Mobile incoming call indicator
Description.
This
circuit can be used to escape from the nuisance of mobile phone rings when you
are at home. This circuit will give a visual indication if placed near a mobile
phone even if the ringer is deactivated.
When a
call is coming to the mobile phone, the transmitter inside it becomes
activated. The frequency of the transmitter is around 900MHz.The coil
L1 picks up these oscillations by induction and feds it to the base of Q1. This
makes the transistor Q1 activated. Since the Collector of Q1 is connected to
the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at its
output pin (pin 3) to blink. The blinking of the LED is the indication of
incoming call.
Circuit diagram with Parts list.
Notes.
§ The
coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm
dia plastic former. Or you can purchase a 10 uH coil from shop if available.
§ The
circuit can be powered from a 6V battery.
§ Assemble
the circuit on a good quality PCB.
§ C1 &
C3 are to be polyester capacitors.
§ The
electrolytic capacitor C2 must be rated 10V.
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