The main scope of project is to sense the presence of an activated mobile phone from a distance of one-and-a-half meters to prevent the use of same in the examination halls. In this project an RF detector using tuned LC circuits is formed 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. So, a tuned circuit detecting a gigahertz signal is required for detecting an active cell phone. Here an operational amplifier is used to receive very low current signal which is fed to a current to voltage converter and the output of the same is given to the transistor. The output from the transistor is connected to a 555 Timer for triggering in monostable mode. A capacitor is used to form a part of the LC circuit as C while the lead of the same forms the L to receive RF signals from the mobile phone. When the mobile phone is activated the RF transmission signal is detected by the detector and starts sounding a beep alarm and the LED blinks.
For complete information about this project, visit http://www.edgefxkits.com/hidden-active-cell-phone-detector