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Alarm Circuits
Alarms:  #'s       A - C       D - G       H - L       M - Q       R - T      
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Last Updated: December 07, 2017 02:03 PM

 

Circuits Designed by Dave Johnson, P.E.

Bad Light Bulb Indicator  -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor . . . Circuit by David Johnson P.E.-December 17, 2006

Basement Doorbell Beeper  -  if you can't hear your doorbell when you are in your basement try this circuit.  This circuit takes advantage of the 24vac power source located near the furnace.  Using a simple current transformer technique, the circuit sounds a beeper whenever the . . . Circuit by David Johnson P.E.-June 04, 2000

Basement Remote Doorbell  -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by David A. Johnson P.E.-July 11, 2006

Battery-Powered Freezer Alarm  -  A typical freezer can contain hundreds of dollars with of food.  If the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by David Johnson P.E.-July 20, 2006

Broken_Fence_Alarm  -  It was deer hunting season and cattle rancher was fed up with hunters cutting his barbed wire fence, to gain entrance onto his property.  The rancher want to be alerted when the barbed wire was cut.  The circuits below is placed inside a small plastic box which is placed inside the house.  A power jack for the +12v input and a terminal block for the earth ground and sensor wire connections are installed.  Two additional terminals were connected to a siren.  Central to the design is a closed pushbutton switch.  When pressed, the button would test the circuit by simulating a broken fence wire. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 2 Oct 2009

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

Bad Light Bulb Indicator -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor. . . Circuit by David Johnson P.E.-December, 2006

Basement Doorbell Beeper -  If you can't hear your doorbell when you are in your basement try this circuit.  This circuit takes advantage of the 24vac power source located near the furnace.  Using a simple current transformer technique, the circuit sounds a beeper whenever the. . . Circuit by David Johnson P.E.-June, 2000

Basement Remote Doorbell -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Basic Alarm with Delayed trigger  -  The CD4001 quad 2-input NOR gate is a very versatile IC that can be used in an almost infinite variation.  Here we will use it in the application of a simple alarm system .  The power supply suggested for the CD4001 is 5 to 15Vdc Max.  The CD4001 has a typical transition voltage value of 50% of its supply voltage with a possible spread of 30% to 70% depending on its production.   __ Designed by © Laurier Gendron, Burnaby, B.C., Canada

Battery Low Voltage Beeper  -  This circuit provides an audible and visual low voltage warning for 12V battery powered devices.  Idle current: 6ma Low Voltage Warning current: 15ma.   __ Designed by G. Forrest Cook

Battery Powered One Time Alarm Only (Ron J)  -  This is a single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers.  It will accommodate the usual types of normally-closed input devices - such as magnetic-reed contacts, foil tape and PiRs.   __ Designed by Ron J.

Battery-Powered Freezer Alarm  -  A typical freezer can contain hundreds of dollars with of food.  If the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by David Johnson P.E.-July 20, 2006

Battery-Powered One-Time-Only Burglar Alarm  -  Battery-Powered Alarm Circuits:  This is a single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers.  When the alarm is activated its Siren will sound once - for up to 20-minutes.  Then it will switch off and remain off.  If you wish - you can use a mains power supply.  But the extremely low standby current makes battery power a realistic option. __ Designed by Ron J.

Bedwetting alarm  -  A simple two tone water alarm that is light enough to be worn on the upper arm of a sleeper is described.  It uses two LMC555 CMOS timer chips followed by a complimentary pair of emitter followers to drive an 8 ohm speaker.  Power is supplied by a 9 volt transistor radio battery.  An modification to produce a siren rather than two tone operation is discussed __ Designed by Dick Cappels

Bedwetting Alarm  -  Bedwetting is one of the most common childhood problems that can have a significant impact on a child’s health if left unattended.  During the night, the parents would not know if__ Electronics Projects for You

Bedwetting/Wet Diaper Alert System  -  Bedwetting is one of the most common childhood problems that can have a significant impact on a child’s health if left unattended.  During the night, the parents would not know if the child has urinated and the kid may sleep all night long on a wet bed, or with a wet nappy.  Bedwetting/Wet Nappy alert system provides a very __ Designed by T.K. Hareendran

Beeper  -  This circuit produces the sound of a beeper like the one in pagers which produces a "beep-beep" sound.  Basically the circuit consists of a 555 timer oscillator which is turned ON and OFF periodically.
The first IC (left) oscillates at about 1Hz.  The second IC is turned ON and OFF by the first IC .  The first IC determines how fast the second IC is turned ON/OFF and second IC determines the tone of the final output.  By varying the VR1, the changeover rate can be adjusted.  By varying VR2 the tone can be adjusted. __ Designed by Radioland.nt.au

Beeper bug transmitter for fox hunt & vehicle tracking  -  This bug can be attached to anything from a glider to a plant and you can track it with a radio.  Why track a plant? The Beeper is the result of many requests for a minim tracking device and introduces a new world of tracking __ Designed by Collin Mitchell

