Basic Electronics

Presented to: Prof. Najaf Name Roll Number M.Mohsin Ijaz 110 Class: Electronics Presented to: Prof. Najaf

Project Topic Light Sensor

Introduction Light sensor is a simple powerful concept. It automatically switches ON lights when the sunlight goes below the visible region of our eyes and automatically switches OFF lights when Sunlight fall on it (in morning), by using a sensor called LDR (Light Dependent Resistor) which senses the light just like our eyes.

Circuit Diagram

Components Light Dependent Resistor (LDR) Integrated Circuit (IC) Variable Resistor Resistance Transistor Diode Relay

Light Dependent Resistor (LDR) A photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity. In other words, it exhibits photoconductivity. A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-activated switching circuits.

Integrated Circuit (IC) Integrated circuits are also called microprocessor chips which contains million of semi conductor devices and small circuit combine together on a single silicon wafer. ICs have two main advantages over discrete circuit, cost and performance.

Variable Resistor A potentiometer informally a pot, that have three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. It is used for measuring electric potential (voltage). For example in electrical device such as volume controls on audio equipment, in a joystick or to control significant power.

Resistance Electrical resistance, a measure of the degree to which conductor opposes an electric current through that conductor. R=V/I If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behaviour of the material.

Transistor A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals (Collector, Base and Emitter ) for connection to an external circuit. 

Diode A diode is a specialized electronic component with two electrodes called the anode and the cathode. Most diodes are made with semiconductor materials such as silicon, germanium, or selenium. Some diodes are comprised of metal electrodes in a chamber evacuated or filled with a pure elemental gas at low pressure. Diodes can be used as rectifiers, signal limiters, voltage regulators, switches, signal modulators, signal mixers, signal demodulators, and oscillators.

Relay A relay is an electrically operated switch. It allows one circuit to switch a second circuit which is completely separated from the first. The output from the driver IC is send to the corresponding relays which thus results in its excitation and gets activated. As a result it controls the corresponding home appliance.

Applications Street lamps Alarm clocks Home lawn and Parks Burglar alarms Camera light meters Light intensity meters