Frequency domain & time domain representations

*TIME DOMAIN REPRESENTATION

It is the representation with signal amplitude on the vertical axis and with time on the horizontal axis - (an oscilloscope diagram). This is sometimes referred to as the "time domain representation".
*FREQUENCY DOMAIN REPRESENTATION

Its the representation with signal amplitude on the vertical axis but with frequency on horizontal axis - a Spectrum Diagram. This is sometimes referred to as the "frequency domain".

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LDR :-Light dependent resistors

A Light Dependent Resistor ( LDR, photoconductor, or photocell) is a device which has a resistance which varies according to the amount of light falling on its surface. They will be having a resistance of 1 MOhm in total darkness, and a resistance of a 1 to 10 of kOhm in bright light. A photoelectric device can be either intrinsic or extrinsic. Applications: An LDR can even be used in a simple remote control circuit using the backlight of a mobile phone to turn on a device - call the mobile from anywhere in the world, it lights up the LDR, and lighting can be turned on remotely! Light Dependent Resistor Circuits: There are two basic circuits using light dependent resistors - the first is activated by darkness, the second is activated by light. In the circuit diagram on the left , the led lights up whenever the LDR is in darkness . The 10K variable resistor is used to fine-tune the level of darkness required before the LED lights up. The 10K standard resistor can be changed as require...

RING BASED HOME AUTOMATION SYSTEM

The project, Ring based home automation system, aims at controlling the status of devices using series of missed calls made to a land phone. The system can either turn on or off any number of devices. Any device either electrical or electronic or both may be controlled, which makes the system ideal for offices or factories also. The mode of operation and the device itself is selected using missed calls only. Since no call is connected, there is no operational cost for the system baring the power losses. Three sets of missed calls must be made; the first one is for activating the system which also acts as a password for the system. The second set is for selecting the mode of operation and the third one is for selecting the device to be controlled. Even though automatic systems are common, it has not taken to a level to control simple operations such as controlling the electrical appliances of a home, but this system will be a difference. The system is cheapest and easiest automation sol...

VIRTUAL KEYBOARD

The Virtual Laser Keyboard (VKB) is a revolutionary accessory (The only keyboard that operates in total darkness - see the picture below) for Blackberry, Smartphone, PDA, MAC & Tablet PC. These are virtual keyboards that can be projected and touched on any surface. The keyboard watches your fingers move and translates that action into keystrokes in the device. Most systems can also function as a virtual mouse. Keyboard projector A holographic element illuminated by a red diode laser produces a template of the keyboard. Illumination Module An infrared plane of invisible light is generated just above and parallel to the surface of the keyboard.When a key is touched light is reflected from this plane and directed towards the sensor module. Sensor module Reflected light from the illumination module is passed through an infrared filter and imaged on to a sensor chip which determines the location of the light.It can process and interpret several keystrokes simultaneously. Working The dev...

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