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

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

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

4. 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.

5. 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.

6. Mobile Phone Detector Circuit
CIRCUIT DIAGRAM
Mobile Phone Detector Circuit

7. 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

8. 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.

9. LM339 PIN DIAGRAM

10. 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.

12. 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

13. 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

14. 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.

15. Thank you