LED Music Level Indicator Circuit Diagram

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 gadget whose music level is to be monitored.
The proposed LED music level indicator circuit may be understood as follows:

The components which support the LED illumination are the associated NPN transistor, the emitter resistor, the base preset and the corresponding diode.
The above stage is identical to all the LEDs included in the circuit for obtaining the desired push-pull effect in response to the applied music level at the input.
However there's one difference between the LED stages, though most of the component placement is similar, the diodes form a different pattern.
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 extra corresponding number of diodes in theor path.

As we all know that a diode has the property of 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 the respective transistor, 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 input is a PNP and complements the rest of the transistors employed for illuminating the 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 the music levels,.

Parts List for the explained LED music level indicator circuit

All NPN Transistors are BC547,
PNP Transistor is BC557,
All Presets are 10K,
All resistors are 100Ohm,
LEDs as per choice

                                                                                          

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30 comments

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January 23, 2012 at 4:13 PM delete

thanks, it works very well

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Anonymous
July 29, 2012 at 8:04 PM delete

Did u try this practically? Pls let me know.....

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July 29, 2012 at 9:50 PM delete

Yes i tried it long ago and it worked, I think you too have made it successfully, you said it in the previous comment above.

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Anonymous
January 29, 2013 at 5:55 PM delete

sir,, what is the use of the capacitor in the circuit? can i remove it?

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January 29, 2013 at 8:15 PM delete

it's for isolating the transistor from DC potentials....

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Anonymous
February 15, 2013 at 7:45 AM delete

is it lit altogether? or by peak?

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March 1, 2013 at 8:21 PM delete

quick question, does it work like an equalizer?

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March 1, 2013 at 8:26 PM delete

follow up question, can you show me the diode that you used. .

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March 1, 2013 at 9:49 PM delete

it's 1N4148, you can check out its datasheet for the spces....

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March 9, 2013 at 6:30 PM delete

so this circuit is like a blinker?do you have a circuit for equalizer using transistor?

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March 9, 2013 at 8:39 PM delete

i didn't understand when you said "equalizer" type....it's not a blinker type it's a sequential type, and will move to and fro with music peaks.

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Anonymous
March 10, 2013 at 3:17 PM delete

sir i tried this circuit but it is only blinking ?

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March 10, 2013 at 6:23 PM delete

sorry, i mean for the equalizer is like an spectrum analyzer using transistor only. is it possible sir?

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March 10, 2013 at 9:19 PM delete

what is happening with your circuit??

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March 11, 2013 at 1:37 PM delete

you will have to make many such circuits and arrange each LED channel like bars.....

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March 11, 2013 at 5:00 PM delete

can you make a circuit of that sir?without using an IC?

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March 12, 2013 at 9:16 AM delete

I'll try it out sometime later and post it.

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March 12, 2013 at 4:20 PM delete

thank you sir, i am badly needed it.

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October 8, 2013 at 6:50 AM delete

Sir Swagatam, Can I add this circuit from 5 LED's,transistors and diode's Into 10..

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October 8, 2013 at 1:09 PM delete

Hi Jenson, yes you can do it.

For more efficient results you can try the IC LM3915 circuit as given here:

http://homemadecircuitsandschematics.blogspot.in/2012/03/how-to-make-simple-vu-meter-circuit-at.html

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December 19, 2013 at 7:29 AM delete

Sir Swagatam, Can I use a tip42 at the input section instead a small power general purpose pnp?

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December 19, 2013 at 9:49 PM delete

sorry tip142 will not give proper results

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August 24, 2014 at 8:20 PM delete

Can i replace the diodes by 1N4007

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March 1, 2016 at 11:51 AM delete

hello engr..please how can i get the circuit, i cant find the circuiut

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April 25, 2016 at 6:04 PM delete

Hi engineer, if I don't want to connect speaker, can I use voltage? I want to construct this circuit in multisim and do simulation, but I don't what can I put for the speaker component.

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April 26, 2016 at 7:32 AM delete

Hi Sharon, sorry I did not understand your question, how can you replace the speaker with a voltage??

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