26-06-2012, 10:31 AM
Home Appliances Control Through IR Remote
Home Appliances Control Through IR Remote.rtf (Size: 54.38 KB / Downloads: 38)
INTRODUCTION
The project is a kind of Embedded system project. The 89c51 micro-controller is used in this system. The logic behind project is to interlace the IK receiver with the controller .
The most of consumer electronics, from camcorders to stereo equipment, an infrared remote control is usually always included. Video and audio apparatus, computers and also lighting installations now a days often operate on infra-red remote control. The carrier frequency of such infra-red signals is typically in the order of around 36 kHz. The control codes are sent in serial format modulated to that 36 KHz, carrier frequency (usually by turning the carrier on and off).
There are many different coding systems in use, and generally different manufacturers use different codes and different data rates for transmission. "IR" stands for infrared. Infrared light is invisible since its frequency is below that of visible red. Otherwise, it is like any other light source, operating under the same laws of physics. In most cases, the IR signals are produced by an LED source. TV remotes send commands only one way, in a low-speed burst for distances of up to 30 feet. They use directed IR with LEDs that have a moderate cone angle to improve ease-of-use characteristics. The IR signal sent out by those devices is generally modulated to around 38 kHz carrier using amplitude shift keying. The data rate send is generally in range of 100-2000 bps.
In this system generally RC5 encoding protocol is used in the transmitting section. On the receiver side a photodiode takes up the signal. The integrated circuit inside a typical receiving chip is sensitive only around a specific frequency in the 32-40 kHz range. The output is the demodulated digital input, the micro controller will sent output to one of its output pin of available 32-I/O pins. To these output pins various home equipments like Bulb, Tube-lights and Fans are interfaced using proper relays or driver circuitry. Some additional facilities such are variable speed control of D.C motor.
I R THEORY
The cheapest way to remotely control a device within a visible range is via Infra-Red light. Almost all audio and video equipment can be controlled this way now a days. Due to this wide spread use the required components are quite cheap, thus making it ideal for us hobbyists to use IR control for our own projects.
There are some IR systems which use other frequencies and other modulation systems. IR transmit and receive systems are inexpensive and are generally reliable. Interference can also be caused by other light sources such as fluorescent lights.
Sometimes some electronic ballasts powered light can cause interference problems. In order to avoid any interference with this kind of equipment, the operating frequency of all electronic ballasts has to be chosen at around 36-40 kHz (this is the frequency of the IR carrier and should not to be confused with the actual frequency of the IR light itself). The possibility of interference is more likely around the 40 kHz frequency. Some IR systems now use carrier frequencies into the megahertz region. Generally infrared remote controls are a 32-40 kHz modulated square wave for communication. This square wave is then send to IR transmitter (IR LED).
Infra-Red actually is normal light with a particular colour. We humans can't see this colour because its wave length of 950nm is below the visible spectrum. That's one of the reasons why IR is chosen for remote control purposes, we want to use it but we're not interested in seeing it. Another reason is because IR LEDs are quite easy to make, and therefore can be very cheap
Although we humans can't see the Infra-Red light emitted from a remote
Although we humans can't sec the In Infra-red light emitted from a remote control doesn’t mean we can’t make it visible.
A video camera or digital photo camera can "see" the Infra-Red light as you can see in this picture. If you own a web cam you're in luck, point your remote to it, press any button and you'll sec the LFT) flicker. Unfortunately for us there are many more sources of Infra-Red light. The sun is the brightest source of all but there are many others, like: light bulbs, candles, central heating system, and even our body radiates Infra-Red light. In fact everything that radiates heat, also radiates Infra-Red light. Therefore we have to take some precautions to guarantee that our 1R message gets across to the receiver without errors.
On the receiver side a photodiode takes up the signal. The integrated circuit inside a typical receiving chip is sensitive only around a specific frequency in the 32-40 kHz range. The output is the demodulated digital input, just what was used to drive the transmitter. Usually this kind of receivers work so that when IR the carrier is present, this output is high.