新闻稿 - 1 ， 2017 10:44

Detector Circuit Based on Mobile Phone

Circuit Diagram

Mobile Phone Detector – Hobby Project – Circuit Diagram

The circuit can be basically divided into two parts,

RF Signal Detector
Sound Generator

Making:

Cell Phone Detector - Hobby Project - Breadboard

Mobile Phone Detector - PCB Model Mobile Phone Detector Circuit

Components Required

Battery Connector
555 Timer IC
ON-OFF Switch
CA3130 OP-AMP
0.01μF Capacitor
BC548 Transistor
Buzzer
Battery Connector
9V Battery
2x 1KΩ Resistors
PCB
2x 2.2MΩ Resistors
2x 100KΩ Resistors
15KΩ Resistor
2x LEDs
47pF Capacitor
22μF Capacitor
0.1μF Capacitor
22pF Capacitor
4.7μF Capacitor

RF Signal Detector:
The first half of the circuit makes RF signal detecting section. Capacitor C7 (0.22μF) is the main component which will sense high frequency RF signals. CA3130 op-amp is wired as an inverting amplifier with high gain. It provides very high input impedance and high speed performance to amplify RF signals detected by the capacitor C7. You can see that one terminal of the capacitor C7 is biased with two resistors R6 and R7. Capacitor C6 (100μF) will prevent any fluctuations in the bias voltage. Capacitors C9 and C8 (22pF) are used to filter input signals. Thus in normal conditions the opamp will be in balanced state.
So when high frequency mobile signals are present in the vicinity of this circuit, the capacitor C7 will get energized and distorts the balance of the opamp. This operates the Q1 (BC548) transistor wired as a switch. Thus the LED D1 is operated and signals are coupled to the next section for generating sound indication.

BC548 Datasheet

Sound Generator:

Sound generator is composed of a 555 timer wired as monostable multivirator and a buzzer. Output signals from RF Signal Detection section will trigger the 555 timer. Time period of each tone can be adjusted by varying the capacitor C1 and resistor R2.

Notice:

When the circuit is switched on, LED D2 will indicate that it is ON. Now you can place a mobile near this circuit and try making a call or sending an SMS. You can see that the buzzer is producing sound and LED D1 is indicating detection of signals.