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Category: Security Circuits / Alarm Circuits This circuit is also crossed to: 555 Timer Circuits Views: 2285 Rank: 0 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. To set the alarm, open S2 ( it is normally closed ) this will give you about 5 seconds to get out and close the door. The exit delay time is set by R1 and C1. If anyone opens the doors for more then two seconds the horn will sound until power is removed from the circuit. The 2 second time is set by R2 and C2. If you open the door, you must deactivate the alarm by closing S2. This very basic circuit could be used for a home also. visit page.
Related circuits This circuit sends out a loud tone if the input switch (S2) is not retriggered at preset intervals. This switch will suit the Modular Burglar Alarm circuit. However, it also has other applications. The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13 terminals. The matrix type with 7 terminals will NOT do. Choose the five keys... 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. ELECTRIC FIELD DISTURBANCE MONITOR II This schematic is the power supply and front-end sections of the field monitor that is discussed in more detail at Electric Field Disturbance Monitor. The system can detect human and animal motion by the electric fields they disturb. When the protective circuit is interrupted (opened), the alarm sounds The circuit has two ranges: 10 sees to 5 mins and 1 min to 80 mins. It can be powered by a 9-V battery. With the LED connected as shown a reasonable frequency of flashing occurs throughout the range of operation. In the circuit, U1 amplifies the audio picked up by the condenser microphone. Resistor Rl limits current, while R2 and R3 center the output of the amplifier to %B+ to allow a single-ended supply to be used. Diodes D1 and D2 rectify the output of Ul, and C3 filters the resulting pulsing dc. Thus,... This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This causes the resistance of LDR to increase and the voltage at the base of the...
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This is a burglar alarm for cars.If some one opened the car door.The alarm will activate.Normally this circuit provides 5 second to open the door and close it but If somebody opened it more than that the alarm will activate.
How to Install Electric Bells, Annunciators, and Alarms: Including Batteries, Wires and Wiring, Circuits, Pushes, Bells, Burglar Alarms, High and Low ... and the Location and Remedying of Troubles book download Norman ...
This long-range cordless burglar alarm circuit makes use of a cordless telephone (CLT) unit with paging facility and a few low-cost discrete components. The circuit is so simple that even a novice can easily construct it without ...
The following article discusses a few very simple intrusion detector circuits, or simply burglar alarm circuits. The presented designs are simple yet extremely effective with the functions. A burglar alarm basically consists of a ...
In this figure is design circuit for modular burglar alarm circuit. 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 ...
Protect your Room with your own Laser Security System!!!
Alarming Switches
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