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12 Volt Alarm Power Supply - (circuit / schematic design added 6/06) |
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2-input alarm - This article describes a 2-Input alarm developed on the PIC LICK-1
Module using a Microchip PIC16F628-04. The program uses the internal 4MHz
oscillator and if any other frequency is used, the timer values will need to be
changed.....(electronic circuit added 05/06/07) |
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4 Digit Keypad - (diagram added 6/03) |
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4-Digit Alarm Control Keypad - This Keypad is suitable for the Modular Burglar
Alarm. However, it has other applications. Pressing a single key will energize the
relay. Entering the Four-Digit code of your choice will de-energize it. (circuit
design added 08/08/08) |
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5 Zone Alarm Circuit - (electronic schematic added 8/02) |
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5 Zone alarm circuit MIT - (schematic added 2/07) |
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555-Timer Based Motorcycle Alarm - This circuit features an intermittent siren
output and automatic reset. It can be operated manually using a key-switch or a hidden
switch; but it can also be wired to set itself automatically when you turn-off the
ignition. By adding external relays you can immobilize the bike, flash the lights etc.
(circuit design added 08/08/08) |
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5-Digit Alarm Control Keypad - This Keypad is suitable for the Modular Burglar
Alarm. However, it has other applications. Entering the First Four Digits of your
chosen Five-Digit code, will energize the relay. Entering the Full Five-Digit code,
will de-energize it. (circuit design added 08/08/08) |
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A 4-Digit Keypad Controlled Switch - This is a Universal version of the Four-Digit
Alarm Control Keypad. I have modified the design to free up the relay contacts. This
allows the circuit to operate as a general-purpose switch. I've used a SPCO/SPDT
relay, but you can use a multi-pole relay if you wish....(electronic schematic added
05/09) |
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A 555-Timer Based Motorcycle Alarm - This circuit features an intermittent siren
output and automatic reset. It can be operated manually using a key-switch or a hidden
switch; but it can also be wired to set itself automatically when you turn-off the
ignition. By adding external relays you can immobilize the bike, flash the lights etc.
(circuit design added 08/08/08) |
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A 5-Digit Alarm Control Keypad - This Keypad is suitable for the Modular Burglar
Alarm. However, it has other applications. Entering the First Four Digits of your
chosen Five-Digit code, will energize the relay. Entering the Full Five-Digit code,
will de-energize it. (circuit design added 08/08/08) |
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A Battery-Powered One-Time-Only Burglar Alarm - 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. (circuit design added
08/08/08) |
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A CMOS 4060 Burglar Alarm - This is a single zone alarm, with automatic exit,
entry and siren cut-off timers. It will accommodate all the usual types of
normally-closed input devices, such as magnetic reed contacts, foil tape, PIRs etc.
But it's easy to add a normally-open trigger....(circuit design added 06/07/08) |
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A CMOS Based Motorcycle Alarm - This circuit features an intermittent siren
output and automatic reset. It can be operated manually using a key-switch or a hidden
switch; but it can also be wired to set itself automatically when you turn-off the
ignition....(circuit design added 06/07/08) |
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A CMOS Based Single Zone 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 will accommodate the usual input devices (Pressure Mats,
Magnetic Reed contacts, Foil Tape, PIRs and Inertia Sensors)....(circuit design added
006/07/08) |
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A CMOS Based Vehicle Anti-Theft Alarm - This car alarm circuit features Exit and
Entry delays, an instant alarm zone, an intermittent siren output and automatic Reset.
