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Head Light Alarm - "Never forget to turn off your head light ever again! Most
newer cars already have this feature built-in but there are still lots of cars out there
without it. This simple circuit is cheap and can be built for
about $5 bucks!"...(Tony van Roon's circuit added 08/09) |
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Highway Alert Signal Lamp - (electronic Circuit / Schematic added 10/04) |
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Hijack Alarm (Ron J) - The first circuit was designed for the situation where a hijacker
forces the driver from the vehicle. If a door is opened while the ignition is switched on,
the circuit will trip. After a few minutes delay, when the thief is at a safe distance, the
alarm will sound and the engine will fail....(added 10/05) |
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Home Security Project - (diagram added 6/03) |
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How To Measure the Switching Voltage & Hysteresis Of A Cmos Gate - Manufacturing
tolerances mean that the switching characteristics of Cmos ICs vary from one batch to the
next. This page provides two small circuits that will allow you to measure the exact
switching voltage of common Cmos inverters and non-inverters. |
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Human Traffic Footstep Alarm - This circuit processes the amplified signals from the
footstep detector circuit and activates a microprocessor when the circuit detects footsteps.
At has an adjustable sensitivity.
.(designed by David A. Johnson) |
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Intruder Radio Alert System - (electronic Circuit / Schematic added 10/04) |
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Keypad Controlled Switch No. 2 - This is a simplified version of the 4-Digit Keypad
Controlled Switch. I have modified the design to reduce the complexity of the circuit, and
the number of components required. As a result, the code is somewhat less secure. However,
there should be lots of situations where it will still be adequate. (circuit design
added 08/08/08) |
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Knock Alarm (Sunil Kumar) - his circuit (Fig. 1), used in conjunction with a thin
piezoelectric plate, senses the vibration generated on knocking a surface (such as a door or
a table) to activate the alarm. It uses readilyavailable, low-cost components and can also
be used to safeguard motor vehicles....(electronic Circuit / Schematic added 10/04) |
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Light-Sensitive Alarm - The circuit detects a sudden shadow falling on the light-sensor
and sounds the bleeper when this happens. The circuit will not respond to gradual.....
Designed by John Hewes (added 09/05) |
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Low Power RFID Transponder - For some time railroad companies have been wrestling with
the problem of tracking rail cars. This has traditionally required manual log entry of
identification numbers displayed on the cars as they pass through the switching
yard
.(diagram added 7/03) |
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Low Voltage 120vac Power Line Alarm - This circuit will turn on a beeper when the line
voltage drops below 100 volt AC.
.(designed by David A. Johnson) |
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Low Voltage Alarm (Aaron Cake) - NE555 Low Voltage Battery Disconnect Circuit (added
04/03/02) |
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Luggage Security System - (electronic Circuit / Schematic added 10/04) |
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Machine 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.
.(designed by David A.
Johnson) |
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Melody Generator for Greeting Cards - .... (added 10/05) |
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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 cheap but accurate thermistor as the temperature sensor.
.(designed by
David A. Johnson) |
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Mini Alarms - This is a selection of small self-contained alarm circuits. They have a
very low standby current; and are suitable for battery operation. (added 10/05) |
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Miniature Loop Alarm mitedu - (electronic schematic added 8/02) |
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Modular Burglar Alarm (mba) - 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. It is connected permanently to the 12-volt supply
and its operation is "enabled" by opening SW1l...(electronic schematic added 8/02) |
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Modular Burglar Alarm (Ron J) - The Basic Alarm Circuit has an automatic Exit/Entry
Zone, an Instant Alarm Zone that will accept both normally-closed and normally-open
triggering devices, and an "Always On" 24-hour Personal Attack/Tamper Zone. By using the
Expansion Modules, you can add as many extra alarm zones as you require....(added 05/06/07) |
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Motion Alarm - Using a piezoelectric device, this circuit will activate a beeper
whenever the circuit is moved. It could be used as an earthquake alarm.
.(designed by
David A. Johnson) |
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Motion Alarm Using Piezoelectric Device - An inexpensive piezoelectric device is used as
a motion sensing device for this motion alarm. This circuit will activate a beeper whenever
the circuit is moved. It could be used as an earthquake alarm. (added 7/06)
.(designed by David A. Johnson) |
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Motion Shadow Alarm - This simple circuit uses two inexpensive PIN photo diode light
detectors to detect nearby motion. Any shadow which is cast over the two diodes from a
moving object produces a slight voltage change between the two diodes. When this
change is detected, an alarm switch is activated. Posted
.(designed by David A. Johnson) |
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Motorcycle Alarm - Any number of normally open switches may be used. Fit the mercury
switches so that they close when the steering is moved or when the bike is lifted off its
side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable
panels and the lids of panniers etc...(circuit design added 8/03) |
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Motorcycle Alarm No.3 (Ron J) - 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
added10/05) |
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Motorcycle Alarm Number (Ron J) - 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. Ron has....(added 10/05) |
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Motorcycle Alarm Number 3 - 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..(electronic design added
6/07) |
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Motorcycle Alarm Number 4 - This is a simple easy to build transistor based motorcycle
alarm. It's designed to work at 12-volts. But if you change the relay for one with a 6-volt
coil it'll protect your "Classic Bike". The standby current is virtually zero so it won't
drain your battery. (added 10/05) |
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Motorcycle Alarms Numbers 5 & 6 - These are two easy to build relay-based alarms. You
can use them to protect your motorcycle but they have many more applications. If you use
relays with 6-volt coils they'll protect your "Classic Bike". Both alarms are very small.
The completed boards occupy about half a cubic-inch 8 cc. The standby current is zero so
they won't drain your battery. (added 10/05) |
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N/O: N/C Timed Burglar Alarm - This is a simple but effective alarm circuit which can
reset its self after a time that you select. it has normally open and normally closed
triggers which make this circuit very practical. This alarm has normally open and normally
closed triggers. It's on a 555 timer so the alarm will reset it's self after a certain
amount of time. The time is adjustable.... (added 10/05) |
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Novel Buzzer - (diagram added 6/03) |
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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, ....(circuit design added 05/08) |
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Open door alarm prevents accidental defrosts - 02/01/07 EDN-Design Ideas: Circuit helps
save a lab freezer or temperature chamber's contents.....(design idea added 9/08) |
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Oscillating Output Improves System Security - 02/06/03 EDN-Design Ideas: (design idea
added 1/05) |