Bicycle Anti-Theft Alarm  -  I hate to suggest the specific application ‘bicycle’ because it may be use to protect many items from theft.  This anti-theft alarm project is built around the inexpensive Measurement Specialties DT piezo film sensor.  Every now and then everything seems to work out perfectly as in the Yin and Yang of the cosmos, and __ Designed by Jim Keith

Big Ben Sound  -  This circuit produces  famous Big Ben sound.  It produces  "ding dong" sound when switched ON.  Basically  circuit alternates between two frequencies which are adjustable.  This produces  "ding-dong" sound.  The first C (left) oscillates at about 1Hz.  The second IC 's tone is modulated by  changing voltage at  output of  first IC  __ Designed by Radioland.nt.au

Bike Guard Alarm  -  This Simple circuit can be used to Guard your bike from theft.  It gives a loud alarm tone if somebody tries to start the bike.  The alarm disables only when the hide switch S2 is opened.  The circuit has little component count and can be easily fixed in the bike.  Working of the circuit is simple.  The alarm generator buzzer or __ Designed by D Mohankumar

Bite Alarm-Pulsed Tone Generator  -  produces a pulsed tone with adjustable speed, duration, pitch and volume.   __ Contact P. Townshend - EduTek Ltd

Blown Fuse Indicator  -  a simple way to see if a fuse has blown without removing it from its holder __ Designed by Andy Collison

Blown Fuse Indicator  -  Generally, when an equipment indicates no power, the cause may be just a blown fuse.  Here is a circuit that shows the condition of fuse through LEDs.  This compact circuit is__ Electronics Projects for You

Blown Fuse Indicator  -  This blown fuse indicator will work with a wide range of DC supply voltages from 5V to 50V.  It illuminates LED1 when the fuse blows.  With the fuse intact, Q1 is held off and there is no bias current available for the base of Q2.  So the LED is off.  When the fuse blows, a__ 

Blown-Fuse Indicator Sounds an Alarm  -  10-Jul-08 EDN Design Ideas:  A simple blown-fuse-indicator circuit sounds a buzzer and flashes an LED when a fuse blows __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Brakelight Flasher  -  This is basically a flasher circuit modified to turn on and off a bulb instead of a LED.  It uses a 555 timer IC working as an astable multivibrator.  The flashing rate can be varied from very fast to a maximum of once in 1.5 sec by varying  preset VR1.    The ON time of  circuit is given by: TON= 0.  69xC1x (R1 + VR1) second and  OFF time is: TOFF= 0.  69xC1xVR1 second __ Designed by Radioland.nt.au

Bridge Reversal Eliminates 1/f Noise & Offset Drift of a Low Noise, Non-Autozeroed, Bipolar Amplifier  -  This circuit gives 14nV noise level (or 19 effective bits) over a 10mV span.  Bridge reversal eliminates 1/f noise and offset drift of a low noise, non-auto zeroed, bipolar amplifier.  The LTC2440 is a high speed 24-bit No Latency delta sigma ADC with 5ppm in and 5μV offset.  It uses proprietary delta-sigma architecture enabling __ Linear Technology/Analog Devices App Note, Jul 8th 2010

Briefcase Alarm  -  This miniature alarm unit protects your valuables from theft by sounding an alarm when somebody attempts to pick up your briefcase.  It is a battery-operated gadget that can be hidden in__ Electronics Projects for You

Broken Charger-Connection Alert  -  Detects if a device is not properly connected to its supply.    Suitable for battery chargers, portable appliance supplies etc.   __ Contact Flavio Dellepiane, fladello @ tin.it

Broken_Fence_Alarm  -  It was deer hunting season and cattle rancher was fed up with hunters cutting his barbed wire fence, to gain entrance onto his property.  The rancher want to be alerted when the barbed wire was cut.  The circuits below is placed inside a small plastic box which is placed inside the house.  A power jack for the +12v input and a terminal block for the earth ground and sensor wire connections are installed.  Two additional terminals were connected to a siren.  Central to the design is a closed pushbutton switch.  When pressed, the button would test the circuit by simulating a broken fence wire. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 2 Oct 2009

Build a Raucous Alarm  -  it sounds so dreadful, that you cannot ignore it.  And it only uses two IC s.__ SiliconChip

Build a Swimming Pool Alarm  -  Don't wait until summer; build this effective alarm now.  It could save your child's life.__ SiliconChip

Build an iButton electronic lock based around a AT91C2051 microcontroller (includes ASM source code)  -  Since iButton DS1990A introduced in market from Dallas Semiconductor (Maxim) , it has been used in many applications concerning security, access control systems etc.  In this project we will use iButton as a key to an electronic lock.  This electronic lock can use many different kinds of iButtons and can store up to 9 different keys.  One of the keys is the master key and is permanent stored in memory __ Designed by Kyriakos Kontakos

Burglar Alarm System  -  This burglar alarm system circuit is using a infrared proximity detector that triggers an alarm when the rays falling on its sensor are interrupted.  It is different from others burglar alarm systems because is a very simple DIY project and can offer you great satisfaction.  The circuit of IR burglar alarm system comprises __ 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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