnetic
flux passes into the object and creates a current called eddy-current. This
uses-up some of the magnetic flux and thus less flux is available for the
receiving secondary coil.
This produces a lower output from the coil and causes the second transistor
in the circuit to be turned OFF slightly and the voltage on the collector
rises. This allows the third and fourth transistors to oscillate and pass a
signal to the fifth transistor to drive a mini speaker.
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