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Security and Alarm

Password Lock Circuit Using IC 4017

Last Updated on January 5, 2022 by Swagatam 27 Comments

4017 based password lock circuit

In this post I will show how to construct a general purpose password based electronic lock circuit without any involvement of microcontroller. You can use this circuit for numerous applications where a basic level of security is required for turning a circuit ON. The proposed project is built using an IC 4017 and the circuit […]

Filed Under: Security and Alarm Tagged With: 4017, Lock, Password

3 Accurate Infrared Intruder Alarm Circuits using Photodiodes

Last Updated on January 19, 2025 by Swagatam 31 Comments

IR transmitter

In this post I have explained 3 simple yet accurate infrared intruder alarm circuits using an infrared transmitter and an infrared receiver module. The transmitter and the receiver photo diodes used in the two modules are aligned in line at a distance of around 2 meters within the restricted area. When a burglar tries to […]

Filed Under: Security and Alarm Tagged With: Accurate, Alarm, Circuits, Infrared, Intruder, Photodiodes

7 Interesting IC 555 Siren and Alarm Circuits

Last Updated on December 26, 2024 by Swagatam 45 Comments

whooper siren compressed

In this post I have explained how to use IC 555 to create 7 interesting siren and alarm sound effect generator circuits. The versatile astable multivbrator configuration of IC 555 allows us to implement it for making various types of sirens and alarm circuits. This becomes possible because an astable is basically a waveform generator, […]

Filed Under: Security and Alarm Tagged With: 555, Alarm, Circuits, Interesting, Siren

Simple Anti-Theft Alarm Circuit to Protect Valuable Items

Last Updated on May 24, 2022 by Swagatam 9 Comments

movement alarm circuit compressed

This easy yet useful security alarm circuit is designed to get triggered in response to even a brief movement of the unit, causing a loud alarm sound to set off. The circuit could be attached or installed on any desired gadget or asset which needs to be protected from theft. As soon as the gadget […]

Filed Under: Security and Alarm Tagged With: Alarm, Anti, Protect, Simple, Theft, Valuable

How Laser Microphones or Laser Bugs Work

Last Updated on November 25, 2023 by Swagatam 2 Comments

laser mic block diagram compressed

A laser microphone is a security monitoring gadget in which a laser beam is used for detecting audio vibrations across faraway targets, which are normally walls or glass of homes or offices. These devices could be applied for eavesdropping with virtually no chance of getting identified or cover getting blown. Laser eavesdropping gadgets, it is […]

Filed Under: Security and Alarm Tagged With: Bugs, Laser, Microphones, Work

Touch Alarm Circuit

Last Updated on July 23, 2023 by Swagatam 2 Comments

block diagram of hum alarm

The touch alarm circuit senses the mains hum signal from an intruder’s body and raises the alarm sound. This happens whenever an intruder touches a potential element set as the sensor, such as the door knob, or any object that needs to be protected. If the circuit is linked with the door knob, the circuit […]

Filed Under: Security and Alarm Tagged With: Alarm, Touch

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