warning alarm circuit schematic

Warning Alarm Circuit with CD4001

Unorthodox warning alarm circuit presented here is infact a single chip based general purpose sounder, which produces a pulsed alert tone when its input receives a valid trigger signal. The circuit can be easily interfaced with a number of electronic gadgets and sensors and it requires only 12V dc supply input for proper working. A positive level input at trigger point (J1) activates the warning alarm unit.

At the heart of the circuit is a popular quad – two input NOR gate IC CD4001, here wired as two independent gated astable multivibrators. Initially, in standby mode, T1 is off and the tone generators are inactive. When T1 is enabled by a proper +ve level trigger signal, pin 1 of CD4001 is pulled low through switching diode D1 first astable block enters in active mode and then activates the second astable block, which is configured as an acoustic alarm. A large piezo-ceramic element (acoustic transducer) at the output of (pin 11) CD4001 will give superb results.

Warning Alarm Circuit Schematic

warning alarm circuit schematic


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  • zainahmedsharif2705gmail-com

    thanks for the schematic man.
    I want to use this circuit in my project
    I just want to ask what type of input signal does this alarm requires? so that I can modify the circuit to integrate it within my cricut. Thanks alot

    • T.K.Hareendran

      As indicated in the article, any proper +ve level signal can be used. For example you can feed a logic-high level (H) signal from an external device to trigger the alarm. Take note, you must add suitable resistor (usually a 1-10 Kilo Ohm) between the external device and input of J1.

  • affifa

    Hello sir ,
    I want to take mobile bug as mini project .I want all details about this project with pcb lay out on my this email address.I have read about sealed maintainance free battery in LED Searchlight circuit how much cost of this battery and i want all details about this project on this email address please send me all details.It’s urgent.

  • selva

    how to use it . and what purpose is it.

    • T.K.Hareendran

      Now a days,readymade and pre-configured sensor modules are widely available.Often they offer an active high or active low level signal at their output(s).PIR sensor is a good example.You can connect this alarm at the output to complete the construction.Refer my circuit Vibration sensor/detector and try to interface this with the detector.

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