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Speed Checkers for Highways

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1. INTRODUCTIONMany analysts and policy makers have argued that building more highways is an Ineffective response to congestion: specifically, that it is infeasible to add enough highways Capacity in large urban areas to provide much relief. But this making of highways is just showing the path for accidents because of no speed limits in these highways. In order to overcome this problem we have designed equipment called as SPEED CHECKER ON HIGHWAYS. This kit investigates differentiated design standards as a source of capacity additions that are more affordable. Here we consider the average speed and high speed with which the vehicles are moving. We also consider the implications of differing accident rates. All these consideration were taken and the design of this equipment is done. This design helps to find the vehicles which are moving with high speed in spite of a speed limit board is present in that highway. The cops then can take necessary action on that culprit. The design mainly uses a timer, counter, logic gates and 7-segment display. Using these components we design the speed checker on highways and observed that it is working more efficiently than expected.



Fig 2.1 Block Diagram

2.2 Block DescriptionThere are totally four sections in the block diagram. They are Counter circuit, timer & control circuit, triggering circuit and 7-segment display. Each block has its own functionality. The 7-segment display is used for displaying the output. The counter circuit is the one count the number of times an event has occurred in accordance with the clock signal. The is received from the timer and control circuit. The timer and control circuit consists of a timer IC and another IC which receives input signal from triggering circuit according to the ON/OFF condition of the two switches present there. A circuit having a delay circuit provided with a gate for converting the output signal of an SR flip-flop into a signal with a delay equal to or more than the clock pulse width enough for count


operation and leading the logical addition between the signal and system clock and the logical multiplication between the signal and counter write signal to the direct reset input of a transparent latch 7 and for realizing read-on-the-fly or write-on-the-fly operation even if timer input does not synchronize with the system clock is called as Timer & Control circuit. A circuit or network in which the output changes abruptly with an infinitesimal change in input at a predetermined operating point. Also known as trigger. A circuit in which an action is initiated by an input pulse.


Fig 2.3 Circuit Diagram



Fig 2.3.1 Main Circuit Diagram

2.4 circuit Operation:The circuit mainly consists of a supply circuit, control circuit and a 7-segment display. The control circuit consists of a counter ON/OFF circuit, timer & control circuit amd triggering circuits connected to the switches. When a supply is given to the secondary of the transformer, it steps down the 220v AC supply to 18v AC. This 18v is fed to the bridge rectifier in order to convert AC to DC. The bridge rectifier provides same polarity of output voltage for either polarity of input voltage. Its most common application is conversion of AC input to DC output. A capacitor is connected across the output of bridge rectifier in order to reduce noise and fluctuations in the output voltage. The 18v dc acts as input to the voltage regulator which reduces the voltage to 12v,as only 12v is required to the circuit. This regulator uses a resistor to maintain the voltage constant throughout the operation. This voltage is now fed to the whole circuit.


The kit mainly consists of two laser transmitter-LDR sensor pairs which are installed on the highway 100m apart such that the transmitter and LDR sensor of each pair on the opposite sides of the road. This kind of arrangement is shown in the figure below.

Fig 2.4 Circuit Operation When any vehicle crosses the first laser beam LDR1 goes high for the time set to cross 100mts with the selected speed (60KMPH) and LED1 glows during this period. When the vehicle crosses the second laser light beam, the output of IC2 goes high and LED2 glows for this period. Pezo buzzer sounds an alarm if the vehicle crosses the distance between the laser setups at more than selected speed(lesser period than preset period).The counter starts counting when the first laser beam is intercepted and stops when the second laser beam is intercepted. The time taken by the vehicle to crop both the laser beams is displayed on the 7segment display.

2.5 Supply Details:Input supply to the transformer Input supply to the Bridge Rectifier Input supply to the Regulator Supply to the PCB 220v AC 18v AC 18v DC 12v DC


3 COMPONENT DESCRIPTION 3.1 Transformer:Transformer is static equipment which transforms power from one circuit to another by stepping up or stepping down the primary voltage without any change in the frequency.

Fig 3.1 Transformer A transformer is an energy device it has an input side (primary) and an output side (secondary).electrical energy applied to the primary is converted to a magnetic field which in turn, induces a current in the secondary which carries energy to the load connected to the load connected to the secondary. The alternating current that flows through the primary winding establishes a time varying magnetic flux, some of which links to the secondary winding and induces a voltage across it. The magnetic of this voltage is proportional to the number of turns on the primary winding to the number of turns on the secondary winding this is known as turns ratio. The basic working principle of transformer is based on mutual induction between two coupled coils. According to this principle by changing flux creates on induced emf in turn equal to the derivative of the flux so that the total induced emf across N turns is


E= N [email protected]/dt

:- (@=fi)

A transformer consists of at least two sets of windings wound on a single magnetic core. There are two main purposes for using transformers. The first is to convert the energy on the primary side to a different voltage level on the secondary side. This is accomplished by using differing turns counts on primary and secondary windings. The voltage ratio is the same as the turns ratio. The second purpose is to isolate the energy source from the destination, either for personal safety, or to allow a voltage offset between the source and load.

Fig 3.1.1 Step Down Transformer A step down transformer has less turns of wire on the secondary coil which makes a smaller induced voltage in the secondary coil. Decreasing the voltage does not decrease the power. As the voltage goes down, the current goes up. It is called a step down transformer because the voltage output is smaller than the voltage input. If the secondary coil has half as many turns of wire then the output voltage will be half the input voltage.

3.2 RectifierRectifier circuits are found in all dc power supplies that operate from an ac voltage source. They convert the ac input voltage to a pulsating dc voltage. The most basic type of rectifier circuit is the half-wave rectifier. Although half-wave rectifiers have some applications,


the full-wave rectifiers are the most commonly used type in dc power supplies. These are two types of full-wave rectifiers: (1) full-wave center-tapped rectifier (2) full-wave bridge rectifier Here in this particular design we are using a bridge rectifier which is discussed as follows.

3.2.1 Full-wave Bridge RectifierThe full wave bridge rectifier uses four diodes, as shown in below figure. When the input cycle is positive, diodes D1 and D2 are forward-biased and conduct current through RL. During this time, diodes D3 and D4 are reverse-biased.


D3 Vin D2





Fig 3.2 Full-wave Bridge Rectifier During positive half-cycles of the input, D1 and D2 are forward-biased and conduct current, D3 and D4 are reverse-biased. When the input cycle is negative as shown in below figure, diodes D3 and D4 are forward-biased and conduct current in the same direction through RL as during the positive


half-cycle. During the negative half-cycle, D1 and D2 are reverse-biased. A full-wave rectifier output voltage appears across RL as a result of this action.


Vin +









During negative half-cycles of the input, D3 and D4 are forward-biased and conduct current D1 and D2 are reverse-biased. The above two figures explain the full-wave Bridge Rectifier. The output graph of a full-wave rectifier is as shown

below : Fig 3.2.1 Diode Operation and waveform of current


3.2.2 IN4007 DiodeThese diodes are used to convert AC into DC these are used as half wave rectifier or full wave rectifier. Three points must he kept in mind while using any type of diode. 1. Maximum forward current capacity 2. Maximum reverse voltage capacity 3. Maximum forward voltage capacity

Fig 3.2.2 IN4007 Diode The number and voltage capacity of some of the important diodes available in the market are as follows:

Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 have maximum reverse bias voltage capacity of 50V and maximum forward current capacity of 1 Amp.

Diode of same capacities can be used in place of one another. Besides this diode of more capacity can be used in place of diode of low capacity but diode of low capacity cannot be

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