23-06-2012, 12:36 PM
MOBILE PHONE SIGNAL JAMMER WITH PRESCHEDULED
TIME DURATION
MOBILE PHONE SIGNAL JAMMER .pdf (Size: 1.03 MB / Downloads: 333)
INTRODUCTION
Cell phones are everywhere these days. It’s great to be able to call anyone at anytime.
Unfortunately, restaurants, movie theaters, concerts, shopping malls and churches all suffer from
the spread of cell phones because not all cell-phone users know when to stop talking While most
of us just grumble and move on, some people are actually going to extremes to retaliate.
Disrupting a cell phone is the same as jamming any other type of radio communication. A
cell phone works by communicating with its service network through a cell tower or base station.
Cell towers divide a city into small areas, or cells. As a cell-phone user drives down the street,
the signal is handed from tower to tower A jamming device transmits on the same radio
frequencies as the cell phone, disrupting the communication between the phone and the cellphone
base station in the tower Jamming devices overpower the cell phone by transmitting a
signal on the same frequency and at a high enough power that the two signals collide and cancel
each other out.
AIM OF THE PROJECT:
Here our main intention is to block the signals of mobile phone using mobile phone
signal jammer for prescheduled time duration using real time clock controlled by
microcontroller. Switches are used to set the time for start and stop of jammer.
POWER SUPPLY:
The input to the circuit is applied from the regulated power supply. The a.c. input i.e.,
230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The
output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage,
the output voltage from the rectifier is fed to a filter to remove any a.c components present even
after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc
voltage.
Transformer:
Usually, DC voltages are required to operate various electronic equipment and these
voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input
available at the mains supply i.e., 230V is to be brought down to the required voltage level. This
is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a
required level.
Filter:
Capacitive filter is used in this project. It removes the ripples from the output of rectifier
and smoothens the D.C. Output received from this filter is constant until the mains voltage and
load is maintained constant. However, if either of the two is varied, D.C. voltage received at this
point changes. Therefore a regulator is applied at the output stage.
Fig: 2.5 Capacitive Filter
2.2.4 Voltage