Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com, has 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.
We make every effort to link to original material posted by the designer. 
Please let us if you would like us to link to or post your design.

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


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

 

Last Updated: December 07, 2017 02:03 PM

 

Circuits Designed by Dave Johnson, P.E.

Micro Power Over-Temperature Alarm -  The circuit is powered for years by a single 3 volt lithium battery.  It sounds an alarm when the temperature exceeds a certain point.  With some minor changes the circuit could also be configured for an under temperature (freeze) alarm.  The circuit uses a. . . Circuit by Dave Johnson P.E.-June, 2000

Monitors Pump Motor -  This circuit solves this problem in a novel way.  It clips on the outside of the pump motor’s power cable and provides a transistor switch closure whenever the circuit detects current flowing to the motor.  The circuit draws so little current that a small lithium cell will power the circuit for yearsCircuit Solution by David A. Johnson P.E.-November, 2004

Next-Generation Star-Trek Doorbell -  In the Star Trek “Next Generation” TV series, the doorbell outside the private quarters of a crew member makes a particular “beep-boop” sound.  The 3v battery powered circuit below tries to simulate this sound.  The circuit uses one 74HCT74 dual D flip/flop . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2001

Over-Temperature Micro-Power Alarm -  The circuit is powered for years by a single 3 volt lithium battery.  It sounds an alarm when the temperature exceeds a certain point.  With some minor changes the circuit could also be configured for an under temperature (freeze) alarm.  The circuit uses a . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Power Loss Beeper -  For some medical equipment it is important for an operator when power is lost to the machine.  The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts. . . Circuit by David Johnson P.E.-March, 1999

Pump Motor Monitor -  This circuit can turn on a light or sound a beeper, whenever an AC line powered pump motor turns on.  It is designed to detect the motor current using a small inductor placed on the outside of the motor’s power cable.  No direct wire contact is needed. . . Circuit by David Johnson P.E.-November, 2004

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

Police Car 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.

Police Siren -  The Police Siren circuit uses two 555's to produce an up-down wailing sound.  The first 555 is wired as a low-frequency oscillator to control the VOLTAGE CONTROL pin 5 of the second 555.  /. __ 555-Timer

Police Siren -  This circuit produces a sound similar to the police siren.  It makes use of two 555 timer ICs used as astable multivibrators.  The frequency is controlled by the pin 5 of the IC.  The first IC (left) is wired to work around 1Hz.  The 47uF capacitor is charged __ Designed by Radioland.nt.au

Power Fail Alert -  In this circuit an electricity supply (domestic or industrial) is continually monitored.  Should the supply be interrupted then an alarm will sound for the duration of the interruption.  It has battery backup and overcharge protection. __ Designed by Andy Collison

Power Failure & Resumption Alarm -  This circuit gives audio-visual indication of the failure and resumption of mains power.  The circuit is built around dual timer IC LM556.  When mains is present the bicolour LED glows in __ Electronics Projects for You

Power Failure Alarm -  This is a very basic alarm designed to let you know when the electricity supply fails.  The alarm is powered from a battery which uses no current consumption at all in standby, a battery should therefore last its full shelf life. __ Designed by Andy Collison

Power Line Alarm -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David Johnson P.E.-July, 2006

Power Loss Beeper -  For some medical equipment it is important for an operator when power is lost to the machine.  The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts. . . Circuit by David Johnson P.E.-March, 1999

Power Resumption Alarm -  Here is a simple power resumption alarm circuit that can be fixed inside the switch box itself.  It gives beeps when the power resumes after a power failure.  This circuit is ideal to monitor battery chargers, since the long duration power failure may sometimes remain unnoticed.  The circuit is too simple and derives power supply __ Designed by D Mohankumar

Power Resumption Alarm & Low-Voltage Protector -  The circuit described here protects your electrical appliances like AC motors from damage due to low voltage at power-on.  It remains standby without giving power to the load after power resumes. __ Electronics Projects for You

Power supply failure alarm -  This is a circuit for a power supply failure alarm.  It requires no separate supply for itself.  It uses a capacitor to store enough charge for the alarm to sound for about one minute in case of a power failure. __ Designed by Electronicsforu

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 source.  It employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit which sounds an alarm for a reasonable duration when the supply fails.

