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Alarm Circuits
Alarms:  #'s       A - C       D - G       H - L       M - Q       R - T      
U - Z

 

Last Updated: October 18, 2017 05:04 AM

 

Circuits Designed by Dave Johnson, P.E.

Alarm Discriminator + Battery Monitor of the Electric Field Disturbance Monitor -  This schematic is the alarm discriminator plus the batterry monitor of my "Electric Field Disturbance Monitor".  The system can detect human and animal motion by the electric fields they disturb . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Alarm sounds when Power Cord is Unplugged -  Many medical devices, such a portable X-ray and ultrasound equipment, carry their own batteries.  However, the frantic pace of some hospital emergency rooms might cause the device to be shoved off into a corner without being plugged back into an AC power source to recharge their batteries.  So, I designed this circuit to emit an audible alarm whenever the device’s power cord was unplugged from the wall for a period of time . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2000

Alarm sounds when Water is Detected -  This simple circuit sounds a beeper when its electrodes detect water.  It is powered by a single 1.5v N cell.  A small 1.5v button battery will also work. . . Circuit by David Johnson P.E.-June, 2000

Another Very Loud piezo Alarm Beeper -  This is yet another beeper circuit that really draws attention.  It sweeps the drive frequency slightly to produce a very annoying sound.  It uses a transformer to increase the drive voltage across the piezo device to more than 200 volts peak to peak. . . Circuit by David A. Johnson P.E.-June, 2000

 
Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Alarm using discrete transistors -  The alarm may be used for a variety of applications, such as frost monitor, room temperature monitor, and so on.  In the quiescent state, the circuit draws a current of only a few microamperes, so that, in theory at least, a 9 V dry battery   (PP3, 6AM6, MN1604, 6LR61) should last for up to ten years.  Such a tiny current is not possible when ICs are used, and the circuit is therefore a discrete design.  Every four seconds a measuring bridge, __ Learning Electronics

Alarm using Your Own Voice -  This alarm plays your prerecorded voice message.  It is built around the readily available quartz clock.  Take the buzzer out of the quartz clock and connect its positive terminal to pin __ Electronics Projects for You

Alarm-Piezo Device Detects Motion -  Using a piezo device, this circuit will activate a beeper whenever the circuit is moved.  It could be used as an earthquake alarm. . . Circuit by Dave Johnson P.E.-July, 2006

Ambulance Siren -  This siren circuit simulates police, fire or other emergency sirens that produce an up and down wail. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

An Alarm Power Supply with Battery Back-up -  Power Supply Circuits:  This Power Supply is suitable for the Modular Burglar Alarm.  However, it has other applications.  It is designed to provide an output of 12-volts, with a current of up to 1-amp.  In the event of mains failure, the back-up battery takes over automatically.  When the mains is restored, the battery recharges. __ Designed by Ron J.

An Enhanced Shed / Garage Alarm -  Battery-Powered Alarm Circuits:  This is an enhanced version of the simple Garage/Shed Alarm.  The Entry and Exit delays have been increased to about 30-secondsand I've added a timed Siren cut-off and automatic Reset.  I've also replaced the LED with an entry Buzzer.  These enhancements mean that the new version will have a much wider application. __ Designed by Ron J.

An Expandable Multi-Zone Modular Burglar Alarm -  Multi-Zone Burglar Alarm Circuits:  This circuit features automatic Exit and Entry delays and a timed Bell Cut-off.  It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone.  By using the Expansion Modules, you can add as many zones as you require; some or all of which may be the inertia   (shock) sensor type. __ Designed by Ron J.

An Expandable SCR Based Burglar Alarm -  Multi-Zone Burglar Alarm Circuits:  This is a simple SCR based burglar alarm circuit.  Its features include automatic Exit and Entry delaystogether with a timed Bell Cut-off and Reset.  The basic alarm has a single zone.  This will be adequate in many situations.  Howeverthe modular design means that you can add as many zones as you like to the system.  Details of a Four-Zone expansion module are provided. __ Designed by Ron J.

