This document describes a cell phone detector circuit that uses a CA3130 IC and 0.22 μF capacitor to sense radio frequency signals from activated cell phones within 1.5 meters. When the circuit detects an RF signal, the capacitor releases energy to the IC, causing the output to go high and the LED to blink until the signal ceases. The detector can find use in places where cell phones should be silenced like exam halls, hospitals, and courts.

1. CELL PHONE DETECTOR
Compiled and Presented by:
Irene Lalhminghlui- 510615018
Subhajit Dutta -510615007
Priyadeep Biswas- 510615015
Ranapratap Majee- 510615001
Gaurab Bhowmik -510615009
Somdutta Tikadar- 510615012

2. OVERVIEW:
WHAT IS A CELL PHONE DETECTOR?
CIRCUIT DIAGRAM
WORKING OF CIRCUIT COMPONENTS
WORKING PRINCIPLE
APPLICATIONS OF THE DEVICE
CONCLUSIONS

3. WHAT IS A CELL PHONE DETECTOR?
This handy cell phone detector can sense the
presence of an activated cell phone from a
distance of one and a-half meters.
It can detect both the incoming and outgoing
calls, SMS and video transmission even if the
cell phone is kept in silent mode. The moment
the bug detects RF transmission signal from an
activated cell phone, the LED starts blinking,
until signal transmission ceases.

4. CIRCUIT DIAGRAM:

5. WORKING OF CIRCUIT COMPONENTS
LINE VEROBOARD :
 Line Vero is used in this circuit.
CA3130 IC :
 CMOS version gate-protected p-channel MOSFET.
 Acts as an Differential Amplifier.
 Used in the circuit as a Current to Voltage converter.
 Provides very high input impedance , very low input
current and very high speed of performance.

6. 1 kΩ RESISTOR:
 Colour code sequence Brown, Black, Yellow, Gold.
 Keeps the non-inverting input stable for
easy swing of the output to high state.
100 KΩ RESISTOR:
 Colour code sequence Brown, Black, Yellow,
Gold.
 Provides the discharge path for 0.22 µF
Capacitor.

7. 0.22 µF CAPACITOR :
 Ceramic capacitor type.
 Acts as a small gigahertz (GHz) loop
antenna to collect the RF signals from the mobile phone.
 The lead length of the is 18 mm with a spacing of 8 mm
between the leads to get the desired frequency.
100 µF CAPACITOR :
 Electrolytic Capacitor.

8. BC548 TRANSISTOR :
 n-p-n type epitaxial silicon transistor.
 B indicates the material silicon and C stands
for low audio frequency.
 Mainly use for switching and amplification purposes.
9 V BATTERY :
 Rectangular prism shape with round edges
and a polarized snap connector at the top.
 This type is commonly used in walkie talkies,
clocks and smoke detectors.

9. BATTERY CLIP :
 Necessary for holding the battery into place.
 Keep in mind the polarity, while using a battery clip.
LED :
 Light Emitting Diode with two lead
semiconductor light source.
 It is a p-n junction diode, which emits
light when activated.
 We have also used connecting wires.

10. 2.2 MΩ RESISTOR :
 Colour code: Red, Red, Green and Gold.
 Makes the inverting input high when
Output become high.
47 pF CAPACITOR :
 Ceramic Capacitor acts as the dielectric.
 Connected across strobe (pin 8) and null
Input (pin 1) of the IC.
 For phase-composition and gain control to
optimize the frequency response.

11. WORKING PRINCIPLE :
Ordinary LC (Coil-Capacitor) circuits are
used to detect low frequency radiation in
the AM and FM bands . It can detect
maximum MHz frequency.
From Mobile phone we get frequency in terms
of GHz.

12. WORKING PRINCIPLE :
The transmission frequency of mobile phone
ranges from 0.9 to 3 GHz with wave length of 3.3
to 10 cm.
So a circuit detecting GHz signals is required.
Here 0.22 µF disk capacitor is used to capture the
RF signals from the mobile phone. This along with
the leads act as a small GHz loop antenna to
collect the RF signals.

13. WORKING PRINCIPLE :
One lead of the capacitor gets DC from the
positive rail and the other lead goes to the
negative input of IC.
The capacitor gets energy for storage. This energy
is applied to the input of the IC . So the inputs of
IC is almost balanced and output is almost zero.
But at any time IC can give a high output if a small
current is induced to its inputs.

14. WORKING PRINCIPLE :
 There is a natural electromagnetic field around the
capacitor caused by the 50Hz from electrical wiring.
When the mobile phone radiates high frequency
radiation, capacitor oscillates and release energy in
the inputs of IC. This oscillation is indicated by the
flashing of the LED.

15. WORKING PRINCIPLE :
In short, capacitor carries energy and is in an
electromagnetic field. So a slight change in
field caused by the RF signals from phone will
disturb the field and forces the capacitor to
release energy.
The LED blinks until the signal ceases.

16. APPLICATIONS OF CELL PHONE DETECTOR:
 This circuit can be used to detect the presence of active cell
phones at examination halls and meetings.
 It can be used to detect active cell phones in Hospitals, Petrol
pumps, Court of law and Military bases.

17. CONCLUSIONS:
Though the device is handy, it has its own pros and cons just
like other devices.
Pros:
 The device is sensitive to even channelize other RF signals
belonging to other devices other than cell phones like radios.
 It can be used for detecting cell phones used for spying and
transmission of unauthorized audios and videos.

18. THANK YOU
Cons:
 It is a short range detector, of the order of centimeters.
 The presence of this device would jam the signals of other
devices due to the fluctuations.