MOBILE PHONE DETECTOR PROJECT GUIDE Mr.M.Manikandan Asst Professor(ECE) PRESENTED BY P.Salini Sebasty G.Sangeetha K.Sherine Weeber

CONTENTS Objective Introduction Basic Principle Circuit diagram. Components. Circuit design. Mobile phone tracking operation. Applications. Limitations of mobile phone detector circuit.

OBJECTIVE To detect the presence of an activated mobile phone. For detecting the use of mobile phone for spying and unauthorized video transmission.

INTRODUCTION With advancement in communication technology, the requirement of cell phones has increased manifold. This project is used to develop a mobile detector that can sense the presence of an activated mobile phone. The moment the circuit detects RF transmission signal from an activated mobile phone the LED blinks. The LED continues to blink until the signal transmission ceases.

BASIC PRINCIPLE The basic principle behind the circuit is the idea of using a schottky diode to detect the cell phone signal. Schottky diodes rectifies low frequency signals with low noise rate. The low power signal can be amplified and used to power any indicator like an LED in this case.

Mobile Phone Detector Circuit CIRCUIT DIAGRAM Mobile Phone Detector Circuit

CIRCUIT COMPONENTS V1 = 12V L1 = 10uH R1 = 100Ohms C1 = 100nF R2 = 100K R3 = 3K Q1 = BC547 R4 = 200 Ohms R5 = 100 Ohms IC1= LM339 R6 = 10 Ohms LED = Blue LED

CIRCUIT DESIGN DETECTOR CIRCUIT: The detector circuit consists of an inductor, diode, a capacitor and a resistor. COMPARATOR CIRCUIT: LM339 is used as a comparator . The reference voltage is set at the inverting terminal using a potential divider arrangement. AMPLIFIER CIRCUIT: A simple BJT BC547 is used in a common emitter mode. The battery voltage is 12V .the operating point collector emitter voltage is 5V and collector current is 2mA.

LM339 PIN DIAGRAM

MOBILE PHONE TRACKING OPERATION When a mobile phone is present near the signal, a voltage is induced in the choke and the signal is demodulated by the diode. This input voltage is amplified by the common emitter transistor. The output voltage is more than the reference output voltage producing a logic high signal and the LED starts glowing, to indicate the presence of a mobile phone. The circuit has to be placed centimeters away from the object to be detected.

APPLICATIONS Petrol pumps Gas station Historical places Religious places Court of laws Examination halls Spying and unauthorized video transmission Military bases Hospitals Theatres Conferences Embassies

LIMITATIONS OF MOBILE PHONE DETECTOR It is a low range detector , of the order of centimeters. The schottky diode with higher barrier height is less sensitive to small signals

FUTURE SCOPE: Trying to increase the detecting range of mobile from centimeters to few meters. This can be achieved using either microcontroller or a 555 Timer.

Thank you