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Security Circuits
- including Burglar Alarms, Page 2
Security
Burglar Alarms: #'s - B
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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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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, ...
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Cut Phone Line Alarm
Burglars, rapists and other criminals will
often cut a phone line before they break into a home. The cut phone line will
prevent many alarm systems from alerting the police. The battery powered
circuit below will sound an alarm when the unit no longer detects the voltage
present on an active phone line....
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Links to electronic circuits, electronic schematics, designs for engineers, hobbyists,
students & inventors: |
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Car Alarm and Immobilizer - This circuit features automatic exit
and entry delays - an optional instant alarm zone - an optional
intermittent siren output - and an automatic reset. By adding external
relays you can immobilize the vehicle and flash the lights…. [Design by
Ron J.] |
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Car Alarm Sound Booster - For car alarms, emphasis should be put
on hearing the audible alert and identifying it as belonging to your
‘wheels’.….must register on this site.... [Published in Elecktor
July/August 2010] |
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CMOS 4060 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…. [Circuit design by Ron J.] |
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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,...(Circuit design added
06/07/08) |
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CMOS Based Motorcycle Alarm - This circuit features automatic
Exit/Entry delays, timed Bell Cut-off and System Reset. It has provision
for...(Circuit design added 006/07/08) |
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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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Combination Digital Lock - A multiple input combination loack using CMOS
counter IC's. Flexibility and code change is allowed by changing output connections….
[Circuit designed by Andy Collison] |
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Combination Lock PIC16F84 - (Circuit design added 8/03)
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Cut Phone Line Alarm - Burglars, rapists and other criminals will
often cut a phone line before they break into a home. The cut phone
line will prevent many alarm systems from alerting the police. The
battery powered circuit below will sound an alarm when the unit no
longer.... [Designed by David A. Johnson] |
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Cut Phone Line Detector - 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.... [Arron
Cake] |
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Cut Phone Line Detector - 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.... [Tony van Roon's circuit] |
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DayLight Alarm - The circuit presented here wakes you up with a loud alarm
at the break of the daylight. Once again the 555 timer is used here. It is working as
an astable multivibrator at a frequency of about 1kHz…. [Radioland.nt.au] |
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Digital Combination Lock - A multiple input combination loack using CMOS
counter IC's. Flexibility and code change is allowed by changing output connections.
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Digital Electronic Lock (Bill Bowden) - The digital lock shown below uses 4
common logic ICs to allow controlling a relay by entering a 4 digit number on a
keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are
gated....(electronic schematic / circuit added 11/05) |
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Door/window sensor resists tampering - 01/21/99 Issue of EDN The
simple, inexpensive circuit in Figure 1 detects a failure (or deliberate tampering] on
lines connected to normally closed switch sensors. For example, common door interlocks
and door/window sensors consist of normally open or normally closed magnetic reed
switches. Depending....Page includes several designs. Scroll to find this
one.... [Design Idea by Paul Nocella, Q Research, Brookline, NH] |
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Security Burglar Alarms: #'s - B
C - D E - G
H - L
M - O P
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T - Z |
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