Burglar-alarm

Posted on Dec 18, 2012

The single-chip, burglar -alarm circuit shown uses a dual 556 timer, draws 10 mA of standby current, and generates a pulsing alarm signal that conserves battery energy. Once activated, the alarm wilLremain on, independent of the subsequent state of any of the sensors. The sensors support both deferred and immediate-action modes. You can attach this circuit to your car`s internal lighting circuitry using a single wire and a relay. To arm this circuit, you open your car door and close switch SA. The switch discharges capacitor C4 and holds the timer (one half of the 556 !C) in a reset state to prevent false triggering while you`re arming the circuit. When you close your car door, the circuit enters a standby mode.

Click here to download the full size of the above Circuit.

If the door is then reopened, the sensors apply a negative-going pulse to trigger 1. Output 1 then increases, enabling the alarm for 1.1R1C1 seconds. Output 1 "s high state triggers the multivibrator, the other half of the 556, which begins to cycle after a delay equal to 1.1 (R2 + R3) C2 seconds. As long as the timer"s output stays high, the multivibrator will continue to cycle, turning the horn off and on at 3.3-second intervals. During the interval between time that the timer"s output increases and the time that the multivibrator"s output decreases, you can disarm this circuit using switch SA. To prevent false triggering caused by switch contacts, at S1, S2, and S3, that may bounce when closing the door, make the R6C3 time constant as large as possible. In addition, capacitors C1 and C2 should be tantalum types and should exhibit leakage of less than 1 11A at room temperature.

Leave Comment

characters left:

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Precise audio clipper

A differential amplifier makes an excellent audio clipper and can provide precise, symmetrical...

arduino model railway control

Model railway running under computer control using the laptop to send commands over the USB port...

TV cascades

Older TV sets that do not have a diode split flyback usually contain a flyback that gives about...

TDA2009 single power amplifier circuit diagram

Always wanted to do morning exercise machine, also suffering no single power can not find...

EPSON PHOTO 830U printer power circuit

EPSON PHOTO 830U printer power circuit It shows EPSON PHOT0 830U printer power supply circuit,...

A hydraulic circuit diagram showing

FIG circuit, the oil pressure sensor is converted into a variable resistor Rt. Due to changes in...