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It really doesn’t get any more than simple than this, hook up a LED to some speakers, crank it up and watch the blinky – Link.

Phillip Torrone

Editor at large – Make magazine. Creative director – Adafruit Industries, contributing editor – Popular Science. Previously: Founded – Hack-a-Day, how-to editor – Engadget, Director of product development – Fallon Worldwide, Technology Director – Braincraft.


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Comments

  1. Robin Matuk http://robinmatuk.typepad.com/ says:

    Wow. Interesting site. No doubt a springboard for many a business idea, including your own.

  2. The Oracle says:

    The LED will put a non-linear load on the audio signal, distorting the sound.

    The correct way to do this would be with a high-impedence interface. There must be at least a thousand cheap and simple kits on the web that do it right.

  3. Michael Una says:

    Ha! I just exhibited this past weekend an audio-based sculpture employing this very technique, using an 8-channel sound system to drive paper lanterns with speakers and an array of LEDs inside: http://www.vimeo.com/624373

    There’s a semi-documentary video regarding my build process here: http://www.youtube.com/watch?v=BNSCvJ91Bxc

  4. Guyfrom7up says:

    I’m on Make!

    As for the non-linear load thing, I didn’t notice a difference in the sound quality. If you hooked up a bunch of leds, I could see a problem (and i’ll adress that in my instructable, thankyou!). But if one was to do that it could be solved with a diode, and a transistor.

  5. shecky says:

    I remember doing this years ago when playing around with stuff. By the book, LEDs used in such a way should cause some kind of distortion. However, it was inaudible with that particular gear used. It’s always been a bit of a puzzler with me. All I can think of is that the voltage swings at the speaker were simply not large enough for the LEDs to clip hard. And my guess is that the current demands of the LEDs were not enough to significantly alter the performance of the power amp, relative to driving a loudspeaker.

  6. Matt says:

    I think the distortion might not be apparent maybe because the LED only seems to be driven into conduction on low frequency transients, where the momentary clipping would be less noticeable?

  7. The Oracle says:

    Guyfrom7up. There’s so many things wrong with what you said and you clearly revel in your ignorance so I won’t waste my time pointing them out.

    Your electronics knowledge is dangerously lacking. I can only hope you never play with anything high powered or Make might get a link from the Darwin Awards.

  8. Matt says:

    The Oracle – instead of being a pedantic jerk, maybe you could explain where he’s going wrong? A diode and a transistor could certainly be part of the solution to the loading problem, if used as a half wave rectifier for the audio signal and the transistor as part of a high impedance buffer. My guess,however, is that you’re not really interested in the poster’s safety or experience, you just get a kick out of belittling people.

  9. macegr says:

    Matt and The Oracle…hey, I also like to laugh at silly and/or incorrect methods of doing something, such as the hack under discussion. But at the same time, I like doing silly and/or incorrect things, take today for example: (http://www.flickr.com/photos/macetech/2215680810/in/pool-make/). Guyfrom7up is not pretending to know a lot about electronics, and just by tinkering around he found pretty much the simplest way to have a light react to music. No one learns anything new by sticking to only what they know. Both of you…just lighten up, we all have EE degrees but this isn’t the forum to sling theory around.

  10. terraplop says:

    An interesting 2nd video would be the puff of smoke coming our the vents of
    a “bricked” $1500 Bose amp.

  11. The Oracle says:

    Matt, I did try and give a useful response in my first post on the thread. I got his idiotic response instead.

    A diode and transistor could certainly be part of a solution but the way I throws the parts out there, it doesn’t give the impression he knows what he’s talking about. Pick any 2 random basic components. I’m sure any half-decent hobbiest could come up with a solution that involves them. As you say, the transistor can be part of a high impedence buffer, but only with a resistor which the original poster makes no mention of. I think he’s just throwing random parts out there to pretend.

    Compare the tone of my 2 previous reponses, originally I was interested in helping, but after his reply, yeah, I wanted to give him the belittling he needs. Just because he didn’t notice a difference on low quality speakers when he wasn’t even listening for a difference, he takes that to be an authoratative test.

    7up, let me try to help then. In *theory*, when the amplitude of the audio signal is below the Vf of the LED, the LED is off and it’s as if the LED wasn’t there as far as the signal is concerned. When it’s above the Vf, the LED is on, and you are dropping the signal. So as it flickers, you’re making a huge difference to the audio signal.

    In *practice* the LED does not behave as an ideal diode does in theory and there are shade of grey. But the general effect is there and you’re chopping the louder parts and not doing much to the quieter ones.

    If you don’t hear this, it’s because you weren’t listening for it and were more interested in watching the light flicker than listening to the effect.

  12. José Ferreira says:

    Use and impedance transformer from 8 or 4 ohm to 200ohm and you are there you can even make a small amplifier from a tda or a tea ic to feed the impedance transformer :)

  13. Ryan says:

    The Oracle, I find you post this morning much more informative then the first two. You have to remember most people in this wonderful either space called the internet do NOT have EE degrees. In fact few have even had one high school class on electronics. So if you find someone that has the curiosity to explore however misguided then one should point out not only what is wrong but in small quick detail why it works and why it is wrong. It seems to me that for a first principle fact finding experiment this was well done. In fact I had a girlfriend in high school that has a line of eight or ten LED’s stuck into an IC tube that had been wired by an ex-boyfriend to act like a simple power level indicator. She told me it worked great until one time she had a party and turned up the volume too high and “the lightbulbs must have burnt out”

  14. The Oracle says:

    Ryan, you’re right, and thanks.