By adding external relays you can immobilize the vehicle and flash the
lights….(circuit design added 06/07/08) |
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A CMOS Single Zone Intruder Alarm - This circuit features automatic Exit and Entry
delays, timed bell cut-off, and system reset. It has provision for normally-open and
normally-closed switches, and will suit all of the usual input devices (Pressure Mats,
Magnetic Reed contacts, Foil Tape, PIRs and Inertia-Sensors, see....(schematic added
95/09) |
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A Dozen Small CMOS Alarm Circuits - This is a selection of small self-contained
alarm circuits. They have a very low standby current; and are suitable for battery
operation. Some are triggered by normally-open and normally-closed switches. Some
react to changes in light or temperature. The result is a variety of output times and
patterns. (circuit design added 04/05/06) |
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A One-Time-Only Burglar Alarm - When this alarm is activated its Siren will sound
once, for up to 20-minutes. Then it will switch off and remain off. The basic circuit
has a single zone with independently adjustable Exit and Entry delays. This will be
adequate in many situations. However, there's also range of Expansion Modules. These
will allow you to add any number of Instant Zones, Tamper Zones and Personal Attack
Zones to your system. (circuit design added 04/05/06) |
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A Shed/ Garage Alarm - This is a basic single-zone burglar alarm circuit. Its
features include automatic Exit and Entry delays. It has an extremely small standby
current. This makes it ideal for battery-powered operation. Use it in your caravan,
mobile home, lock-up, or anywhere mains power is not available. (circuit design
added 04/05/06) |
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A Simple Fire-Door Alarm - This circuit will let you know when something that
should be kept closed, has in fact been left open. Attach it to a Fire-Door. It will
allow you to pass through the door as usual. However, if it's left open for more than
30-seconds or so, the buzzer will sound. Photo (circuit design added 04/05/06) |
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A Simple Shop-Door Alarm - Attach this circuit to the door of an unattended shop,
or reception area, and the sound of the buzzer will tell you when you have a customer.
Add a siren, and it becomes a simple intruder alarm. Photo (circuit design added
04/05/06) |
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A Simple Transistor Based Motorcycle Alarm - This is an even simpler transistor
based motorcycle alarm. The circuit features a timed output and automatic reset. It
can be operated manually using a key-switch or a hidden switch. By adding an external
relay, it will set itself automatically, and/or immobilize the machine, every time you
turn-off the ignition. It's easily adapted for a 6-volt system, so it will protect
your "Classic Bike"(circuit design added 04/05/06) |
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A Simpler CMOS Single Zone Alarm - This circuit features automatic Exit/Entry
delays, timed Bell Cut-off and System Reset. It will accommodate the usual
normally-closed input devices (Magnetic Reed contacts, Micro Switches, Foil Tape and
PIRs). And, with a simple modification, a normally-open trigger may be added .
(circuit design added 04/05/06) |
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A Transistor Based Motorcycle Alarm - This circuit features a timed output and
automatic reset. It can be operated manually using a key-switch or a hidden switch. By
adding an external relay, it will set itself automatically, and/or immobilize the
machine, every time you turn-off the ignition. It's easily adapted for a 6-volt
system, so it will protect your "Classic Bike". (circuit design added 04/05/06) |
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AC Line Under/Over Voltage Alarm - Power lines, which deviate much beyond normal
voltages can damage expensive electronic equipment. The circuit below sounds an
alarm whenever the line voltage is higher or lower than normal. I set the alarm
limits at about +-15% from standard levels. The circuit rectifies and filters
the power line signal. I set the resistor values, so the DC voltage produced is
close to 1% of the RMS value of the line. Thus, a 120vac line would yield about
1.2v DC. That voltage is fed to a pair of voltage comparators. The outputs
of the comparators decide if the sampled voltage is above, below or acceptable. ....
