led music level indicator light circuit

Posted on Feb 5, 2014

The shown LEDs in the circuit sequentially light and `dance` as per the level of the music applied at the input, preferable directly from the speaker terminals of the audio gadgetwhosemusic level is to be monitored. The above stage is identical to all the LEDs included in the circuit for obtaining the desired push-pull effect in response to th

led music level indicator light circuit
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e applied music level at the input. If you see the circuit closely you will find that the the ground to the first transistor/LED stage from left comes across only a single diode, however the preceding stages ground potential has to encounter the extracorrespondingnumber of diodes in theor path. As we allknowthat a diode has thepropertyof dropping 0. 6 volts, means that the first transistor would conduct much sooner than the second, the second transistor conducts sooner than the third and so on. Because as the number of diodes increase in the path of therespectivetransistor, the conduction is inhibited until the the voltage sufficiently increases for bypassing the diodes overall forward voltage. This increase in voltage can happen only when the pitch of the music increases, giving rise to a sequentially running LED bar graph which shoots forward in response to the pitch or loudness o the applied input music. The transistor at the inputisa PNP and complements the rest of the transistors employed forilluminatingthe LEDs. The PNP transistor at the input amplifies the applied low level music sinal to levels which is just enough for illuminating the LEDs with reference to themusiclevels, .

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