Cellular phone detector circuit
This cellular phone detector circuit can sense the presence of an activated mobile cell phone from a distance of one and-a-half meters.
If a RF signal is detected the circuit will inform you using a sound alarm (beep sound ) and a blinking LED .
This cellular phone detector circuit can detect any activity of a mobile phone: incoming or outgoing SMS , video transmission or voice transmission .
In this type of circuit (that use high frequency 0.9-3Ghz) you can not use an LC circuit for frequency tuning .
The circuit uses a 0.22μF disk capacitor (C3) to according the RF circuit to ensure the capability of the circuit to capture the mobile phone signal .
The C3 capacitor must have leads length of 18 mm with 8 mm spacing between leads to obtain the desired frequency . This small disk capacitor acts as a small gigahertz loop antenna to collect the RF signals .
The CA3130 operational amplifier IC is used as a current to voltage converter .