sound reactive led mod help

[Sesheron]

so I saw a fun mod for computer speakers today and decided to do it.

basically you take the power led and move the leads to the speaker.
effectively it becomes a sound reactive led.

but my problem is, the led wont turn "on" except when the volume is way more than comfortably loud.

if the problem was in reverse and the led was always on I know I could just do a resistor in series. but that isn't the issue.

any ideas?

 

[Thor]

speakers dont run off a constant voltage, and leds need a voltage above X.x volts (depends on the led) befor they will fire, your speakers will handle x watts max, but at a normal listening level you make only be produceing a small fraction of that (logitech x540s for example, the sats omly have a max rateing of 7 watts i beleave it was.. and they can get pretty damn loud considering...

any way, speakers are driven more off curent than voltage and as a*v=w, your amp isnt produceing the voltage needed untill the volume is skyhigh.

 

[Mohonri]

Yeah, it appears you aren't getting enough voltage to your speakers to light up the LED often enough. What you'll need is a simple opamp circuit that will amplify the signal just enough to light your LED when appropriate. Use either the inverting or non-inverting (it doesn't matter) circuit from this page. Conveniently enough, for this particular application, you won't need to add any isolating capacitors, or create a bipolar power supply. Just hook up the negative power supply pin from the opamp to ground and the positive power supply pin to some voltage source.

 

[Sesheron]

Hmm. Thanks. I agree. The opamp circuit would work quite well. I am in my third year of college as an electrical engineering degree. I have done stuff like this, but not often enough for me to remember to "use" it in everyday projects yet. Its kinda like one of those "doh, i am an idiot situations"

Now for the hard part. Finding time to stop by an electronics store. ::sigh::

Thanks for the advice guys.