Sound-activated LEDs

[Nagoshi]

I know I did post this a while ago, but it seems like we cleaned the forums and it was supressed, and Im decided to do it but I need tips. Might as well post it there in the case someone else is wanting to do it. Ive got two circuits types that are said to working. Here are the links.

http://www.ovelha.org/pasteler0/2005/12/06/howto-blinking-leds/
This one is using a TIP31, but is said to get fautly and won't blink after a while.

http://www.runtimeerror.net/blinky/index.html
This one uses resistors and a 9V battery as power supply.

Which one would you recommend, I dont mind getting the components since I know a guy who can get about anything for cheap.

As I said, some people are complaining (in the comment section) about the TIP31 not working after a while, and the resistor scheme (second link) seems to work better (by looking at the video) but I don't like the 9V battery. If possible, Id use power from a 5/12V Molex, or 5V from the USB (cause I might be doing a project with my USB memory stick, look in the mod help section).

Basically, Id build a pair of one of these circuits, each one built on a separate channel (one left, one right) so I will have the best visual effect. But Im currenly trying to find a way to perfect them. The resistor scheme would be perfect, if combined to a molex or USB, is there a way to do it? And would it works as well as on the 9V battery? Thanks!

[Dilphat]

nagoshi, did you get it to work right? and which choice did you pick?

[Brockgrimes]

Take a Pyle LED Sound Activated Light Rod, apart and remove the car 12v adapter and just hook it straight to a molex connector. If you take it apart you can use the LED in the front of the case for the power light, it'll blink or fade and color change.

http://www.pricegrabber.com/user_sales_getprod.php?masterid=62929258&lot_id=8641198

http://cdn.overstock.com/images/products/P11115942.jpg

[Aud1073cH]

I came across a very simple circuit in a toy megaphone that flashes LEDs with the sound.

The toy used a basic audio amp (LM386N) for amplification, and took another lead off of the output to the base of a transistor that drove the LEDs.

The LM386N-4 will run on a voltage range of 5-18V (most run on 4-12V) I'd use the -4 version and run it with the 12V. the others should run OK on 5V or better, 7V (the difference between your 5V and 12V rails)

If you tap inline with your soundcard, you may not need the amp, just the transistor to buffer to switch the LED.