Op-Amp Mobile Phone Detector Board

Introduction

The Mobile Phone Detector board is a simple sensor that can detect a mobile phone that is present within a range of 1.5 meters. This sensor board utilizes the functionalities of the mobile phone where it detects the phone once a GPRS application is used, when the phone either receives or sends SMS, or when it is on an incoming or outgoing call.

The circuit detects an active RF signal from a mobile phone under the conditions stated above and switches an LED on to indicate. The LED starts blinking when there is an incoming call and will only stop when the incoming call stops.

Components

· 1 LM358 Dual Op-Amp IC

· 1K Resistor

· 100K Resistor

· 220K Resistor

· 2.2M Potentiometer

· 1Uf, 16V Electrolytic Capacitor

· 100Uf, 16V Electrolytic Capacitor

· BC548 NPN Transistor

· 5mm Red LED

· 15cm Single strand wire antenna

· 4.5V Battery Power Supply

The Circuit Diagram

The circuit is made up of an LM358 dual Op-Amp IC with its supporting active and passive components. It has an active LED that is deployed as an indicator when the cell phone is present. The Op-Amp in this circuit is integrated as a frequency detector and the output is connected to an LED USING BC547 or BC548 NPN transistor. This circuit can be built in a breadboard but for me, I like designing it as a complete board and sharing it with some manufacturers for complete board fabrication. Below is the circuit designed using KiCAD EDA.

An active mobile phone radiates RF signals in the form of electromagnetic radiation. When mobile phones radiate this energy as RF signals, the capacitor C1 absorbs it and delivers it to the input of LM358 Op-Amp. The LM358 IC output is connected to the LED through the BC548 transistor which is turned ON. Here you will see the flashing of the LED. The connected potentiometer RV1 is suitable for adjustment of the circuit sensitivity range.

PCB Gerber Files and Online Ordering

If you don’t like assembling the project using the breadboard, then you can convert it to PCB. The PCB board is designed in the KiCAD EDA tool. The PCB layout appears to be something like the one attached below.

This is a complete PCB layout with all the finishing done in standard and ready for manufacturing. The track sizes used are 0.250mm in size. All the components have been added with the 3D footprints for rendering purposes. The board size is 31.1150 by 13.5896 mm.

The 3D Output and Rendering

Below is the three-dimensional output of our design.

This device is powered by a battery of 4.5V connected through the input pin on the board. The Garber files from KiCAD are nicely downloaded and shared with the manufacturers for fabrication.

To order for fabrication, visit PCBWay’s official website, click on the instant quote page, place your order following the relevant easy steps, pay for the order, and wait for the complete product to be delivered to your shipping address within seven days.

For the order to be complete, ensure that you upload your Gerber files and relevant BOM files here.