….(designed by David A. Johnson) |
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Alarm Circuit - Surround your Entire Yard with this Laser Alarm ….(circuit
design added 12/08) |
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Alarm control keypad - (diagram added 1/07) |
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Alarm monitors rotational speed of DC motor - 10/02/08 EDN-Design Ideas: This
Design Idea monitors the rotating speed of a dc fan motor, sounding an alarm and
powering down if the motor stalls.....(design idea added 11/08) |
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Alarm Power Supply - ….(circuit design added 03/08) |
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Alarm Power Supply With Battery Back-up - 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....(circuit design added 08/08/08) |
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Alarm System - (design added 8/03) |
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Alarm tells you to close the refrigerator door - 06/25/09 EDN- Design Ideas,
A simple gadget that you place inside the refrigerator alerts you by beeping if the
door stays open for 20 seconds or longer.....(design idea added 08/09) |
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American Police Car Siren (linscott) - Scroll down to locate this circuit. The 555
on the right is wired as an alarm tone generator and the second 555 timer on the left
is wired as a low frequency astable timer which generates a ramp waveform of about 6
seconds that is buffered by the transistor and again used to frequency modulate the
tone generator. The transistor is used to help strengthen the signal to the
speaker....(electronic design added 08/08/08) |
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An Enhanced Shed/ Garage Alarm - This is an enhanced version of the simple
Garage/Shed Alarm. The Entry and Exit delays have been increased to about 30-seconds,
and 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. Photo (circuit design added 04/05/06) |
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An Expandable Multi-Zone Modular Burglar Alarm - 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. (circuit design added 04/05/06) |
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An Expandable SCR Based Burglar Alarm - This is a simple SCR based burglar alarm
circuit. Its features include automatic Exit and Entry delays, together with a timed
Bell Cut-off and Reset. The basic alarm has a single zone. This will be adequate in
many situations. However, the 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.
(circuit design added 04/05/06) |
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An Expandable Transistor Based Burglar Alarm - This transistor based alarm
features automatic Exit and Entry delays, together with a timed Bell Cut-off and
system Reset. Along with the Exit/Entry zone, the basic alarm board has one Instant
Zone. This will be adequate in many situations. However, the 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. (circuit design added 04/05/06) |
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An SCR Based Burglar Alarm - (electronic design added 6/07) |
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Anit Theft Motorcycle Alarm - (schematic added 9/02) |
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Auto Burglar Alarm (Randy Linscott) - This alarm circuit is based on two 555
timers. The alarm will sound your car horn if anyone opens the car door while the
circuit is armed. The timers will allow you to leave the car without sounding the
horn. To turn the circuit on S1 must be closed.….(added 08/08/08) |
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Automatic Intruder Alarm - (electronic design added 6/07) |
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Automatic Night Lamp with Morning Alarm - (electronic Circuit / Schematic added
10/04) |
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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…. (schematic added 9/02) |
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Battery-Powered One-Time-Only Burglar Alarm - 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. |
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Beeper bug transmitter for fox hunt & vehicle tracking - (diagram added 05/07) |
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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..... (added 10/05) |
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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 ....
(added 10/05) |
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British Police Car Siren - The first circuit simulates the siren of a British
police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an
alarm tone generator and the second 555 timer on the left is a 1 Hz astable
multivibrater....(electronic design added 08/08/08) |
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Broken Charger-Connection Alert - Detects if a device is not properly connected to
its supply. Suitable for battery chargers, portable appliance supplies etc.
(added 3/050 |
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Burglar Alarm - This is a single zone alarm, with automatic exit, entry and siren
cut-off timers. It will accommodate all the usual types of normally-closed input
devices, such as magnetic reed contacts, foil tape, PIRs etc. But it's easy
...(electronic design added 7/08) |
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Car Alarm - (application / block diagram added 6/07) |
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Car Alarm & 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 vehicle and flash lights..... (added
10/05) |
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Car Anti-Theft Wireless Alarm - This FM radio-controlled antift alarm can be used
with any vehicle having 6to 12-volt DC supply system. The mini VHF, FM transmitter is
fitted in vehicle at night when it is parked in car porch or car park. The
receiver unit with CXA1019, a single IC-based FM radio module, which is freely
available in market at reasonable rate, is kept inside. Receiver is .... (added
10/05) |
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Car Back-up Alarm - The brake lights of automobile trigger this circuit on
and off. This save annoyance of alarm when it is not needed.
This is an older circuit which was published in Popular Electronics Magazine, but
still a good circuit today. (Tony van Roon's electronic design added 6/06) |
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Car HiJack Alarm - Before fitting this or any other engine cut-out to your
vehicle, carefully consider both the safety implications of its possible failure, and
the legal consequences of installing a device that could cause an accident. If you
decide to proceed, you will need to use the highest standards of materials and
workmanship.....(electronic design added 6/07) |
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Car-Police Siren - This siren circuit simulates police, fire or other emergency
sirens that produce an up and down wail. (circuit design added 08/08) |
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Chain Link Fence Alarm - Long stretches of steel fence can be monitored using the
simple circuit below. An insulated wire is woven through the links in the fence.
