Mobile Phone Detector Circuit Using LM358

I’ll walk you through a basic mobile phone detector project in this article that makes use of an inexpensive LM358 op-amp. From a distance of four to five metres, this mobile phone detector can determine whether a cell phone is nearby. Thus, it can be useful at meetings or assessment lobby areas where cell phones are prohibited.

Whether a mobile phone is kept in silent mode or not, the mobile phone detector circuit can detect incoming and outgoing calls, SMS, internet, and video transmissions. Its LED starts to flicker as soon as it detects an RF signal from a mobile phone that has been turned on, and it does so until the signal stops.


Mobile Phone Detector Circuit Diagram

Circuit Schematic

Mobile Phone Detector Circuit Diagram


  • LM358 Op-Amp
  • BC548 NPN Transistor
  • 100uF/16V Electrolytic Capacitor
  • 1uF/16V Electrolytic Capacitor
  • Resistors (1KΩ, 220KΩ, 100KΩ)
  • 100K Preset
  • LED
  • Antenna
  • Connecting Wires
  • 3.7V Battery

Circuit Connection

Pins 8 and 4 of the LM358 op-amp are initially directly connected to ground and Vcc, respectively, in this cell phone detector.

Pin 3 is connected to the VCC via a 220KΩ resistor and to ground via a 100uF electrolytic capacitor. Pin 2 and Pin 3 are further connected by means of a 1 uF electrolytic capacitor.

The right terminal of a 100KΩ preset is connected to pin 1, the left terminal to pin 2, and the middle terminal to pin 1 of the op-amp integrated circuit.

Pin 1 of the IC is connected to the base terminal of an NPN transistor. An additional emitter terminal and collector are linked to Vcc via the LED’s cathode and a 1KΩ resistor, respectively. The LED’s anode terminal is attached to the ground directly.

Pin 2 is connected to ground via a 100KΩ resistor in addition to two parallel capacitors. Additionally, pin 2 of the IC is connected to an antenna.

The circuit is connected to a 5V power supply in order to distribute the necessary power.

Working Principle of Mobile Phone Detector Circuit

An RF signal is released by a mobile phone when it is turned on, and this signal travels through nearby space. Electromagnetic radiofrequency radiation from the cell phone is present in the signal.

The circuit uses capacitor C1 to differentiate the RF signal from the cell phone. When the mobile phone emits an RF signal, C1 captures it and transfers it to IC’s contributions. The LED’s blinking indicates this. The potentiometer VR1 is used to adjust the circuit’s scope. The signal received at pin 1 of the IC is amplified by transistor T1.

This circuit for detecting mobile phones is suitable for GPRS, 2G, and network searches. It has trouble distinguishing between 3G, WCDMA, and HSDPA networks.

Application of Mobile Phone Detector

There are several uses for a dual-operational amplifier integrated circuit (LM358) mobile phone detector circuit:

Security: It can be used to identify instances of unapproved mobile phone use in places that are off-limits, including exam rooms, libraries, or secure buildings.

Silent Zones: Establish them in places where cell phone use is prohibited, such as meeting rooms, theatres, and hospitals, to guarantee adherence to no-phone rules.

Prisons and Correctional Facilities: Install a detector circuit to stop unauthorised usage of cell phones on prison property.

Automobiles: Use the circuit in your automobile to establish a zone off-limits to cell phones, which will deter distracted driving.

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