Download uC based Whether Activated Car System

Anti-collision and Anti-braking Intelligent CAR
We live in a world where everything can be controlled and
operated automatically, but there are still a few important sectors in
our country where automation has not been adopted or not been
put to a full-fledged use, perhaps because of several reasons one
such reason is cost. Intelligent car form an important part of the
automobile sectors in our country as they can be used to grow
production of such automated feature in car at low cost . Automating
a CAR envisages monitoring and controlling of the climatic
parameters which directly or indirectly govern saving of battery
an can avoid accident condition.
PWM Technique used for Anti-Braking and Anti-collision
Pulse Width Modulation (PWM) is a commonly used technique for
generally controlling DC power to an electrical device, made practical by modern
electronic power switches. However it also finds its place in AC choppers. The
average value of current supplied to the load is controlled by the switch position
and duration of its state. If the On period of the switch is longer compared to its
off period, the load receives comparatively higher power. Thus the PWM
switching frequency has to be faster.
Typically switching has to be done several times a minute in an electric
stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a
motor drive.
Switching frequency for audio amplifiers and computer power supplies is
about ten to hundreds of kHz. The ratio of the On time to the time period of the
pulse is known as duty cycle. If the duty cycle is low, it implies low power.
The power loss in the switching device is very low, due to almost
negligible amount of current flowing in the Off state of the device and negligible
amount of voltage drop in its off state. Digital controls also use PWM technique.
PWM has also been used in certain communication systems where its
duty cycle has been used to convey information over a communications channel.
Power delivery
PWM can be used to adjust the total amount of power delivered to a load
without losses normally incurred when a power transfer is limited by resistive
means. The drawbacks are the pulsations defined by the duty cycle, switching
frequency and properties of the load. With a sufficiently high switching
frequency and, when necessary, using additional passive electronic filters the
pulse train can be smoothed and average analogue waveform recovered. High
frequency
PWM
control
systems
can
be
easily
implemented
using
semiconductor switches.
As has been already stated above almost no power is dissipated by the switch in
either on or off state. However, during the transitions between on and off states
both voltage and current are non-zero and thus considerable power is dissipated
in the switches. Luckily, the change of state between fully on and fully off is
quite rapid (typically less than 100 nanoseconds) relative to typical on or off
times, and so the average power dissipation is quite low compared to the power
being delivered even when high switching frequencies are used.
TRANSDUCERS
A transducer is a device which measures a physical quantity and
converts it into a signal which can be read by an observer or by
an instrument. Monitoring and controlling of a CARs environment
involves sensing the changes occurring inside it which can influence
the rate of growth in plants. The parameters which are of importance
are the temperature
inside
the CAR also touch, water, the
illumination etc. Since all these parameters are interlinked, a closed
loop (feedback) control system is employed in monitoring it. The
sensors used in this system are:
1. Water Sensor(Transistor amplifier)
2. Light Sensor ( LDR (Light Dependent Resistor) )
3. Temperature Sensor
4.Touch Sensor.
Water SENSOR
Features of the Water sensor:
1.The circuit designed uses a 5V supply, fixed resistance of 100Ω,
variable resistance of 10ΚΩ, two copper leads as the sensor probes,
2N222N/BC548 transistor
2.It gives a voltage output corresponding to the conductivity of the
two point on CAR if raining.
3.The conductivity depends upon the amount of water present on
the CAR .
4.The voltage output is taken at the transmitter which is connected
to a variable resistance. This variable resistance is used to adjust the
sensitivity of the sensor.
Fig.Soil
Moisture
Sensor
Functional description of Soil moisture sensor:
The two copper leads act as the sensor probes. They are connected on
the Front and Rear glass of the CAR whose water content is under
test.
Case#1: Dry condition- The probes are placed dry conditions on the
glass. As there is no conduction path between the two copper leads
the sensor circuit remains open. The voltage output of the emitter in
this case ranges from 0 to 0.5V.
Case#2: Excess water
condition-
With the increase in water
content beyond the level, the conductivity increases drastically and
a steady conduction path is established between the two sensor leads
and the voltage output from the sensor increases no further beyond
a certain limit. The maximum possible value for it is not more than
4.2V to 5.0V.
LIGHT SENSOR
Light Dependent Resistor (LDR) also known as photoconductor or
photocell, is a device which has a resistance which varies according
to the amount of light falling on its surface. Since LDR is extremely
sensitive in visible light range, it is well suited for the proposed
application.
Fig. 3.2 Light Dependent Resistor
Features of the light sensor:
The Light Dependent Resistor (LDR) is made using
the semiconductor Cadmium Sulphide (CdS).
The light falling on the brown zigzag lines on the sensor causes the
resistance of the device to fall. This is known as a negative coefficient. There are some LDRs that work in the opposite way i.e.
their resistance increases with light (called positive coefficient).
