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LEDs on sound

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WG1337

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Hi!
I have been thinking about this project that makes LED lights blink at the rythm of the music. If I understand these things right then I can do this by adding LEDs to a speaker, on a wire before the wire reaches the actual speaker part. Before I "destroyed" my speaker I wanted to try it with some headphones, but didn't work, but thats probably because of the low voltage. I have at home speakers that uses wires outside the speaker (like most home theaters) so I added the LED there, but nothing. What I'm doing wrong?
 
A speaker uses AC voltages of about 24VAC or more in a home sound system.

A red LED uses a DC voltage of about 2VDC and a blue LED uses a DC voltage of about 3.5VDC. Ordinary LEDs are operated at 25mA. More than 30mA will burn them out.
The max allowed reverse voltage for an LED is only 5V.

You probably didn't use a current-limiting resistor and you probably didn't use a rectifier so your LED instantly burned out.
 
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I would consider adding a current-limiting resitor when it will go to a good speaker, now I'm just testing and I didn't burn them out.
Used a battery that has 12V, they still worked. How much does a ordinary headphone have voltage? Btw, could skip a resistor by adding many LEDs :)
 
An audio amplifier has a current output of many Amps.
An ordinary LED will burn out if it is fed over 30mA which is only 0.03A. So you must use a current-limiting resistor. The LED does not hurt the speaker, the amplifier's current hurts the LED.

An audio amplifier has a voltage that is much higher than the 5V max allowed reverse voltage for an LED. So a rectifier must be used.

The output from a headphones jack is maybe only 1V which is not enough to light an LED.

If you connect an LED directly to a 12V battery without a current-limiting resistor then it will instantly burn out.

Many LEDs can be connected in series and in series with a current-limiting resistor. But the voltage will need to be high enough.

LEDs in parallel don't work because each one has a slightly different voltage. The LED with the lowest voltage will hog all the current then it will instantly burn out, then the next, then the next.
 
Oh, I see.
Well thanks for the info.

But are you sure that parallel won't work?
I think you ment the other type, because I added 2 LEDs in parallel and they seemed to shine like only one LED.
And as I remeber in school - in parallel voltage is the same.
 
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Yes, things in parallel use the same voltage. But LEDs are not exactly the same. One might be 2V and another might be 2.2V. The 2V one will hog all the current and it will burn out.

Some LED flashlights have their LEDs in parallel. But the LEDs are tested, sorted and matched.
 
Leds on sound = VU meter or Light organ in my opinion

lot's of schematics availible on the net

Robert-Jan
 
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