- This circuit can be used to escape from the nuissance of obile 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.
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.