Powerful buzzer for use as a doorbell -  How often on average do you have to call members of your family each day to tell them that dinner is ready, it’s time to leave, and the like? The person you want is usually in a different room, such as the hobby room or bedroom.  A powerful buzzer in the room, combined with a pushbutton at the bottom of the stairs or in the kitchen, could be very handy in such situations __ Learning Electronics

Powerful Security Siren-Transistors based -  This circuit was requested by several correspondents.  Its purpose was to obtain more power than the siren circuit already available on this website (One-IC two-tones Siren) and to avoid the use of ICs.  A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker.  Q1 ensures a full charge of C2 when power is applied to the circuit __ Learning Electronics

Power-line outage flashes red alert -  06/13/02 EDN-Design Ideas This design idea expands on a circuit in a previous one to configure a power-outage detector with a flashing alarm(Figure 1, Reference 1].  The circuit plugs into a mains outlet and uses trickle-charged nickel-cadmium batteries.  The green-LED monitors the presence of line voltage.  The BZV55-C4V3 zener diode, D1 protects the batteries against overvoltage __ Circuit Design by Vasiliy Borodai, Zaporozhje, Ukraine

Power-On Reminder with LED Lamp -  Many a times equipment at workstations remain switched on unnoticed.  In this situation, these may get damaged due to overheating.  Here is an add-on device for the workbench power supply that __ Electronics Projects for You

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 source. __ Designed by M.K. CHANDRA MOULEESWARN

Precision Receiver Battery Low Voltage Alarm -  Flying hand launch gliders means living with small capacity receiver NiCad battery packs.  These small packs are light, but have the distinct disadvantage of rapidly depleting.  You can carefully time your flights, but you end up either crashing when your plane seizes or using only a portion of the already small capacity of the battery.  If you charge the battery in a slightly suboptimal fashion, your plane dies and bites the dirt (done that, crashed).  This devices will allow you to use a small mA pack and use the full capacity of your battery. __ Contact: IQ Technologies

Pressure Sensor Alarm -  General purpose circuit of the simple pressure sensor alarm is built around a couple of readily available cheap components.  Working of this circuit is straight forward and self-explanatory.  When the circuit is powered by a 9V compact battery, the active piezo-sounder at the output of IC1 starts beeping for a short time and __ Designed by Popescu Marian

Pressure-Sensitive Alarm -  Here is a low-cost, pressure-sensitive burglar alarm.  The alarm uses a home-made pressure sensor, which works as a variable capacitor using two copper-clad boards and a piece of sponge in between __ Electronics Projects for You

Programmable Home Security Alarm System. Part 1. Schematic -  Part 1.  In this project we design low cost high performance programmable home security system using few LDR's as an input sensors.  When above sensor(s) get triggered system may dial the user specified phone number (using build-in DTMF generator) and activate the high power audio alarm and lights.  All the parameters of DTMF generator, audio alarm and light interface are programmed through the RS232 serial interface.

Programmable Home Security Alarm System. Part 2. Calibration & Testing -  Part 2.  Schematic Calibration and Testing.   Once everything is assembled take following steps to calibrate the system, Remove IC1, IC2, IC3 and IC4 from the IC bases.  Apply 18V (to 22V Max.) DC source to the power connector (J3).  Check the voltage

Proximity Alarm -  This simple circuit is sure to have the police beating a path to your door, however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat.  The circuit transmits on Medium Wave (this is the small problem with the police).  IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates __ Designed by Rev. Thomas Scarborough

Pseudo car Alarm systE - M -  I owned a S10 Chev pick-up which was parked in the underground of my building.  It was broken into.  They broke some windows and tried to steal the stereo.  It was a mess.  Later the vehicle was stolen.  When the cops found it the ignition key system was damaged and it had been stripped clean of everything that hadn't been bolted down. __ Designed by Laurier Gendron, Coquitlam , B.C., Canada

Pseudodifferential Multichannel Bridge Digitizer & Digital Cold Junction Compensation -  This circuit enables pseudodifferential measurements of several bridge transducers and absolute temperature measurement.  Consecutive readings are performed on each side of the bridge by selecting the appropriate channel on the LTC2428.  Each output is digitized and the results digitally subtracted to obtain the pseudodifferential __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Pull-Pin Security Alarm -  Here is a simple and low-cost circuit of pull-pin security alarm.  While travelling, rig the alarm unit to your luggage using a home-made security cable.  When somebody tries to cut or __ Electronics Projects for You

Pulsed alarm -  Sometimes the need arises for a simple, gated, pulsed alarm.  The circuit shown here employs just four components and a piezo sounder and is unlikely to be out-done for simplicity.  While it does not offer the most powerful output, it is likely to be adequate for many applications.  A dual CMOS timer IC type 7556 is used for the purpose, __ Learning Electronics

Pump Motor Monitor -  This circuit can turn on a light or sound a beeper, whenever an AC line powered pump motor turns on.  It is designed to detect the motor current using a small inductor placed on the outside of the motor’s power cable.  No direct wire contact is needed. . . Circuit by David Johnson P.E.-November, 2004

Pyroelectric Fire Alarm -  Here is an ultra-sensitive fire sensor that exploits the direct piezoelectric property of an ordinary piezo element to detect fire.  The lead zirconate titanate crystals in the piezo element have the __ Electronics Projects for You

      <<<      

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


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |    Privacy Policy


Copyright  January, 1998 - December, 2017     David A. Johnson & Associates.  All Rights reserved. 


 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.