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Car Alarm and Immobilizer

This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize... [read]

Garage - Shed Alarm

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays. It's designed to be used with the usual types of... [read]

Frost Alarm

A simple thermistor triggered cold switch with adjustable threshold.... [read]

5 Zone Alarm System

This is a complete alarm system with 5 independent zones suitable for a small office or home environment.... [read]

Single Zone CMOS Alarm

This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It has provision for normally open and normally closed switches and... [read]

Fuse Monitor - Alarm

This device monitors a fuses in your circuits. LED turns on when fuse is blown.... [read]

Car Alarm Arming Horn Beep Canceller

This circuit serves to silence the arming beep yet maintain the alarm by introducing a small delay into the signal. It sits between the alarm and horn relay.... [read]

Power supply failure alarm

Most of the power supply failure indicator circuits need a separate power supply for themselves. But the alarm circuit presented here needs no additional supply... [read]

Theft preventer alarm

This circuit utilizing a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms... [read]

Rain Alarm

This circuit gives out an alarm when its sensor is wetted by water. A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting... [read]

Water Level Indicator with alarm

This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full. The circuit uses the widely... [read]

4 in 1 Burglar Alarm

In this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2.... [read]

Car anti theft wireless alarm

This FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system.... [read]

Fire Alarm

This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and... [read]

DayLight Alarm

The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable... [read]

Timed Burglar Alarm

This is a simple but effective alarm circuit which can reset its self after a time that you select. it has normally open and normally closed triggers which... [read]

Electronic Keypad

Secure any electronic device using this electronic keypad. Circuit is relatively simple and it's built with 4081 CMOS quad 2 input "AND" gate... [read]

Audio Line Driver

This preamplifier has a low output impedance, and is designed to drive long cables, allowing you to listen to a remote music source without having to buy expensive... [read]

Melody generator for greeting cards

This tiny circuit comprising of a single 3 terminal IC UM66 can be built small enough to be placed inside a greeting card and operated off a single 3V flat... [read]

Cut Phone Line Detector

When the circuit detects that a phone line has been cut, it activates a MOSFET which can be used to drive a relay, motor, etc. It can also be connected to... [read]

Simple optical switch

The 555 is proved to be the most versatile and ubiquitous IC all over the world.This is a possible use: simple inverting schmitt trigger.... [read]

8 Channel software controlled fanbus with PWM

This article is about a software controlled, parallel port-interfacing 8-channel Pulse-Width-Modulated fan controller.... [read]

Electromagnetic Field Detector

This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer.... [read]

AC Current Monitor

This circuit was designed on request, to remotely monitor when a couple of electric heaters have been left on.... [read]