The resistance of the LDR decreases as the intensity of the light
falling on it increases. Incident photons drive electrons from the
valence band into the Conduction Band
Light Dependent Resistor
Fig. Structure of a Light Dependent Resistor, showing Cadmium
Sulphide track and an atom to illustrate electrons in the valence
and conduction bands
An LDR and a normal resistor are wired in series across a voltage, as
shown in the circuit below. Depending on which is tied to the 5V and
which to 0V, the voltage at the point between them, call it the
sensor node, will either rise or fall with increasing light. If the LDR
is the component tied directly to the 5V, the sensor node will
increase in voltage with increasing light
The LDR's resistance can reach 10 k ohms in dark conditions and
about 100 ohms in full brightness.
Fig.Light Sensor
The circuit used for sensing light in our system uses a 10 kΩ fixed
resistor which istied to +5V. Hence the voltage value in this case
decreases with increase in light intensity levels of light intensity
corresponding to the four conditions- Optimum, dim, dark and night.
TEMPERATURE SENSOR
National Semiconductor s LM35 IC has been used for sensing the
temperature It is an integrated circuit sensor that can be used to
measure temperature with an 0electrical output proportional to
the temperature (in oC). The temperature can be measured more
accurately with it than using a thermistor. The sensor circuitry is
sealed and not subject to oxidation, etc.
The sensor node voltage is compared with the threshold voltages
for different
Fig.Temperature Sensor LM35
Features:
• Calibrated directly in ° Celsius (Centigrade)
• Linear + 10.0 mV/°C scale factor
• 0.5°C accuracy guaranteed (at +25°C)
• Rated for full −55° to +150°C range
• Suitable for remote applications
• Low cost due to wafer-level trimming
• Operates from 4 to 30 volts
• Less than 60 μA current drain
• Low self-heating, 0.08°C in still air
• Nonlinearity only ±1⁄4°C typical
Functional description:
• The sensor has a sensitivity of 10mV / ˚C.
• The output of LM35 is amplified using a LM324 single power
supply (+5V) op-amp.
• The op-amp is designed to have a gain of 5.
• The circuitry measures temperatures with a resolution of up to 0.5
degree Celsius.
• The output voltage is converted to temperature by a simple
conversion factor. The
general equation used to convert output voltage to temperature is:
Temperature (˚C) = (Vout * 100 ) / 5 ˚C
So if Vout is 5V, then, Temperature = 100 ˚C
• The output voltage varies linearly with temperature.
Touch Sensor
Touch Sensing Circuit
This kit combines a Touch Switch and a Touch Plate all
together in the same . In the Touch Switch two leads must be shorted
together by your finger touching them. In the Touch Plate only one
plate needs to be touched. The Touch Switch only needs a battery to
activate It but the Touch Plate requires a mains power supply.
A Relay rated at 240V Is Included with the kit o that you
may use to switch a light r other mains appliance. To use the relay
you must use a 12V supply taken from a mains power supply.
Note:
The use of the Relay to switch 220V supply with this project
MUST use the correct boxes and connectors to protect you and
anyone else who uses the kit.
The kit is constructed on a single- sided printed circuit board (PCB).
A computer aided design program is used to design the board.
Circuit Description
The main part of the circuit is the two NAND gates of the
4011 IC which are connected as a flip-flop. Pins 9 and 13 are the ON
and OFF contacts. The two gates are connected to the positive rail by
the two 1OM resistors. Shorting one of the gates with the ground rail
by touching it (this is equivalent to connecting about 50K between the
gate and ground) FLIPs the output to that state. Shorting out the
other contact FLOPs it back again. The output of the flip-flop drives a
transistor connected as a switch. it switches an LED and a relay. The
relay Is rated to switch 24W. Connecting the two 1K resistors
connects the other two NAND gates of the IC Into the flip-flop and
makes it much more sensitive to touch. The touch plate may in fact
work with only the first two gates connected. But, it will be much
more sensitive with all four gates connected as a flip-flop.
The Touch Switch waits by capacitive pickup of the mains
hum. When the contact Is touched body capacitance picking up
general RF in the air is enough to short the plate to ground. Because
the touch plate uses mains hum as it method of shorting the gate to
ground a mains connected power supply must be used to supply
power to the switch. A battery will not work. The 4011 is a quad (4,2)
Input, NAND gate. The data sheet is included with this
documentation.
Obstacle Detector
This circuit has two stages: a transmitter unit and a receiver unit. The transmitter
unit consists of an infrared LED and its associated circuitry.
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 38kHz and amplitude 5Volts.
It is required to switch ‘ON’ the IR LED.
IR RECEIVER:
The receiver unit consists of a sensor and its associated circuitry. In receiver
section, the first part is a sensor, which detects IR pulses transmitted by IR-LED.
Whenever a train crosses the sensor, the output of IR sensor momentarily transits through
a low state. As a result the monostable is triggered and a short pulse is applied to the port
pin of the 8051 microcontroller. On receiving a pulse from the sensor circuit, the
controller activates the circuitry required for closing and opening of the gates and for
track switching. The IR receiver circuit is shown in the figure below.
Circuit Diagram