    As I tried to say it’s just that his reply to my first post came off as sounding like he knows best and doesn’t care to learn.

  15. shecky says:

    If you don’t hear this, it’s because you weren’t listening for it and were more interested in watching the light flicker than listening to the effect.

    Can you be any more condescending, Oracle? My experience was similar to Guyfrom7up’s. No noticeable distortion. I must not have been listening, too?

    As I tried to say it’s just that his reply to my first post came off as sounding like he knows best and doesn’t care to learn.

    That’ll explain why you came off sounding like a jerk. I guess.

  16. The Oracle says:

    Better to come of sound like a jerk than sounding as an idiot like you do, shecky.

  17. Guyfrom7up says:

    Ok Oracle, First off, I have a good amount of electronic knowledge. Have you even looked at my instructable or who I am? I give good, working advice to people on forms, and “in theory” you should actually look at what other stuff the person does before judging. answering all of your stuff:

    A diode and a transistor are the main parts. In my instructable I also included 2 resistors in the schematic for hooking it up with a transistor. I did all of this without reading your comments, and I’m only responding because I feel like my reputation’s being hurt.

    Low quality speakers? Those were altec lancing speakers, decent quality. I didn’t do it on really high quality speakers because I can’t afford really high quality speakers, I’m only 13.

    Yes, I already adressed that it causes a slight difference in sound, but not enough to be detectable to the ear. I’ve tested it many times with LED on and off, and I can’t notice a difference at all. The music for my test was extremeley highquality (320 kbps).

    Thankyou everybody else for defending me

    oh and if you don’t respond to this I’ll assume that you’re critizing other people for no reason.

  18. Matt says:

    We need Forrest Mims III to come in here and lay the smackdown. In any case, his circuit scrapbook has a great circuit for a color organ amongst many other things:

    http://www.textbookx.com/product_detail.php?upc=9781878707482&type=book&affiliate=froogle

  19. Digital Dad says:

    If you liked this and it did not short out your amp.
    You will love
    “Motor Speaker” by Guyfrom7up
    http://www.instructables.com/id/Motor-Speaker/

  20. The Oracle says:

    I guess I’ll have to respond so you don’t think I’m “critizing” other people for no reason. I would have let it go because I really don’t want to discourage you and what you’re doing is good for you.

    When I was a kid I did these sorts of experiments too. I didn’t post them like they were some revolutionary ideas.

    You are so quick in your instructables to post that you have no idea how something works, yet you are completely unwilling to listen to anybody’s explaination. That is repeated time after time in all your instructable’s comments sections.

    When you say you have a good amount of of electronics knowledge, you have no clue how deep that well goes.
    You’re using an LED and trying to say you know best how it works, of course you must know that it’s a p-n junction, and what that means, as well as what the depletion zone is, and how it’s width changes as current flows through it, and just why this change in width will distort your sound.

    I just did have a little look at some of your instructables. It’s probably good for you to learn but why do you feel the need to post it? How about your alcohol burner. You call it a substitute for for a bunsen burner. Let’s see, the ‘magic’ of a bunsen burner is the way it mixes the fuel with air to make combustion more efficient and the flame hotter. Your flame is much too cold, and what you’ve made is an oil lamp that for some reason you’re fueling with alcohol. Effectively you have a candle.

    Your free energy one is funny too. You repeat all over that you don’t know why it works but you insist it does. You don’t even know how you’re measuring the voltage of the capacitor because you don’t know how your multimeter works, yet again you insist you know better than the posters who reply. By the way, I’d suggest you look up Einstein’s photoelectric effect. If anything, your foil plate should discharge the capacitor when it’s struck by light. When are you going to get to using a coil of wire in proximity to an AC power line as a source of “free” energy?

    Not that it effects anything, but calling 320 kbps mp3′s extremely high quality is silly. It may take twice as much space to store but it’s not twice as much sound. Do a little research into psychoacoustic modeling.

    I could go on, but you’ve demonstrated you’re unwilling to learn anything, so what is it you are trying to accomplish by posting here?

    Keep experimenting and trying to teach yourself new things. But why do you feel the need to post every little thing on the internet? In 10 years, go back and read what you wrote here.

  21. guyfrom7up says:

    I always take into consideration to what people comment, and I improve the design. The free energy thing DOES work, but I don’t know why, and I felt like posting it because people might IMPROVE upon it.

    also I thank you for looking at my instructables

    Why do I post stuff? To show other what I make and how they can make it. It’s the instructables old motto. Now it’s the world’s biggest show and tell, I’m showing people what I make. It’s similar to say, why do you help people on forums, you arn’t benifiting. Your just a mean old crustly old guy.

    I know how leds work and I already said it’ll slightly distort the sound, why arn’t you listening? I just said that in my expierence i couldn’t notice a different. The distortion will be noticed much more when you add more leds!

    320kbps sounds better, compare it to normal cd quality.

    I’m not posting my stuff as if they’re revolutionary ideas, just to give other people ideas.

    I feel like we just got off to the wrong foot.

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  25. commodore says:

    WHAT ARE YOU TALKING ABOUT ORACLE??? THE guyfrom7up knows electronic well. HE helped me whit my electronic problem and I whit right say that he is very close whit this field.

  26. Daniel Andrade says:

    I have a similar project on my website: http://www.danielandrade.net/2005/12/06/howto-blinking-leds/

  27. WangChung says:

    The ORacle is a Pole smoker for sure!!!

  28. Joe says:

    I <3 gorillaz

  29. Anonymous says:

    Those speakers look like they probably run at about 10%THD anyway! You’re not going to notice the difference in quality at all