INTRODUCTION

Automobiles are synonyms for mobility and freedom.

An amazing increase in the growth of population in this world leads to the rapid

increase in the number of vehicle being used. With the growing number of

vehicles and the consequent shortage of parking space, there is haphazard and

totally unregulated parking of vehicles all over. In densely populated areas they

are real challenge for city planners, architects and developers. The need to offer

sufficient parking spaces is a task for specialists. This situation calls for the

need for an automated parking system that not only regulates parking in a given

area but also keeps the manual control to a minimum. Automatic car parking

systems is the sole solution to park as many cars as possible in as little space as

possible. Automatic car parking systems are based on the most modern

technology of storage systems.

Our demonstration facility presents a miniature model of

an automated car parking system that regulates the number of cars that can be

parked in a given space at any given time based on the parking space

availability. Automated parking is a method of parking and exiting cars using

sequence detecting and sensing devices. The entry and exit of vehicles are

facilitated using a totally automated gate. Status signals indicate whether a car is

currently in the process of entering or leaving the parking space. After the initial

installation, the system requires no manual control. It requires no attendants, is

more cost-effective than conventional garages, and allows more cars to be

parked in less space. The automation technology is used to typically double to

triple the capacity of conventional parking garages.

SYSTEM OVERVIEW

A gate has been provided at the entry of the parking

space, which opens on the arrival or departure of a car. A display section has

been provided, which consists of status signals and a display showing the

number of cars present in the parking space at any point of time. After the

maximum number or cars have entered the parking space, the gate is

automatically disabled for vehicles seeking entry into the parking lot. A logic

circuit distinguishes between the cars and persons or two wheelers, so that

persons and two wheelers are not included in the count for cars.

SUBMITTED BY:

o MUHAMMED FAISAL T

o RAKESH KP

o SARATH T S

o SHAUN S SEKHAR

S6, Applied Electronics And Instumentation

BLOCK DIAGRAM

The block diagram presented earlier consists of

transmitter, receiver, de-multiplexer, up-counter, down-counter and display

sections.

The transmitter section comprises of two light emitting

diodes which transmit high power light beams. These light beams are incident

on the receivers, which produce an output of zero volt if the beam received is

uninterrupted and +5V if the beam is interrupted by a car. These receivers are

the Light Detecting Resistors which are arranged in such a manner so as to

detect the light even after the obstacle between the sensor and receiver passes

through. The working of the sensors is based on the voltages across collector,

emitter, and base respectively.

Whenever a car enters the parking area, it interrupts

the light beams in a definite sequence. This sequence is given to the up-count

sequence detector, which generates a high output only if the correct sequence

has been detected. Similarly, when the car leaves the parking area, it generates a

fixed sequence, which is given to the down- count sequence detector. The down

count sequence detector generates a high output only if the correct sequence is

produced by the exiting car. The outputs of the up count and down count blocks

are given to the display section. The display section has a counter and a 7-

segment display along with its driver IC to display the count. Depending on the

sequence detector that generates an actuating signal, the count is either

incremented or decremented.

The outputs shown in the display section are based on the increment and

decrement of the counters. Based on these outputs the actuating signals are used

to enable the different status signal.

The display section also consists of certain status signals. The different status

signals include:

1. A yellow signal to indicate that a car is currently in the process of entering or

leaving the parking space.

2. A green signal to indicate that the parking lot has not reached its maximum

capacity and that space is available for the parking of a car in the parking area.

3. A red signal to indicate that the parking space is full. The activation of this

signal coincides with the disabling of the green signal and consequently closing

of the gate for vehicles trying to enter the parking lot.

Thus the circuit functions regulating the number

of cars that can be parked in a given parking lot at any given time based on the

parking space availability. And also indicates the current status of the parking

lot, be it full, half -filled or vacant .

DISPLAY INDICATION CHART

LED

INDICATION

YELLOW

RED

GREEN

Car in the process of

parking

No vacancy

Parking Space Available

THE CIRCUIT

The automated car parking circuit primarily uses

two LDR’s, two transmitters which are high power LED’s, 74LS74 D flip-flops,

74155 2:4 decoder, up/down counter 74193, seven segment display driver

CD4511, miniature motor driver L293D, NAND gate IC 7400 and NOT gate IC

7404. In addition to these, it has got green, yellow and red LED’s and also a 6V,

500 mA dc motor.

For easy understanding of the circuit, it has been divided into the following four

basic sections.

