Automatic Car Parking System
MUHAMMED FAISAL T
SARATH T S
SHAUN S SEKHAR
S6, Applied Electronics And Instumentation
College Of Engineering, Trivandrum
Automatic car parking System.doc (Size: 610.5 KB / Downloads: 1033)
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.
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.
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
Car in the process of parking
Parking Space Available
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.
3.Counter and display
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.
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
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
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
5V, 1A REGULATED POWER SUPPLY
- MOTOR UPTO 600mA OUTPUT CONVERT CAPABILITY
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.