This device beeps intermittently for approx. two seconds when a person in a range of about 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's operation. IC1C is wired as a Schmitt trigger, squaring the incoming audio signal. IC1D is a 2 second (approx.) 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's operation.
Power supply range: 2.6 to 3.6 Volts.
Standing current: 150΅A.
Depending on dimensions of your box, you can choose from a wide variety of battery types:
2 x 1.5 V batteries type: AA, AAA, AAAA, button clock-type, photo-camera type & others.
2 x 1.4 V mercury batteries, button clock-type.
1 x 3 V or 1 x 3.6 V Lithium cells.
Instead of the buzzer drive the motors, connect the inputs of an L293D inplace of BZ1 and thats it , it can move with u r voice , but u cant make it drive right or left.
If u want more help , plz ask me .