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Security and Alarm

LPG Gas Leakage Detector Alarm Circuit

Last Updated on September 24, 2026 by Swagatam 7 Comments

MQ 6

Are you feeling vulnerable or suspecting a possible LPG gas leakage in your house? Then may be this gas leakage alarm circuit might help you. Written by: Sai Srinivas The Concept This circuit is a simple solution for detecting LPG gas leakage in households which causes severe physical and monetary losses if left unattended for […]

Filed Under: Security and Alarm Tagged With: Alarm, Detector, Leakage, LPG

A Homemade Fence Charger, Energizer Circuit

Last Updated on July 21, 2026 by Swagatam 158 Comments

AC fence charger circuit

The electric fence charger circuit presented here is basically a high voltage pulse generator. The super high voltage is derived from a commonly used automobile ignition coil. An astable multivibrator is used to generate the required frequency to drive the ignition coil. Another astable is used to control the pulses supplied to the fence. Audio/Video […]

Filed Under: Security and Alarm Tagged With: Charger, Energizer, Fence, Homemade

Monitoring 220V AC Load Current using Current Transformer [Circuit Diagram]

Last Updated on June 25, 2026 by Swagatam 36 Comments

current sensing transformer

In this post I have explained a circuit which can be used for monitoring or controlling AC 220V load current by sensing the load current through a contactless current transformer. Figure 1 below depicts a circuit diagram designed for a non contact load current sensing through a current transformer, which seemed to work well. It is […]

Filed Under: Security and Alarm Tagged With: 220V, AC, Current, Load, Monitoring, Transformer

Fence Charger Animal Contact Detector Circuit with Audible Buzzer

Last Updated on June 2, 2026 by Swagatam Leave a Comment

In one of my electric fence charger articles, one reader asked me something interesting. He wanted to know whether a buzzer could be made to sound whenever an animal touches the fence. At first I was thinking about a current sensing method because that looks like the obvious way. But after looking at how electric […]

Filed Under: Security and Alarm, Sensors and Detectors Tagged With: Animal, Audible, Charger, Contact, Detector, Fence

Mains High Low Voltage Protection Circuit with Delay Monitor

Last Updated on May 25, 2026 by Swagatam 167 Comments

opamp2BV

In this post I have explained an upgraded version of my previous mains 220V/120V high-low voltage cut off protection circuit which now includes a delayed restoration of power for the load with 3 LED power status indicators. The idea was requested by one of the dedicated members of this website. Circuit Objectives and Requirements Main […]

Filed Under: Security and Alarm Tagged With: Delay, High, Mains, Monitor, Protection, Voltage

Simple Car Shock Alarm Circuit

Last Updated on May 16, 2026 by Swagatam 6 Comments

CARSHOCKALARMCIRCUIT

A simple car shock alarm circuit I have I have explained in this article can eb effectively used to alarm the owner each time the car comes across some kind of vibrational intrusion ether from a potential theft of simply a damaging hit from  an external source. Introduction Today most of the cars are equipped […]

Filed Under: Automobile Electronics, Security and Alarm Tagged With: Alarm, Shock, Simple

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