Simple Mobile Incoming Call Detector Circuit

The Simple Mobile Incoming Call Detector is a clever circuit designed to pick up incoming calls on a mobile phone and light up an LED.

This circuit is really useful in loud places where you might not hear the regular ringtone.

It works by detecting the radio frequency RF signal that a phone sends out when a call comes in.

To do this the circuit uses a specially tuned LC circuit, a transistor amplifier and a 555 timer, all working together to turn on the LED.

Also, it can easily run on a 6V battery which makes it super handy and efficient.

Circuit Working:

Parts List:

When a mobile phone gets a call it sends out radio frequency RF signals that create a small voltage across L1 inductor.

This inductor works together with a capacitor C3 to form a tuned circuit that can detect mobile signals.

The signal that comes from this setup is then boosted by a transistor Q1 which sends the stronger signal to a IC1 555 timer.

The timer is set up in a way that lets it turn on an LED for a short time showing that there is an incoming call.

The LED stays lit as long as the phone is receiving signals.

Diode D1 protects the circuit from any reverse voltage.

The resistors R1, R2 and R3 help with biasing and keeping the circuit working properly.

At the same time capacitors C1 and C2 help filter out noise and keep the circuit stable.

Formulas:

To design you own Simple Mobile Incoming Call Detector Circuit you need to use the following formulas:

LC Resonance Frequency:

f = 1 / (2 * π * √(L * C))

where,

• f is the resonant frequency
• L is the inductance of the coil
• C is the capacitance of the capacitor.

The circuit is tuned to a frequency typically around 900-1800 MHz which is common mobile signal bands.

Monostable Time Calculation (555 Timer):

T = 1.1 * R3 * C1

where,

• T is the output pulse duration
• R3 is the timing resistor
• C1 is the timing capacitor.

The output pulse width should be adjusted so that the LED remains on for a noticeable period when a call is detected.

How to Build:

To build a Simple Mobile Incoming Call Detector Circuit follow the below mentioned steps for connections and assembling:

• Gather all the components as mentioned in the above circuit diagram
• Connect pin 1 of IC1 to GND of the circuit.
• Connect pin 2 of IC1 between the junction of resistors R1 and R2.
• Connect pin 3 of IC1 between LED1 and diode D1 through capacitor C2
• Connect pin 4 and pin 8 of IC1 to positive supply of the circuit.
• Connect pin 6 and pin 7 of IC1.
• Connect capacitor C1 from pin 6 of IC1 and GND of the circuit.
• Connect resistor R3 from positive supply of the circuit o pin 7 of IC1.
• Connect collector of transistor Q1 to one end of resistor R1 and other end of resistor R1 connect between base of transistor Q1 and capacitor C3.
• Connect emitter of transistor Q1 to GND of the circuit
• Connect inductor L1 one end to capacitor C3 and other end of inductor L1 to GND of the circuit.
• Connect the positive supply of circuit to +6V battery and negative of 6V battery connect to GND of the circuit.

Conclusion:

The Simple Mobile Incoming Call Detector Circuit is an easy and efficient way to notice when someone is calling by using radio frequency signals.

This circuit is really helpful in situations where you can not hear your phone ringing.

By adjusting the LC circuit just right, you can make it more sensitive for improved results.

This project shows how simple electronic parts can come together to create handy and useful gadgets.

References:

Detect RF from cell phone