SINGLE_CHIP_MELODY_GENERATOR

Published:2009/7/10 2:13:00 Author:May | From:SeekIC

This melody generator, based on a 4093 CM0S Schmitt trigger, can be used in alarms, doorbells, and cars (audible reverse gear or lights-on indicator).Three of the four NAND gates in the 4093 are connected in series by RC networks. Oscillation is affected by feedback of the output signal of N4 to the input of N2. The logic-high levels produced by the cascaded gates in the oscillator circuit are used to bias one of associated diodes D1, D2, or D3). The relevant diode connects one of the frequency-determining capacitors (C1 through C3) to tone oscillator N1. The audio signal available when S1 is pressed is applied to complementary transistor pair (T1/T2) that drives the loudspeaker. The frequency of the emitted tone can be adjusted to individual taste with preset P1.



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