Electronic_

Published:2009/7/19 23:11:00 Author:Jessie | From:SeekIC

With this circuit, the LM3909 oscillates at the speaker-cone free-air resonance point. That is, if the speaker is in an enclosure with a higher resonant frequency than the speaker, this becomes the frequency at which the circuit oscillates. An educational audio-demonstration device, or simply an enjoyable toy, has been fabricated as follows. A roughly cubical box of about 64 3 was made with one end able to slide in and out like a piston. The box was stiffened with thin layers of pressed wood, etc. Speakers, circuit, battery, and all were mounted on the sliding end, with the speaker facing out through a 21/4 hole. A tube was provided (21/2 long, 5/16 ID) to bleed air in and out as the piston was moved while not affecting resonant frequency. Minimum volume with the piston in was about 10 3. Slide tones can be generated, or a tune played, by properly positioning the piston part and working the push button. National Semiconductor Linear Applications Handbook 1911 p 401.



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