1. Sensor

2. Sequence detector

3. Counter and display

4. Gate control.

SENSOR SECTION

In this section, we use two transmitters(LED’s) which

generates high power light beams . The signals of which are received by the

receivers of the sensor section.

The receiver section consists of two identical light

detecting resistors. When the signal from the transmitters are received ; a low dc

level (logic low) is obtained at the output. But once the signal is cut ,the output

obtained is at logic high.

The +5V dc level occasionally drops to zero, even

when the signal strength is quite low, due to very high sensitivity of the

receiver. This may lead to the false triggering of the circuit, which must be

eliminated. For this we provide an electrolytic capacitor that is connected

between the output of receiver and ground.

The output of the receiver is obtained due to the fact that

when light falls on this circuit (Fig:-) the resistance value is reduced, which

results in the passage of current through the base turning the transistor ON.

Thus the collector voltage is low and the output obtained is low. But once the

signal is cut the collector voltage level increases ,resulting a high output.

SEQUENCE DETECTOR SECTION

This section is the heart of the entire system. It consists

of a 2:4 decoder and flip-flops, which are used for sequence detection. The

74155 dual 2:4 decoder receives its select signals at pins 13 (A) and 3 (B) from

the receivers LDR1 and LDR2 respectively. The other decoder is not used. The

output lines of the enabled decoder are active low.

For convenience, the receiver before the entrance to the

gate is connected to pin 13 of 74155. In default state, each receiver is active and

inputs zero to the decoder, making the Y0 output line low.

When the first sensor is blocked, the Y1 lines goes

low. The low-going Y2 line indicates that only the second sensor is blocked. A

low Y3 line indicates that both signals have been blocked. Refer truth table of

the IC 74155. The four output lines act as control and decoding signals for the

remaining circuits.

The sequence detection logic circuit consists of three

flip-flops for detecting the incoming as well as the outgoing vehicles. The Y0

line is connected to the clear lines of all the flip-flops, which gives zero at their

respective outputs. The vehicle entering the parking area must interrupt the first

sensor (before entrance), then both the sensors and finally just the second sensor

(after entrance). Thus the sequence generated states are 10, 11 and 01,

necessarily in that sequence.

For identifying the states and the order in which

they occur, we give the Y1, Y3 and Y2 lines after logical inversions to the clock

inputs of the three successive flip-flops, respectively. A Vcc signal is the input

to the first flip-flop, while each subsequent input is the output of the previous

flip-flop. The logic states of the three coded output lines are inverted because

these are active low, while the 74LS74 D flip-flops are triggered by the rising

edge of the clock signals.

Only the proper sequence of logic states will cause

logic high at the output of the third flip-flop. Any other sequence will not allow

the transfer of high signal through the series of flip-flops.

The output of the third flip-flop is given to the counter

and display section, which increments the court. Thus when the vehicle enters

the parking area, the Y0 signal clears all the flip-flops, and at this very instant,

the count is incremented. An identical circuit is used for detecting a vehicle

leaving the parking area. In this case however states generated by the vehicle

are 01, 11 and 10, necessarily in that order. Hence the clock signals for the three

successive flip-flops are derived from Y2, Y3 and Y1 lines respectively.

The working of this circuit is identical to the one for detecting a vehicle entering

the parking area. In this case, the final D flip-flop output is given to the counter

and display section for decrementing the count. This occurs at the instant when

the outputs of the flip-flops are cleared by the low going Y0 signal [The details

of which has been explained in the counter and display section].

COUNTER AND DISPLAY SECTION

This section consists of up/down counter IC 74193,

BCD to 7 segment decoder, display driver IC 4511 (to drive a common cathode

7 segment display) and three LEDs (red, yellow and green).

The counter IC 74193 is capable of handling up as

well as down counts if configured for the same. The count is incremented by

one when a rising edge is encountered on the up pin (pin 5) and decremented by

one when a rising edge is encountered on the down pin (pin 4) of the circuit, the

former occurs when the vehicle has entered the parking area and the line Y0

clears the output of the final flip-flop, causing a transition from the high to low

logic state, which when passed through an inverter, provides a rising edge. The

count decrements in the same fashion as the flip-flops in question are those used

for detecting the vehicles leaving the parking area.

The preset data pins of the counter IC are connected

to Vcc. The four BCD output lines of up/down-counter (74193) are fed to the

corresponding pins of the decoder / driver 4511. The logic circuit inside the

driver IC converts the four-bit BCD input to the output which are active high

suitable to drive the common cathode indication. Thus the active high outputs of

the decoder are connected to the corresponding pins of the 7 segment common

cathode display.

