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-   -   Sound activated LED (http://www.hardwarecanucks.com/forum/cases/51845-sound-activated-led.html)

bigFOIG February 22, 2012 11:40 AM

Sound activated LED
 
Anyone know how I can acheive this? Basically I want LED's to flash with the music. Any ideas? I know there is a Sound Activated Cold Cathode kit, but I want to use my own LED's. Is it possible to use the sound activated circuit board and replace the cathodes with my own LED's?

krazyups February 22, 2012 12:53 PM

Yes, you can buy just the sound activated module and use your own LED's, just make sure you use a current limiting resistor to get the appropriate current draw and you should be good to go.

Silent_Avenger February 22, 2012 03:15 PM

Hrm if I remember my electronics correctly you'll need a TIP31(3A) transistor or TIP120(8A) transistor. Also an old molex(female) power connection, 3.5mm jack(will only use L or R signal not both) and splitter, solder iron, solder, flux, wire and your LEDs also preferably a DIY pcb board. I made a quick diagram instead of trying to explain it. I'd test it out somehow first like using an old set of speakers with a headphone jack and an old psu or power brick for power just in case you have something shorted out it won't harm you main system.

http://img268.imageshack.us/img268/9633/diagrame.png

Hope this helps.

KaptCrunch February 22, 2012 03:47 PM

make magizine light organ

bigFOIG February 22, 2012 03:54 PM

Quote:

Originally Posted by Silent_Avenger (Post 604723)
Hrm if I remember my electronics correctly you'll need a TIP31(3A) transistor or TIP120(8A) transistor. Also an old molex(female) power connection, 3.5mm jack and splitter, solder iron, solder, flux, wire and your LEDs also preferably a DIY pcb board. I made a quick diagram instead of trying to explain it. I'd test it out somehow first like using an old set of speakers with a headphone jack and an old psu or power brick for power just in case you have something shorted out it won't harm you main system.

http://img268.imageshack.us/img268/9633/diagrame.png

Hope this helps.

Oh, the geniuses on HWC. Looks simple enough for me to do. I actually heard about the TIP31 before and I forgot all about it. Thanks for this.

Silent_Avenger February 22, 2012 04:37 PM

I also forgot to mention you don't want to bridge the Left and Right wires together from the 3.5mm jack because it can short out your sound card. There are ways you can turn a stereo signal into a mono signal properly but it's just easier to use either the L or R signal from the 3.5mm jack. Also hardly a genius just a guy who liked to tinker with electronics when he was a kid.

ilya February 22, 2012 05:53 PM

It's not as easy as it looks but it's not hard either.

You'll probably also want separate circuits for multiple frequency bands or else you'll end up with a monotone light show. Depending on your source you'll also need a power conditioning circuit to go with it.

Silent_Avenger February 22, 2012 06:18 PM

Yea well I tried to do the most simple circuit possible it's easy to build on that. I assume it's wanted to go with the bass of any music/sound in which case should be able to add in a low-pass filter like so: http://sub.allaboutcircuits.com/images/02117.png
Image Source


Which should filter out any unwanted high frequencies. But like I said especially if it's your first time doing something like this get like an old radio or something you can test with so you aren't worried about killing your main pc because of a short or some other problem in the wiring.

Edit: Should also be able to go from 'Sub' output from an audio card but I've never tried it and never actually measured the output of the black sub connection on 7.1 channel audio so not 100% sure it would work properly.

krazyups February 22, 2012 07:09 PM

Just make sure that your input signal is such that you keep the transistor in linear mode. A Tip31 has an hfe of ~100 at low currents, so to get 20mA out for your LED's you only need 200ľA of input current, so you'll need to measure the maximum output of your sound card (voltage wise) and select an appropriate resistor so that you don't exceed that.

A good project, and good ideas from the HWC community!


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