1 Mobile Phone Detector

This project is a simple mobile cellphone detector circuit. As the phone receives or sends massage or call, it sends off signal. The emitted signal will be detected by the circuit and will cause the LED to light up and the buzzer to sound. You can use this circuit as decoration to your cellphone or use this as a detector to unauthorized use of cellphone in prohibited area. Any cellphone activities like sending or receiving SMS, sending videos or any form of data transmission can be detected by this simple circuit. R5 and C7 set the duration of the buzz and ON time of the LED for 1 sec (you can modify it using the 555 timer calculator in monostable mode). Click diagram to enlarge.
phone detector circuit
Part List:
R1, R2 - 2.2 Mega ohms 1/4W
R3, R6 - 1.2 kilo ohms 1/4W
R4, R5 - 10 kilo ohms 1/4W
R7 - 100 kilo ohms 1/4W
C1, C2 - 22pF ceramic capacitor
C3, C7 - 47uF electrolytic capacitor rated 16V
C4 - 220nF
C5 - 33pF ceramic capacitor
C6 - 4.7uF electrolytic capacitor rated 16V
C8 - 100nF
ANT -  just a piece of conductor less than 1ft
Q1 - 2N2222 or similar NPN transistor
LED - red led (see LED pinout in case you forgot)
Buz - 12V buzzer
555 - LM555 or similar timer IC
IC - CA3130 or similar
Bat - 9V to 12V battery

Parts pinout: click diagram to enlarge
CA3130 pins
555 pinout
2N2222 pinout


  1. what frequency of cell phone is detected by this circut?