Wednesday, December 9, 2015

Wireless Charging System

Posted By: Unknown - 9:29 AM
Mobile phones becoming a basic part of life, the recharging of mobile phone batteries has always been a problem. The mobile phones vary in their talk time and battery stand by according to their manufacturer and batteries. All these phones irrespective of their manufacturer and batteries have to be put to recharge after the battery has drained out. The main objective of this current proposal is to make the recharging of the mobile phones independent of their manufacturer and battery make.Now we will explain it by using induction principle.This is based on Inductive charging uses an electromagnetic field to transfer energy between two objects. This is usually done with a charging station. Energy is sent through inductive coupling to an electrical device, which then can use that energy to charge batteries. Because there is a small gap between the two coils employed in each of the sender and receiver of the energy within the respective devices, inductive charging is considered a short distance wireless energy transfer, despite the fact that there are typically more wires used with inductive charging than direct contact charging, because it frees the user from having to deal with wires between the two devices. Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery.Use of embedded technology makes this system efficient and reliable. Micro controller (AT89S52) allows dynamic and faster control. Liquid crystal display (LCD) makes the system user-friendly. AT89S52 micro controller is the heart of the circuit as it controls all the functions.

The project is used in multiple ways such as in securing the mobile from loss or theft as well as it gets charged wirelessly. If any one wants to steal it automatically a 60 Db siren will get a switched ON. The system is provided with a control switch it has to be made ON such as if the user wants to charge mobile it will be placed on this inductive plates .Once the charging is completed if it is removed without making the switch OFF automatically siren will be alerted.An alternative charger circuit is also provided to charge the mobile by house hold general purpose 230V in the absence of the induction. This charge circuit uses regulated 5V, 750mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of secondary of 230/18v step down transformer.




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Bluetooth Technology

Posted By: Unknown - 9:15 AM
Bluetooth technology, developed by Ericsson Mobile Communications, a worldwide telecommunications company based in Sweden, is fast becoming the worldwide standard for short-range wireless communication. The technology was originally developed to easily connect cell phones with peripheral devices such as personal computers. However, other potential applications for home and office quickly emerged.Bluetooth is growing so rapidly that Merrill Lynch predicts that by 2005 there will be more than 2.1 billion Bluetooth compatible devices on the market. 

Bluetooth uses Radio Frequencies to transmit and receive signals in the ISM Band. This is an unlicensed frequency range operating between 2.4 and 2.48 GHz.In order to prevent interference with other devices, Bluetooth employs a spread spectrum frequency hopping technique which takes a narrow band signal and spreads it over a broader portion of the available radio frequency band. This spreading is accomplished by frequency-hopping, a technique developed for encryption that relies on the sender and receiver agreeing on a predefined “hop” sequence for frequency variation. Since only the intended receiver is aware of the transmitter’s hopping pattern, only that receiver can make sense of the data being transmitted. Spread spectrum frequency hopping ensures Bluetooth’s security and limits interference.


The Bluetooth 1.0 specification allows for a gross data transfer rate of 1 Mbps. However, this is a theoretical maximum for half-duplex data transmission. Full duplex transmission is accomplished at 432.6 Kbps. The Bluetooth specification can support three synchronous voice channels at 64 Kbps each. Bluetooth devices typically require 1 mw of power to operate. When two Bluetooth devices establish a connection, they create a network called a piconet. A Bluetooth piconet can contain up to eight Bluetooth devices, with one device serving as a master and up to seven serving as slaves . All devices in a piconet share the same frequency-hopping scheme, which is established when a slave first connects to a master. Bluetooth devices can operate in either a single slave piconet, in which a master connects to only one slave, multi slave piconet, where a master connects to multiple slaves, or in a scatter-net structure. A scatter-net is enabled by masters and slaves with capability to connect to more than one device at a time
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