LOW_LEVEL_SOUNDER

Published:2009/6/18 23:07:00 Author:May | From:SeekIC

This is a simple low-level noise maker that's ideally suited to certain alarm applications. When the sounder is Iocated in another part of the building, the sound level is loud enough to be heard, but is not loud enough to wam off an intruder. A single 2N3904 npntransistor is connected in a Hartley audio oscillator, with a 1 kΩ to 8-Ω tran-sistor-output transformer doing double duty.The circuit produces a single-frequency tone that can be varied in frequency by changing the value of either or both R1 and C1. Increasing the value of either component will Iower the output frequency and decreasing their values will raise the frequency. Don't go below 4.7 kΩ for R1 because you could easily destroy Q1.



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