Mobile Phone Signal Detector - An Electronic Class Project for the Students
Here is another circuit from me of a Mobile Phone Signal Jammer (oops) Detector. It can sense the presence of an activated mobile within a distance of three to four meters and lights-up an LED (you can also attach a buzzer instead of LED). It can be a very useful device to locate anyone using a mobile in an examination hall or in a meeting hall where the use of mobile phone is strictly prohibited.
The circuit presented here can easily detect outgoing and incoming calls from a mobile. It can also sense SMS, Internet and any type of Data Transmission even if the mobile is in silent mode.
The concept of the circuit presented here is simple, that if it detects an ‘RF signal’ from any activated mobile, the Light Emitting Diode (LED) lights up and continues to flicker until the RF signals from the mobile phone stops.
The circuit presented here is wired around a very popular standard operational amplifier IC LM358 and a NPN Transistor BC548.
When the mobile phone becomes active (ie. when we make a call or receive a call / send SMS) it radiates Radio Frequency (RF) Signals that is passed around the nearby space. The capacitor 1uf 16V connected to the Antenna (Coil) and to the pin 2 of the IC is used here to detect the RF Signal from the Mobile Phone. Once the mobile phone is activated this capacitor (1uf 16V) gets charged up and passes the pulse to the input of the IC LM358’s Pin 2. This further triggers the transistor BC548 that amplifies the signal received from pin 1 of the IC and lights the LED. The preset (of 2.2M) used here is to set the sensitivity of the circuit. I have used a very crude copper wire coil here to test the circuit. But, the ideal coil parameter should be 18 turns of 24SWG coil on a regular ball-point pen should be good to achieve the maximum sensitivity and range.
This circuit works well for 2G networks, GPRS and network search (manual/automatic). I have tried testing it on 3G, WCDMA – it works sometime and sometime it skips.
The circuit is very easy and can be wired on a general purpose PCB. Please ensure to ground the circuit very securely for maximum signal strength and excellent results. It has been prepared as a school electronic project and cannot be used for professional purpose without modifications.
- IC LM358 (Operational Amplifier)
- BC548 Transistor
- LED (Light Emitting Diode)
- SPST Switch
- 2M Preset
- 1uf 16Volt Capacitor
- 100uf 16Volt Capacitor
- 1K Resistor
- 220K Resistor
- 100K Resistor
- Battery 4.5V (or use 3 Double A cells)
PRICE: Rs. 40/-