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Sound to light for a noob

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MystX

New Member
Hi everyone, my first post so bare with me.

Im looking at making a simple 'light pulses to music' circuit for my PC which powers around 10 LEDs and 1-2 cold cathode tubes. The problem is that im new to electronics and have no idea how to do this (id like the lights to get brighter as the sound got louder, rather than just an on/off situation). The input would be a 3.5mm headphone jack.
I know the neons will be more difficult as they run off an inverter, but any ideas?

Thanks in advance
 

microtexan

New Member
Google "Color Organ" and see if any of the circuits might do what you want.
 

wuchy143

Member
You could hook take the music signal and connect it up to a few filters. Music is from 0-20k so for example you have two filters. One is responsible for for 0-10k and the other is responsible for 10k-20k. So the first filter will only produce an output if there is enough energy in the low frequencies. The second filter will produce and output from 10k-20k. You will want to hook up the filters to some sort of switch(transistor...relay...to name a few) which can turn on the LED"s.

I did a project like this a few years ago when I was learning(still am :) ) and used 7 filters finely tuned to a specific frequency range. They were hooked up to a relay which turned on a set of xmas lights. Kinda cool. The lights literally danced with the music. All it took was a few opamps, r's, and c's.
 

MystX

New Member
Thanks wuchy143, but rather than have the lights either on or off, id like them to get brighter or dimmer depending on the volume of the music. And they can pulse at the same time. Im not looking for ones that do different things.
 

Sceadwian

Banned
And what information have you come up using Google?
 

MystX

New Member
No mike. As outlined in my previous posts, all the LEDs will pulse the same - they will all be wired in parallel to one source, if you will.
And what i want is rather a lot simpler to those things you posted. Im just looking for music gets louder -> lights get brighter.

EDIT:
Basically, i want the opposite of this-> http://www.youtube.com/watch?v=8xAg9PlLs7k
 
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MystX

New Member
Thanks Mike,I know how to use google.
But the search you suggested renders nothing of what i want, but heaps of on/off sound activated lights.

And the diagram you suppied is for mains power. Whereas this will be running off either 5 or 12 volts. Any difference between the two circuits?
 

MystX

New Member
Back again,

Me and an electronics teacher managed to come up with this simple circuit which powered 1 LED (i thought the drawing was great). This effectively does what i want it to, but i would also like to have the LEDs dimly lit when there is no sound. Is there a way i can do this by applying a small source of power to the LED itself that the power from the trasistor will just suppliment? Maybe something like this?
 

audioguru

Well-Known Member
Most Helpful Member
Your second circuit has the transistor as an emitter-follower so it needs a high signal level to light the LED.

Your first circuit needs a base resistor. A second resistor can be added to light the LED dimly when there is no music.
 

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MystX

New Member
Ah, thanks audioguru. I was basically guessing with that second one. What effect will putting more LEDs in parallel to the first one have?
 

audioguru

Well-Known Member
Most Helpful Member
LEDs in parallel do not share the current evenly unless you buy hundreds, test each one and match them. Since they do not share evenly then one will be very bright and will soon burn out, then the next bright one will burn out.

Each LED should have its own current-limiting resistor or you can connect a few LEDs in series with one current-limiting resistor and a higher supply voltage.

The max allowed collector current for the BC547 transistor is only 100mA which is only 4 bright LEDs in parallel.
 
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