Where the fence begins, the circuit is connected to an earth ground and the security
wire. At the end of the fence, the wire is connected to one of the steel posts, held
in the ground. The typical earth ground resistance will be in the 1000s of ohms
range, which is low enough to keep the n-channel FET turned off in the circuit below.
If the wire is cut or broken, ... ….(designed by David A. Johnson) |
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Cmos 4017 Sequential Timer - This circuit uses a Cmos 4017 decade counter to
create a sequence of four separate events. The number of events in the sequence may be
increased to nine or ten. And the length of each event is controlled independently.
D13 causes the sequence to repeat continuously. If you leave out D13, the sequence
will run only once. I've used a 12-volt supply in the diagram, but the circuit will
work at anything from 5 to 15-volts....(circuit added 02/09) |
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CMOS 4060 Burglar Alarm - This is a single zone alarm, with automatic exit, entry
and siren cut-off timers. It will accommodate all the usual types of normally-closed
input devices, such as magnetic reed contacts, foil tape, PIRs etc. But it's easy to
add a normally-open trigger....(circuit design added 06/07/08) |
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CMOS Based Motorcycle Alarm - This circuit features an intermittent siren output
and automatic reset. It can be operated manually using a key-switch or a hidden
switch; but it can also be wired to set itself automatically when you turn-off the
ignition....(circuit design added 06/07/08) |
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CMOS Based Vehicle Anti-Theft Alarm - This car alarm circuit features Exit and
Entry delays, an instant alarm zone, an intermittent siren output and automatic Reset.
By adding external relays you can immobilize the vehicle and flash the
lights….(circuit design added 06/07/08) |
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CMOS Single Zone Alarm - (diagram added 6/03) |
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Cold Activated Switch - The thermistor used has a resistance of 15k at 25 degrees
and 45k at 0 degrees celsius. A suitable bead type thermistor is found in the Maplin
catalogue. The 100k pot allows this circuit to trigger over a wide range of
temperatures. A slight amount of hysteresis is provided by inclusion of the 270k
resistor. This prevents relay chatter when temperature is near the switching threshold
of this circuit. (added 2/06) |
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Cold Activated Switch (Andy Collinson) - A simple thermistor triggered cold switch
with adjustable threshold. (added 10/05) |
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Combination Digital Lock - A multiple input combination loack using CMOS counter
IC's. Flexibility and code change is allowed by changing output connections.
(schematic added 9/02) |
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Combination Lock PIC16F84 - (diagram added 6/03) |
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Combination Lock-Digital - (electronic design added 6/07) |
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Controller Provides Multiple Alarm Driver Formats - 01/15/98 EDN-Design Ideas:
DC/DC converters for use inside the telephone handset require operation from the
high-source-impedance phone line. Additionally, the CCITT specifications call for
maximum on-hook power consumption of 25 mA. The dc/dc converter in Figure 1 is
70%-efficient at an input power of 25 mA, providing 5V at 3.4 mA. Controlled, low-peak
switch current ensures that the 48V input line experiences no excessive voltage drops
during switching.....(design idea added 06/06/06) |
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Countersurveillance Monitor - This simple-to-build, yet effective circuit can help
you search out and remove electronic eavesdropping devices….(Tony van Roon's
electronic design added 6/07) |
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Cut Phone Line Detector (Aaron Cake) - A while ago I got an email asking for the
schematic of a circuit to detect cut phone lines. It didn't take me long to find this
circuit in Electronics Now. 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 a security system. (added 04/03/02) |
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Cut Phone Line Detector (Tony van Roon) - This circuit speaks for itself.
When the phone line is okay, Q1 acts as a short with a very high ohms value via R1,
R2, and R3 for a total of about 66 MegOhm so very high. When the phone line is cut
(Tony van Roon's open), it activates the MosFet (Tony van Roon's Q3) via transistor Q2
to drive the load. Substitutes are fine, none of the components are
critical....(Tony van Roon's schematic / circuit added 10/02) |