The MSB and LSB lines of the outputs of the counter

are NANDed using the NAND gate. The output of this NAND gate is then

inverted by an inverter gate and then fed to the anode of the red LED, which

indicates that nine vehicles are present in the parking area and there is no further

space. This happens because the output of the binary 9 on the lines makes the

extreme lines high, which gives a high at the otherwise low anode of the red

LED, thus turning it ON. The output of the NAND gate is fed to the anode of

the green LED. The green LED is activated when the count is less than nine,

indicating the availability of space for at least one vehicle in the parking area.

The yellow LED indicates that the vehicle is entering or leaving the parking

area.

Hence, this LED must be ON when at least one of the

sensors is being cut. For this reason, the Y0 line of the decoder is given at the

anode of the LED. When no signal is being cut, the Y0 line is low, keeping the

LED off. But as soon as any of the signals is cut, the Y0 line goes high, turning

the yellow LED ON. The LED indication for various situations is depicted in

table.

GATE CONTROL SECTION

The gate control section consists of the motor driver

IC [L293D] the OR gate and the two D flip-flops which provide appropriate

logic used for controlling the operation of the gate / barrier.

Assume that the lower position of the barrier is the

default position. Now whenever the input to the motor driver IC is 10, it causes

the motor to rotate, thereby causing the barrier to move such that it opens the

entrance. Similarly, when the input to motor driver is 01, the motor rotates in

the opposite direction to lower the barrier, thereby closing the gate. When the

input to the motor driver is 00, the motor does not rotate.

When the car has completely entered the parking area,

the input to the L293D is 01, causing the motor to rotate such that the gate

begins to close. Thus, the movement of the gate is controlled on the arrival or

departure of a car. The table gives us a crystal clear picture of the working of

the gate control section.

In order to disable the gate from opening for a vehicle

entering the parking area after the count of 9, we use a simple combinational

logic circuit consisting of NAND and OR gates, whose output is given to enable

pin 1 of the L293D motor driver. In normal condition, the output of this logic

circuit is high. When the maximum count of 9 is reached, the output of the logic

circuit becomes low, thereby disabling the motor, and keeping the gate closed

for all vehicles seeking entry to the parking area.

However, when a vehicle wishes to leave the area, the

IC gets enabled, thus opening the gate. The output current capability per

channel of L293D is approximately 600 mA. The truth table of L293D is given

in table.

COMPONENT LIST

SEMICONDUCTORS

IC1 - 74LS155 DUAL 2:4 DECODER

IC2 - 7404 HEX INVERTER

IC3 - 7400 NAND GATE

IC4 - 7432 OR GATE

IC5-IC8 - 74LS74 DUAL ‘D’ FLIP FLOP

IC9 - 4511 SEVEN SEGMENT DRIVER

IC10 - 74193 4-BIT UP/DOWN COUNTER

IC11 - L293D PUSH PULL FOUR CHANNEL

MOTOR DRIVER

IC12 - NE 555 TIMER

D1-D2 - IN4148 DIODE

DIS1 - LTS-543 COMMON CATHODE 7 SEGMENT DISPLAY

R3-R4 - 1.8 KILO OHM

R5,R6,R8 - 100 OHM

RESISTORS(1/4 WATT)

R1-R2 - 3.3 KILO OHM

R3-R4 - 1.8 KILO OHM

R5,R6,R8 - 100 OHM

R7,R9 - 1 MEGA OHM

R10-R19 - 330 OHM

MISCELLANEOUS

- 5V, 1A REGULATED POWER SUPPLY

- FLEXIBLE WIRE

- MOTOR UPTO 600mA OUTPUT CONVERT CAPABILITY

CONCLUSION

This project in which we have involved ourselves for the first time

features a lot of facilities, which we are glad to bring out. This circuit is useful

for underground parking, company parking etc. Modifications can be done to

work on pay–and–park scheme. The counter part and display part of the circuit

can be modified to count more than 9. Also it reduces the unregulated parking

with this has encouraged us to try out new circuit ideas and implement them.

TRUTH TABLE OF 74155(IC1}

ENABLE OUTPUTS

PIN 13 PIN3 PIN1 PIN2 PIN7 PIN6 PIN5

PIN4

(A) (B)

E1 E2 Y0 Y1 Y2 Y3

0 0

1 0

1 1

0 1

H L

H L

H L

H L

L H H H

H L H H

H H H L

H H L H