KALASALINGAM UNIVERSITYDepartment of Electronics and Communication Engineering AUTOMATIC STREET LIGHT CIRCUIT SUBMITTED BY GUIDED BYAbhishek (9911005002) Mr.M.K.ParmathmaAjith Kumar(9911005005) Assistant Professor ECE ,KLU 1
OVERVIEW OF MINI PROJECT 2• The main purpose of designing this project is to prevent loss of current unnecessarily during day time.• During night the bulb will automatically glow .
ABSTRACT A street light that automatically switches ON when the night falls and turns OFF when the sun rises. In fact we can use this circuit for implementing any type of automatic night light. The circuit uses a LDR to sense the light . When there is light the resistance of LDR will be low. So the voltage drop across POT R2 will be high.This keeps the transistor Q1 ON. The collector of Q1(BC107) is coupled to base of Q2(SL100). So Q2 will be OFF and so do the relay. The bulb will remain OFF. When night falls the resistance of LDR increases to make the voltage across the POT R2 to decrease below 0.6V. This makes transistor Q1 OFF which in turn makes Q2 ON. The relay will be energized and the bulb will glow. 4
7 Relay is an electromagnetic device which is used to isolate two circuits electrically and connect them magnetically. They are very useful devices and allow one circuit to switch another one while they are completely separate. They are often used to interface an electronic circuit (working at a low voltage) to an electrical circuit which works at very high voltage. For example, a relay can make a 5V DC battery circuit to switch a 230V AC mains circuit. Thus a small sensor circuit can drive, say, a fan or an electric bulb. A relay switch can be divided into two parts: input and output.
VOLTAGE REGULATOR 8 It is a voltage regulator (7805) integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide. It provides +9V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.
FUSE[1A] 9 Fuse is an electronics safety device placed in a circuit consisting of a replaceable plug or tube containing wire or metal that will melt and break the circuit if the current exceeds a specified amperage. Blow a fuse: to cause an electrical fuse to melt.
LIGHT DEPENDENT RESISTOR 10 An LDR (Light dependent resistor), as its name suggests, offers resistance in response to the ambient light. The resistance decreases as the intensity of incident light increases, and vice versa. In the absence of light, LDR exhibits a resistance of the order of mega- ohms which decreases to few hundred ohms in the presence of light. It can act as a sensor, since a varying voltage drop can be obtained in accordance with the varying light. It is made up of cadmium sulphide (CdS). An LDR has a zigzag cadmium sulphide track. It is a bilateral device, i.e., conducts in both directions in same fashion.
RESISTOR 11 Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits. Resistors can be either fixed or variable. The low power resistors are comparatively smaller in size than high power resistors.
TRANSISTOR 12 BC107 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current. A small current at its base controls a larger current at collector & emitter terminals. BC107 is mainly used for amplification and switching purposes. It has a maximum current gain of 800. The transistor terminals require a fixed DC voltage to operate in the desired region of its characteristic curves. This is known as the biasing. The voltage divider is the commonly used biasing mode. For switching applications, transistor is biased so that it remains fully on if there is a signal at its base. In the absence of base signal, it gets completely off.
TRANSISTOR[SL100] 13 SL100 is a general purpose, medium power NPN transistor. It is mostly used as switch in common emitter configuration. The transistor terminals require a fixed DC voltage to operate in the desired region of its characteristic curves. This is known as the biasing. For switching applications, SL100 is biased in such a way that it remains fully on if there is a signal at its base. In the absence of base signal, it gets turned off completely. The emitter leg of SL100 is indicated by a protruding edge in the transistor case. The base is nearest to the emitter while collector lies at other extreme of the casing.
BATTERY 14 It is a collection of one or more electrochemical cells in which stored chemical energy is converted into electrical energy. One half cell houses the Anode to which the positive ions migrate from the Electrolyte and the other houses the Cathode to which the negative ones drift. The two cells are may be connected via a semi permeable membranous structure allowing ions to flow but not the mixing of electrolytes as in the case of most primary cells or in the same solution as in secondary cells. The performance of the cell continues to dip gradually as the concentration of ions in the solutions decrease, marked by an increase in internal resistance eventually leading to the exhaustion of the battery.