Simple Wire Loop Security Alarm Circuit

A simple wire loop alarm is a small security circuit that uses a thin wire as a sensor loop and if someone cuts or opens the loop, the buzzer sounds.

Also, it works on 9V battery, needs few parts, is cheap and easy to make.

Circuit Working:

Parts List:

Components	Values	Qty
Resistors	4.7M 1/4 watt	1
	100k 1/4 watt	1
Capacitor	0.1µF	1
Semiconductors	N-MOSFET 2N7000	1
	Buzzer 9V	1
	Wire loop sensor thin insulated wire	1
	Battery 9V PP3	1

This is simple wire loop alarm circuit using MOSFET 2N7000, buzzer and few parts.

Normally, the wire loop and the 100k resistor R2 connect the gate of Q1 to ground and if someone cuts the wire loop, Q1 turns ON and the buzzer sounds.

Then circuit uses very less current in standby so battery lasts long and the whole circuit runs on 9V PP3 battery.

How to Build:

To build a Simple Wire Loop Security Alarm Circuit follow the connections steps below:

• First, take all parts as in circuit diagram.

Battery connection:

• Then battery 9V positive goes to R1 and buzzer and battery negative goes to ground.

Resistor and capacitor connection:

• After that, R1 goes from battery positive to MOSFET gate.
• Now R2 goes between wire loop and gate and then C1 goes between gate and ground.

Wire loop connection:

• Further, wire loop goes between R2 and ground.

MOSFET connection:

• Now MOSFET gate connects with R1, R2 and C1, source pin goes to ground and drain pin goes to buzzer and battery positive.

Buzzer connection:

• Finally, buzzer one side connects to battery positive and other side to MOSFET drain.

Conclusion:

To conclude, this Simple Wire Loop Security Alarm Circuit is useful for security, it can protect doors, windows or valuable things.

We can easily hide the loop wire and the buzzer sounds immediately if someone cuts or opens the loop; therefore, beginners can build this circuit easily.