An Expandable Transistor Based Burglar Alarm -  Multi-Zone Burglar Alarm Circuits:  This transistor based alarm features automatic Exit and Entry delaystogether with a timed Bell Cut-off and system Reset.  Along with the Exit/Entry zonethe basic alarm board has one Instant Zone.  This will be adequate in many situations.  Howeverthe modular design means that it's easy to add as many zones as you like to the system.  Details of a Four-Zone expansion module are provided. __ Designed by Ron J.

An introduction to acoustic thermometry -  04/21/11  EDN Technical Article: Use an ultrasonic transducer to measure air temperature in an olive jar. __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

AN062: TI-MAC & Z-Stack Modifications for using CC2591 RF Front End w/CC2430 (Rev. A) -  Glass Break Detector can be designed with 3 types of implementations in mind: Standalone, wireless connectivity and Fixed/Wired Connectivity.  The first two implementations are battery operated.  The functional block diagram of the glass break detector is divided into 3 sub-blocks: the sensing block, the processor and the communication interface blocks.  When implementing a basic standalone type of glass break detector, the processor and the communication interface are not needed __ Designed by Texas Instruments App Notes, 30-Sep-08

AN131An Introduction to Acoustic Thermometry -  Linear Technology AN131 __ Designed by Jim WilliamsApr 26th, 2011

Another Very Loud piezo Alarm Beeper -  This is yet another beeper circuit that really draws attention.  It sweeps the drive frequency slightly to produce a very annoying sound.  It uses a transformer to increase the drive voltage across the piezo device to more than 200 volts peak to peak. . . Circuit by David A. Johnson P.E.-June, 2000

Anti Theft Motorcycle Alarm -  Any number of normally open switches may be used.  Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand.  Use micro-switches to protect removable panels and the lids of panniers etc.  While at least one switch remains closed, the siren will sound.  About two minutes after the switches have been opened again, the alarm will reset. __ Designed by Ron J

Anti-Bag-Snatching Alarm -  Here is a simple alarm circuit to thwart snatching of your valuables while travelling.  The circuit kept in your bag or suitcase sounds a loud alarm, simulating a police horn, if __ Electronics Projects for You

Anti-Bag-Snatching Alarm -  Small, portable, anti-bag-snatching unit.  Also suitable for doors and windows control.

Anti-Carjack SystE - M -  Consider this: A criminal stops your car by force and you are left with no option but to surrender the car.  The criminal drives away your car, but about 60 seconds __ Electronics Projects for You

Anti-Hijack Alarm No.3 -  Automobile Alarm Circuits:  Like the first two Hijack Alarmsif a door is opened while the ignition is switched onthe circuit will trip.  And after a few minutes delaywhen the thief is at a safe distancethe Siren will sound.  But this time the engine does not go on to fail automatically.  Insteadit will continue to run until the thief turns off the ignition.  Then the engine will not re-start. __ Designed by Ron J

Anti-Petrol Theft Alarm -  Petrol/diesel theft of parked vehicles is quite common.  Presented here is an audio-visual anti-petrol theft alarm circuit that can help prevent this crime.  The circuit consists of transmitter and receiver sections. __ Electronics Projects for You

Anti-Sleep Alarm -  Most of the accidents on highways during night occur due to drivers’ poor vision caused by the continuous exposure of their eyes to the bright light from the headlamps of approaching __ Electronics Projects for You

Antisleep Alarm for Students -  This circuit saves both time and electricity for students.  It helps to prevent them from dozing off while studying, by sounding a beep at a fixed time interval, say, 30 minutes. __ Electronics Projects for You

Anti-Theft Alarm -  You can use this circuit to thwart burglary.  It sounds an alarm when someone tries to intrude into your home or office by hitting, pushing or knocking the door.  The sensor __ Electronics Projects for You

Anti-Theft Alarm for Vehicles -  This simple and inexpensive anti-theft circuit for vehicles sounds an alarm simulating a police siren whenever someone attempts theft of your vehicle.  The alarm sounds continuously for a few seconds even __ Electronics Projects for You

Anti-theft Car Alarm -  Here is a simple Anti theft car alarm device for your Car.  It generates a loud alarm when there is an attempt of theft.  When the intruder opens the door, the circuit senses the attempt of theft and after 2 minutes, the alarm will be activated.  The time delay is provided to help the user to leave the car after arming with the __ Designed by D Mohankumar

