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Metronomo with LM555
This circuit uses an LM555 to form a metronome. The metronome beats at a rate of 30 to 120 beats a minute. The beat rate can be set by adjusting potentiometer R3, and the beat level can be set by adjusting potentiometer R4. When the output switches high, C1 charges rapidly through diode D1 and resistor R1 in series to generate a beat pulse only a few milliseconds long. When the output switches low again, C1 discharges through potentiometer R3 and resistor R2 in series to provide an off period of up to two seconds (30 beats per minute). The output is fed to the speaker through level control R4 and buffer transistor Q1.