Security & Saftey

Luggage Security Alarm Project Circuit

During our train and bus journeys, we often carry valuable items in our luggage, and there’s always a concern about the security of our belongings. To mitigate this worry, we typically secure our luggage using traditional methods like chains and locks. However, despite these precautions, there’s still a lingering fear that someone might tamper with the lock or chain and steal our possessions. To address these concerns, we’ve devised a straightforward circuit based on NAND gates.

In this circuit, if someone attempts to tamper with your luggage, it will activate a warning alarm. This alarm system proves especially valuable during bus or train rides, even during nighttime travel, as it can also provide both auditory and visual alerts via a relay.

Additionally, this circuit can be adapted for home security purposes. By implementing it in your house, you can deter potential burglaries. If someone tries to breach your home’s security, a loop breakage triggers the alarm, generating a loud alert sound.

Luggage Security Alarm Circuit Diagram:

Luggage Security Alarm

Circuit Components:

  • IC
    • IC1(CD4011) – 1
  • Resistor
    • R1(1K) – 1
    • R2(4.7K) – 1
  • Capacitor
    • C1(.1uF) – 1
  • Miscellaneous
    • Relay – 1
    • T1(BC547) – 1
    • D1(1N4007) – 1

Luggage Security Alarm Circuit Description:

The CD4011 is the basic building block of this circuit, along with certain additional components such as resistors, capacitors, transistors, and relays, which are utilised to protect your valuables from thievery with the help of this simple circuit. When someone tries to unlock the lock, it emits a warning beep as the wire loop splits and an alarm is triggered.

To get familiar with the working, you should get aware with the NAND gate truth table which is shown below –

NAND Gate - Truth Table

When either or both of the input states of the NAND gate transition to a low state, the output becomes high. Conversely, if both inputs are in a high state, the output becomes low.

The CD4011, a Complementary Metal Oxide Semiconductor (CMOS) chip, is the commonly employed component in this context. It is available in a 14-pin Dual Inline Package (DIP) with a distinctive notch in one corner denoting pin 1. This chip contains four independent NAND gates within a single package. Each gate is a three-terminal device, featuring two input terminals and one output terminal. The IC’s operational voltage range spans from 5V to 16V, delivering approximately 10mA of current at 12V, which can be further adjusted by altering the power supply voltage.

The operation of these circuits is remarkably straightforward; the output depends on the voltage at pin 5. When power is supplied to pin 5 of the circuit, the voltage remains low as long as the loop remains intact. Consequently, pin 4 maintains a high voltage, which is connected to pin 1 and pin 2, both of which also remain in a high state.

As per the NAND gate truth table, when both inputs are high, the output is low. Therefore, pin 3 of gate 1 is in a low state, subsequently affecting pins 12 and 13, switching them to low as well. This, in turn, triggers pin 11 to go high, resulting in pins 8 and 9 turning high, while pin 10 remains at a low voltage due to the transistor connected to it via a resistor, preventing the activation of the alarm. This signifies the security of our luggage.

However, if someone attempts to tamper with your luggage and the loop breaks, pins 5 and 6 both transition to a high state, initiating the opposite sequence as explained earlier. This leads to pin 10 going into a high state, allowing the transistor to conduct and trigger the alarm. The alarm continues until the loop is re-engaged.

The battery voltage can vary between 6 and 15 volts, depending on the relay’s rating in your circuit. If you prefer not to use a relay, you can directly connect the buzzer. We incorporated a relay in our circuit to ensure compatibility if someone wanted to connect the alarm directly to AC power without causing any harm. Additionally, a diode is included in our circuit to safeguard against reverse voltage spikes, as it will short-circuit any reverse voltage spikes, preventing damage.


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