Anti-Theft Security for Car Audio -  This small circuit, based on popular CMOS NAND chip CD4093, can be effectively used for protecting your expensive car audio system against theft.  When 12V DC from the car battery is applied to the gadget   (as indicated by
LED1) through switch S1, the circuit goes into standby mode.  LED inside optocoupler IC1 is lit as its cathode terminal is grounded via the car audio   (amplifier) body.  As a result, the output at pin 3 of gate N1 goes low and disables the rest of the circuit. __ Learning Electronics

Appliance Unplugged Alarm -  I received a call from an administrator at a large prison.  He told me that he was having problems with inmates who keep unplugging refrigerators, vending machines and microwave ovens in a commons area.  He wanted a battery-powered device, which could be mounted to the outside of the power cord of an appliance. . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2010

Aqua Alarm -  Here is another interesting hobby circuit built around the popular and inexpensive 555 IC.  It is nothing but a water sensor, which you can be configured as a rain alarm, water tank overflow alarm, aquarium water leak indicator, etc.  It can be powered from any 6VDC supply.  Initially, when DC supply is fed to the circuit the Red __ Designed by T.K. Hareendran

Arduino Flame Sensor Interface -  Build fire alarm or fire detector using Flame sensor and Arduino board, the sensor basically detects IR   (Infra Red) light wavelength between 760 nm – 1100 nm   (nano meter) that is emitted from fire flame.  Most of the flame sensors came with YG1006 sensor which is a high speed and high sensitive NPN silicon photo transistor.  It is covered with black epoxy, since the sensor is sensitive to infrared radiation

Arduino Panic Alarm -  Here is the circuit of an Arduino-based Panic Alarm! The wiring is very simple so that even a novice can construct this interesting circuit without any difficulty.  Arduino is a family of microcontrollers   (tiny computers) and a software creation environment   (Arduino IDE) that makes it easy for you to create programs   (called __ Designed by T.K. Hareendran

Audio Security Monitor -  A remote listening circuit.  The area to be monitored is connected via a cable and allows remote audio listening. __ Designed by Andy Collison

Aurora Alarm: Automated Detection System for the Northern Lights -  To increase one's chances of seeing the northern lights, the uncertainties of existing aurora prediction methods can be bypassed by sensing the light from the aurora directly.  The Aurora Alarm is a device which accomplishes this objective through the use of a narrowband optical filter, a photomultiplier tube detector, and a flexible microprocessor system for high voltage control and alarm determination. __ Designed by Mark A. Haun

Auto Snooze For Digital Alarm Clocks

Auto Snooze for Digital Alarm Clocks 2 -  Alarm clocks are made to wake you up.  However, it is quite bothersome to hear the alarm continuously until you get up and put it off.  Also, you might fall asleep __ Electronics Projects for You

Automated Alarm Circuits -  Two alarm circuits are presented here.  One produces bird-chirping sound and the other British police siren tone.  Fig.1 shows the circuit of the bird-chirping-sound alarm unit along with the circuit of the __ Electronics Projects for You

Automatic Heat Detector -  This circuit uses a complementary pair comprising npn metallic transistor T1   (BC109) and pnp germanium transistor T2   (AC188) to detect heat   (due to outbreak of fire, etc) in the vicinity and __ Electronics Projects for You

Automatic Intruder Alarm -  This is a simple single-zone burglar alarm circuit.  Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off.  It's designed to be used with the usual types of normally-closed input devices such asmagnetic reed contactsmicro switchesfoil tapeand PIRs.  But it can be Easily Modified to accept normally-open triggering devicessuch as pressure mats. __ Designed by Ron J

Automatic Night Lamp with Morning Alarm -  This circuit automatically turns on a night lamp when bedroom light is switched off.  The lamp remains ‘on’ until the light sensor senses daylight in the morning.  A super-bright white LED __ Electronics Projects for You

Automatic Night Lamp with Morning Alarm -  This circuit project automatically turns on a night lamp when bedroom light is switched off.  The lamp remains ON until the light sensor senses daylight in the morning.  A super-bright white LED is used as the night lamp.  It gives bright and cool light in the room.  When the sensor detects the daylight in the morning, a melodious __ Designed by Popescu Marian

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Alarms:  #'s       A - C       D - G       H - L       M -Q       R - T       U - Z

 


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