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Alarm Circuits Page
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Alarms: #-C
D-G
H-O
P-R
S
T-U
V-Z
Last Updated on:
Monday, October 03, 2011 06:07 PM
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Circuits Designed by Dave Johnson, P.E. |
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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Perimeter Monitor - Using a single cable such as speaker wire or
doorbell cable, this circuit can be remotely positioned, for example,
at the bottom of a garden or garage, and used to detect all sound in
that area. The cable can be buried in a hosepipe or duct and is
concealed out of sight. The mic is an ordinary dynamic mic insert....
[Circuit design by Andy Collison] |
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Personal Alarm - This one is particularly loud even though it
runs on only two AA batteries. It uses a Push Pull transformer
output... [Reverse engineered schematic by Stepan Novotill] |
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Personal Alarm redcircuits - Small portable, anti-bag-snatching
unit. Also suitable for Doors and windows control (added 9/04)
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PIC16F84 Alarm Clock - This is an alarm clock I built. It was
very effective during the sort time I used it, because I programmed it
to play a very annoying tune through a speaker. I actualy started to
wake up before the alarm went of, so other people int he house didn't
wake up from the anoying pitches it played. The Jal sourcecode is
available on my download page Features * Timekeeping ….(Circuit design
added 11/08) |
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PIR Motion Detector - (diagram added 6/03) |
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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../.. |
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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.... [Radioland.nt.au] |
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Police Siren - This siren circuit simulates police, fire or other emergency sirens
that produce an up and down wail. (added 10/05) |
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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. [Andy
Collison] |
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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.
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Power Supply Failure Alarm - This circuit.... (added 10/05) |
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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.... [Radioland.nt.au] |
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Power-line outage flashes red alert - 13-Jun-02 Issue of EDN 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.... [Design Idea by
Vasiliy Borodai, Zaporozhje, Ukraine] |
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Power-Supply Failure Alarm - (electronic Circuit / Schematic added 10/04)
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| Precision Receiver Battery Low Voltage Alarm -
….(design added 08/08) [Site is underconstruction right now] |
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Proximity alarm - Schematic only, no circuit description |
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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.... [Circuit design by Rev. Thomas Scarborough] |
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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.... [Designed by David A. Johnson] |
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R/C Emergency Locator Alarm - (electronic circuit added 4/05) |
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Radio Wave 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.... [Rev. Thomas Scarborough] |
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Rain Alarm - This circuit consumes no current until moisture is detected on the rain
plate. |
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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
water. The sensor when wetted by water completes the circuit and makes the 555 oscillate
at about 1kHz. [Radioland.nt.au] |
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Rain Detector (Aaron Cake) - This circuit uses a sensor made of a small piece of
etched PC board and a simple SCR circuit to detect rain and sound a buzzer. The SCR could
also be used to activate a relay, turn on a lamp, or send a signal to a security system….
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Receiver Battery Low Voltage Alarm - [Site is underconstruction right now] |
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Red Alert Alarm, #1 - The circuit above provides a 'pulse-tone', like the one you
know from the old Star Trek. The output stage contains a power-booster with Q1 (2N3055),
providing several watts to the loudspeaker SPKR1. Clamping diodes are used to limit the
speaker's inductive kickback to a safe level. To prevent the output signal from feeding
back into the 555's via the supply line, the supply lines are filtered by a capacitor and
an isolating diode (C5 and D2).... [Tony van Roon's circuit] |
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Red Alert Alarm, #2 "Red Alert" 555 Siren …. [Tony van Roon's circuit] |
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Red Alert Star Trek Alarm - Scroll down to locate this circuit. The third circuit
simulates the "Red Alert" siren from the TV show Star Trek. 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 wired as a 1.5 second non-symmetrical....(electronic design added 6/07)
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Refrigerator Door Alarm - Do your kids leave the door to the refrigerator open? Or
does your celery reach out to keep the door from closing properly when you turn your back?
Here's a simple circuit that beeps whenever the door is open for an extended period of
time (which will also put a little pressure on the fridge loiterers in the house)....
[Circuit designed by Charles Wenzel] |
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Refrigerator Pig Schematic - Upon opening your fridge door the photocell is exposed
to light and the piggy oinks…. [Reverse engineered schematic by Stepan Novotill] |
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Reverse warning device - The car that is equipped with the reverse lamp. In the case
that it is not equipping, it's a defective car.….(added 05/08) |
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RF 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....(diagram added 6/03) |
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RF Transmitter for PIR Sensors - (diagram added 6/03) |
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Alarms:
#-C
D-G
H-O
P-R
S
T-U
V-Z
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