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project report

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Arqum Saleem

on 11 October 2013

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Transcript of project report

Light / Dark Sensor
A sensor that is activated by the change in the intensity of light in the surrounding
Topics To Be present
A few Jumper Wires
9 Volts Battery
9 Volts Battery Clip
Light Dependent Resistor (LDR)
Light Emitting Diode (LED) with any color of choice
3362P-103-ND 10K Ohms Variable Resistor
1K Ohms (Brown-Black-Red) Resistor X2
330 Ohms (Orange-Orange-Brown) Resistor
Automatic dark detector senses darkness. As the light level decreases and LDR meets the maximum threshold resistance, the circuit automatically switches on the bulb attached to it.To make this circuit operate in reverse (the LED turns on when there is light), simply just exchange the positions of the Variable Resistor and the LDR.
A breadboard (or protoboard) is usually a construction base for prototyping of electronics. The term "breadboard" is commonly used to refer to a solderless breadboard (plugboard).
LDR / Photoresistors
A photoresistor or light dependent resistor (LDR) is a resistor whose resistance decreases with increasing incident light intensity; they are used in many consumer products to determine the intensity of light.
A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.
A simple light sensor may be part of a security or safety device, such as a burglar alarm or garage door opener. These types of devices often work by shining a beam of light from one sensor to another; if the light is interrupted, an alarm sounds or the garage door won't close.
Light detectors are one of the most popular sensor and they are commonly found in many real-world applications. They are widely used by electronic hobbyists and projects because they are practical and intriguing yet surprisingly easy to construct.
Many modern electronics, such as computers, wireless phones, and televisions, use ambient light sensors to automatically control the brightness of a screen, especially in low-light or high-light situations. They can detect how much light is in a room and raise or lower the brightness to a more comfortable level for the user. Light sensors also may be used to automatically turn on lights inside or outside a home or business at dark.
Like its name suggests, a comparator compares two given voltages. The pair of 1K ohms resistors create a voltage divider and provide a 4.5 volts reference for the comparator. The variable resistor and LDR both form another pair for a second voltage divider. When light falls on the LDR, its resistance lowers and that voltage divider provides a voltage lower than 4.5 volts. The comparator produces no output (0 volts). When light is absent, the resistance of the LDR and the voltage increases. When the voltage increases over 4.5, the comparator activates its output and supplies 9 volts to power the LED.
A direct application of the circuit would be to turn on a night light as your room light goes out or to keep a porch light on during the night.

Barcode scanners found in most retailer locations work using light sensor technology.

Light sensors continue to have many uses in science, from the simplest science fair experiments to the latest breakthroughs in space, medicine, and robotics.
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