Simple wire loop alarm is small security circuit.
It uses thin wire as sensor loop.
If loop is cut or opened the buzzer will sound.
It works on 9V battery, needs few parts, is cheap and easy to make.
Circuit Working:
Parts List:
| Component | Specification | 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 gate of Q1 goes to ground through 100k resistor R2 and wire loop.
If wire loop is cut, Q1 turns ON and buzzer makes sound.
Circuit uses very less current in standby so battery lasts long.
It runs on 9V PP3 battery.
How to Build:
To build a Simple Wire Loop Security Alarm Circuit follow the connections steps below:
- Take all parts as in circuit diagram.
Battery connection:
- Battery 9V positive goes to R1 and buzzer and battery negative goes to ground.
Resistor and capacitor connection:
- R1 goes from battery positive to MOSFET gate.
- R2 goes between wire loop and gate.
- C1 goes between gate and ground.
Wire loop connection:
- Wire loop goes between R2 and ground.
MOSFET connection:
- MOSFET gate connects with R1, R2 and C1.
- MOSFET source goes to ground.
- MOSFET drain goes to buzzer and battery positive.
Buzzer connection:
- Buzzer one side connects to battery positive and other side to MOSFET drain.
Conclusion:
This Simple Wire Loop Security Alarm Circuit is useful for security.
It can protect doors, windows or valuable things.
Loop wire can be hidden easily.
If someone cuts or opens the loop the buzzer sounds at once.
The circuit is easy for beginners to build.
References:
How can I make an alarm circuit which senses both cutting and shorting the wire?