Hidden Active Cell Phone Detector Circuit and Its Working

The rapid growth of cell phones in the 21st century to now has raised many problems. In addition, public reaction was growing against the disturbance of cell phones introduced in daily life. Here is a simple engineering project, namely the hidden active cell phone detector. The pocket-sized cell phone detector can detect the hidden active cell phone. So this project is used to neglect the use of cell phones in exam halls, private rooms, defense establishments, hospitals, military camps, petrol pumps and also very useful for sensing the use of mobile phones for spying and other correlated activities. This circuit can detect calls, SMS, video transmission even when the cell phone is hidden in silent mode. The prompt bug detects radio frequency transmission signal (RF) from a cell phone, it generates a beep sound alarm.

Hidden Active Cell Phone Detector Circuit

The transmission frequency of cell phones ranges from 0.9Hz -3GHz with a 3.3cm -10cm wavelength. RF signals can be collected from the cell phone along with the disk capacitor and the leads which act as a small gigahertz loop antenna. When the cell phone is triggered, it transfers the signal in a sine waveform which permits through space. The circuit diagram of the hidden active cell phone detector is built with an operational amplifier, monostable multivibrator, and piezo buzzer.

Operational Amplifier

• The input of the operational amplifier is antenna signal and the op-amp consists of 8-pins.
• Op-amp is an integrated circuit and it consists of two inputs with opposite polarities.
• The o/p signal of the operational amplifier is very high when compared to the input signal and the main function of the op-amp is to perform arithmetic operations on an analog circuit.

Monostable Multivibrator

• The output signal of the operational amplifier is fed to a monostable multivibrator. The main function of this multivibrator is to generate a single pulse.
• In this mode of operation, one state of the o/p is balanced and another state of o/p is in unbalanced mode.
• This multivibrator is activated when a logic low signal is given to the i/p and a high logic signal appears at the o/p.
• When it is not activated, the o/p of the multivibrator is normally low. And when it is activated it will go higher for a short length of time based on the values of the resistor and capacitor.

Piezo Sensor

• When the o/p of the multivibrator touches the buzzer, then it generates the sound to specify the active action of the cell phone.
• The element of the piezoelectric may be driven by an oscillating electronic circuit and sounds are commonly used to denote that a button has been pushed are a ring, a click or a beep.

The circuit in the above can be used to detect both the incoming & outgoing calls, video transmission, and SMS even if the cell phone is kept in the mode of silent. The moment the bug notices Radio Freuency transmission signal from a triggered mobile phone, it starts generating a beep alarm and also the LED glows. The beep sound remains until the signal transmission ends.

Hidden Active Cell Phone Detector Project and It’s Working

The main concept of this project is to detect the existence of an activated cell phone from a distance of one and a half meters to avoid the use of cell phones in the hospitals, examination halls, etc.

This proposed system is very helpful in particular places like exam halls, offices, temples and theaters where uses of cell phones are not permitted to sense and control the use of cell phones.

This project is used to detect the active cell phone, when somebody is trying to make or receive a call, sending or receiving a message. A buzzer gives an alert in the occurrence of an active mobile phone in a distance of one and a half meters in the above-mentioned conditions.

In the proposed system, an RF signal detector using tuned LC circuits is designed for detecting signals in the GHz frequency band used in mobile phones as the transmission frequency of mobile phone ranges from 0.9 to 3 GHz.

A capacitor C and L are used to form the LC circuit to receive radio frequency signals from the cell phone. When the cell phone is triggered the radio frequency transmission signal is sensed by the detector and generates a beep sound and the LED will glow.

This is all about hidden active cell phone detector circuit and its working, the applications of this detector mainly include where the use of cell phone is forbidden like petrol pumps, gas station, historical places, religious places, court of laws, examination halls, spying, and unauthorized video transmission, military bases, hospitals, theatres, conferences, and embassies. We hope that you have got a better understanding of this concept. Furthermore, any doubt regarding this concept or electrical and electronic projects give your feedback in the comment section below. Here is a question for you, what are the advantages of a cell phone detector?