Introduction :-
This handy cell phone detector, pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cellphone from a distance of one and-a-half metres. Therefore it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorised video transmission. Mobile phone detectors can be used to detect the signal on both the incoming and outgoing calls SMS and video transmission even if the phone is kept in silent mode. The moment we press the call button on our mobile phone discontinuous beeps on buzzer are heard with LED blinking and both of them become continuous as the call is connected and continues until the signal transmission stops. An ordinary RF detector using tuned LC circuits is not suitable for detecting signals in the GHz frequency band used in mobile phones. The transmission frequency of mobile phones ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10 cm. So a circuit detecting gigahertz signals is required for a mobile bug which is fulfilled here.


List of components:-

1. C1,C2 22pF

2. C3 0.22µF

3. C4 100µF/16V

4. C5 47pF

5. C6,C7 ,C8 0.1µF

6. C9 4.7µF/16V

7. LED1


9. T1 BC548

10. R1,R3 2.2M

11. R2 100K

12. R4 1K

13. R5 2K

14. R6 15K

15. IC1 CA3130

16. IC2 NE555


Here the circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone.

Op-amp IC CA3130 (IC1) is used in the circuit as a current-to-voltage converter with capacitor C3 connected between its inverting and non-inverting inputs. It is a CMOS version using gate-protected p-channel MOSFET transistors in the input to provide very high input impedance, very low input current and very high speed of performance.

The output CMOS transistor is capable of swinging the output voltage to within 10 mV of either supply voltage terminal.

Capacitor C3 in conjunction with the lead inductance acts as a transmission line that intercepts the signals from the mobile phone. This capacitor creates a field, stores energy and transfers the stored energy in the form of minute current to the inputs of IC1. This will upset the balanced input of IC1 and convert the current into the corresponding output voltage.

Capacitor C4 along with high-value resistor R1 keeps the non-inverting input stable for easy swing of the output to high state. Resistor R2 provides the discharge path for capacitor C4. Feedback resistor R3 makes the inverting input high when the output becomes high. Capacitor C5 (47pF) is connected across ‘strobe’ (pin 8) and ‘null’ inputs (pin 1) of IC1 for phase compensation and gain control to optimize the frequency response.

When the cell phone detector signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers monostable timer IC2 through capacitor C7. Capacitor C6 maintains the base bias of transistor T1 for fast switching action. The low-value timing components R6 and C9 produce very short time delay to avoid audio nuisance.


1. This detector circuit can be used to detect and prevent use of mobile phones in prohibited areas like examination hall, office or some meetings etc.

2. It can be used to find our mobile phone if kept in silent mode in a hard to look area.

3. This can be used by many companies to locate appropriate areas for its tower stands.

4. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission.





  1. This project help you to detect the presence of RF signal..!!!

  2. hello sir,
    i need a small help regarding the components specifications.
    kindly help me with the same by forwarding the info regarding the antenne and the capacitor C3.
    my email id is
    and my contact number is 8802447656.

  3. hello sir ,
    can u snd me d layout of pcb design fr dis ckt diagram...

    my mail id:

  4. hello sir,I need mobile bug using microcontroller..could u pls help me out..
    my email id is

  5. sir i need detector using microcontroller
    email :

  6. Tell me the name of another IC which replace this CA3130 because it is not available in nearby market.

  7. CA3130A and CA3130 are op amps that combine the advantage of both CMOS and bipolar transistors.
    Similar ones are CA 3140, CA 3240 you can used.

  8. hi sir,
    can you send me the pcb layout circuit design?
    my email,
    thanks ya!

  9. Hi,

    can you send me the project report as well as the pcb layout circuit design?

    My mail id:-

  10. Very valuable information and best idea from this blog regarding design of circuits for cell phone detector. Thanks for providing this nice blogs. I appreciate very much .

  11. hello sir,
    can you plz send ,me the calculations of the component values.

  12. This continually is amazing to me how blog owners for example your self can find some time and the dedication to keep on crafting wonderful posts. Your blog is excellent and one of my have to read blogs and forums. I simply wanted to thank you and suggest you to have a look upon this great website which provides best cell phone detector systems to you. Get your personnel cell phone detection and Cell phone detector system legally.

  13. Thanks for the nice blog. It was very useful for me. Keep sharing such ideas in the future as well. This was actually what I was looking for, and I am glad to came here! Thanks for sharing the such information with us.
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  14. I agree with you...the way we look at clown needs to be changed. The experience you had in Japan must be a learning experience for you. Some of the Japanese must have shown hatred buy they must have shown respect to you as well. cell phone detector


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