Mobile Incoming Call Detector Circuit

Mobile Incoming Call Detector Circuit is a smart project, which detect incoming call and make LED light up.

Circuit is good for noisy places where ringtone is hard to hear and can catch RF signal from phone when call comes.

In addition, the circuit uses LC circuit, transistor, 555 timer to turn ON LED and also circuit runs on 6V battery and is useful and save power.

Circuit Working:

Parts List:

Components	Values	Quantity
Resistors (All resistors are 1/4 watt unless specified)	100k, 3.9k, 1M	1 each
Capacitors	Polyester 100nF	2
	Electrolytic 220µF 25V	1
Semiconductors	IC 555 Timer	1
	Transistor BC547	1
	Diode 1N5819	1
	LED any 5mm, 20mA	1
	Inductor 150 turns of 36 SWG enameled copper wire on a 5mm diameter plastic former	1
	Battery 6V	1

When phone gets call it sends RF signal and then signal makes small voltage on inductor L1, then L1 and C3 make tuned circuit to catch mobile signal.

After that, signal goes to transistor Q1 and make it stronger and strong signal then go to 555 timer IC1, thus timer turn ON LED for short time to show incoming call.

Furthermore, LED stay ON while phone get signal, diode D1 protect circuit from wrong voltage, R1, R2 and R3 set right current and then C1 and C2 remove noise and keep circuit steady.

Formulas:

To make our own Simple Mobile Incoming Call Detector we can use these formulas:

LC Resonance Frequency:

f = 1 / (2 * π * √(L * C))

where,

• f is the frequency
• L is the coil inductance
• C is the capacitor value

Set circuit to around 900 to 1800 MHz which is mobile signal range.

555 Timer Pulse Time:

T = 1.1 * R3 * C1

where,

• T is how long LED stays ON
• R3 is the resistor
• C1 is the capacitor

Hence, make T long enough so LED is easy to see when call comes.

How to Build:

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

• First, collect all parts as shown in circuit diagram.
• Next, connect pin 1 of IC1 to GND.
• Then connect pin 2 of IC1 between R1 and R2.
• Now, connect pin 3 of IC1 between LED1 and D1 through C2.
• Also, connect pin 4 and pin 8 of IC1 to +6V supply.
• Further, connect pin 6 and pin 7 together and then connect C1 from pin 6 to GND.
• Next, connect R3 from +6V to pin 7.
• Then collector of Q1 goes to one side of R1, other side of R1 goes to base of Q1 and C3 and emitter of Q1 goes to GND.
• Also, one end of L1 goes to C3 and other end goes to GND.
• Finally, connect +6V battery to positive side and negative to GND.

Conclusion:

To conclude, this Mobile Incoming Call Detector Circuit helps see when phone gets call using RF signal; also it is very helpful when we cant hear the ringtone.

So tuning the LC circuit increases its sensitivity, and therefore this circuit uses simple components and serves as a very useful device.