Whistle Responder Schematic


Posted on Feb 7, 2014

Some 20 years ago it was common to see small key-holders emitting an intermittent beep for a couple of seconds after its owner whistled. These devices contained a special purpose IC and therefore were not suited to home construction. The present circuit is designed around a general purpose hex-inverter CMos IC and, using miniature components and b


Whistle Responder Schematic
Click here to download the full size of the above Circuit.

utton clock-type batteries can be enclosed in a matchbox. It is primarily a gadget, but everyone will be able to find suitable applications. This device beeps intermittently for about two seconds when a person in a range of around 10 meters emits a whistle. The first two inverters contained in IC1 are used as audio amplifiers. IC1A amplifies consistently the signal picked-up by the small electret-microphone and IC1B acts as a band-pass filter, its frequency being centered at about 1. 8KHz. The filter is required in order to select a specific frequency, the whistle`s one, stopping other frequencies that would cause undesired beeper operation. IC1C is wired as a Schmitt trigger, squaring the incoming audio signal. IC1D is a 2 second-delay monostable driving the astable formed by IC1E & IC1F. This oscillator generates a 3 to 5Hz square wave feeding Q1 and BZ1, thus providing intermittent beeper operation.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Capacitor discharge ignition system ( PIC 16F615 )
    Positive-peak-detector
    Light-controlled-lamp-switch
    Water level controller using 8051
    transistors Problems with Wien Bridge oscillator circuit simulation in Mutisim
    photo sensor control relay
    headlights 1967 and 1958 Cadillac Eldorado
    Darkroom Timer v2.0A for PCB Exposure Box
    DIY Color Densitometer
    Complete SS Laser Power Supply Schematics
    Thyristor controlled motor reversing circuit a timer



    Top