The main objective of the term paper is to protect your mobile phone from unauthorized use or theft using this simple circuit It can generate a loud chirping sound when somebody attempts to take away the mobile handset. The added feature is that the circuit also works as a mobile charger.
Here we consider the operation of monostable and Astable multivibrators to perform our task. The circuit is powered by a step-down transformer X1 with rectifier diodes D1 and D2 and filter capacitance�s. Even the circuit can also be powered by direct dc supply of 12-15V. The circuit uses two NE555 timers, one to perform astable and other to perform monostable operations.
The output of monostable is given to astable. The output frequency of the monostable is adjusted using preset VR1 such that it is slightly less than that of the astable. This makes the circuit standby, when there is no hand capacitance present. When a hand comes near the shield or makes contact with the shield, which introduces hand capacitance in the circuit. As a result, the astable�s frequency changes, which makes the trigger pin of the monostable low and its output oscillates. This produces chirping sound from the buzzer and also makes the LED1 blink. The circuit can also be used as a mobile charger. It provides output of 6V at 180 mA through regulator IC 7806 (IC4) and resistorR5 for charging the mobile phone.
authors: R.VYSHNAVI (Btech RVR&JC COLLEGE OF ENGG.) G.UDAY (Btech RVR&JC COLLEGE OF ENGG.) A.VIJAY BABU (Btech RVR&JC COLLEGE OF ENGG.) T.KISHORE (Btech RVR&JC COLLEGE OF ENGG.) I sincerely thank authors,the students of "RVR&JC COLLEGE OF ENGG" for their great support. my special thanks to v.v.m.m.rao
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