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SCR Based Burglar Alarm: (electronic design added 6/07) |
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Security Alarm: (electronic circuit added 1/03) |
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Seismic Alarm: My original "Deer Repellent/ Seismic Sensor" recommended using a speaker with a weight glued to the cone as a
vibration sensor (see bottom of page) but it recently occurred to me that the speaker could supply the mass itself. By gluing a standoff to the center of the cone, an inexpensive 2", 8 ohm
speaker becomes a vibration sensor with a natural resonance below 100Hz which is quite good. My... (electronic design added (6/07) |
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Simple Alarm System: (diagram added 6/03) |
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Simple Door Alarm Circuit: This is a simple - easy to build - alarm circuit. For power - I used a small 9-volt battery. But the circuit itself will work from 5 to 15-volts - just choose
a buzzer that's suitable for the voltage...(added 05/07) |
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Simple Electronic Buzzer: This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555
timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can be changed by varying the 10K
resistor. (added 10/05) |
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Simple Fire-Door Alarm Circuit: This is a simple - easy to build - alarm circuit. For power - I used a small 9-volt battery. But the circuit itself will work from 5 to 15-volts - just
choose a buzzer that's suitable for the voltage...(added 05/07) |
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Single Button Lock Provides High Security: 03/04/99 EDN-Design Ideas / (added 11/05) Figure 1 is the block diagram of an
easily programmed, single-button combination lock. You operate the lock by using a series of short and long pulses from a momentary switch that masquerades as a doorbell button. The circuit
uses inexpensive CMOS logic. The retriggerable timer, T1, locks out entries made after the.... |
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Single Zone Alarm: (diagram added 6/03) |
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Snore Alarm: The idea behind this snore alarm, is just to rouse the snorer, not the entire household. To wake the sleeper,
vibration is used, not an audible alert. The vibration is provided by a small motor housed in a small 35mm film case, which can be placed under the sleepers mattress or pillow. This circuit
has a level control and peak display indicator, a variable trigger threshold and trigger indication. (added 10/05) |
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Speed
Limit Alarm: (circuit added 9/04) |
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Speed-limit Alert: (electronic design added 6/07) |
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Sun-Up Alarm: The Sun-Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark
area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor is very sensitive to light. (Any
phototransistor will work fine) The sun shining on this device will provide a .... (added 09/05) |
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Theft Preventer Alarm: This circuit utilizing a 555 timer IC can be used as an alarm system to prevent the theft of your
luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken. The circuit is straightforward. It uses a 555 IC wired as an astable
multivibrator to produce a tone of frequency of about 1kHz which .... (added 10/05) |
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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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Tiny Two Zone Alarm: (electronic circuit added 1/03) |
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Touch Activated Alarm uoguelph_: (schematic / circuit added 10/02) |
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Ultrasonic
Remote Control and Alarm: (circuit added 7/02) |
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Wailing Alarm: (schematic / circuit added 10/02) |
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Water Activated Alarm circuitsdb: The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current
of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. However...(added 05/07) |
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Water Activated Alarm: (diagram added 6/03) |
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Water Activated Alarm: (electronic design added 6/07) |
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Water Level Alarm: (electronic design added 6/07) |
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Water Level Alarm: (schematic added 9/02) |
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Water Level Controller: (electronic Circuit / Schematic added 10/04) |
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Water Level Indicator with Alarm #2: Here is a simple, versatile circuit which indicates the level of water in a tank. This
circuit produces alarm when water level is below the lowest level L1 and also when water just touches the highest level L12. The circuit is .... (added 10/04) |
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Water Level Indicator with Alarm: This circuit not only indicates the amount of water present in the overhead tank but also
gives an alarm when the tank is full. The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs. When the water is empty the wires in the
tank are open circuited and the 180K resistors pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the tank connected.... (added
10/05) |
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Water-level Alert: Beeper or flashing LED alert. (electronic design added 6/07) |
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Wire Loop Alarm: (circuit added 7/02) |