The Butt Lamp: Light From Where the Sun Don’t Shine


[Trent] is one of those guys who can make things happen. A friend of his gifted him a  mannequin derriere simply because he knew [Trent] would do something fun with it. “Something fun” turned out to be sound reactive LED butt. At first blush, this sounds like just another light organ. This butt has a few tricks up its …. sleeve which warrant a closer look. The light comes from some off the shelf 5050 style RGB LED strip. The controller is [Trent's] own design. He started with the ever popular MSGEQ7 7 Band Graphic Equalizer Display Filter, a chip we’ve seen before. The MSGEQ7 performs all the band filtering and outputs 7 analog levels corresponding to the amplitude of the input signal in that band. The outputs are fed into an ATTiny84, which drives the RGB strip through transistors.

The ATTiny84 isn’t just running a PWM loop. At startup, it takes 10 samples from each frequency band. The 10 samples are then averaged, and used to create a noise filter. The noise filter helps to remove any ambient sound or distortions created by the microphone. Each band is then averaged and peak detected. The difference between the peak and the noise is the dynamic range for that band. The ATTiny84 remaps each analog sample to be an 8 bit value fitting within that dynamic range. The last step is to translate  the remapped signal values through a gamma lookup table. The gamma table was created to make the bright and dark colors stand out even more. [Trent] says the net result is that snare and kick drum sounds really pop compared to the rest of the music.

Without making this lamp the butt of too many jokes, we’d like to say we love what [Trent] has done. It’s definitely the last word in sound reactive lamps. Click through to see [Trent's] PCB, and the Butt Lamp in action.



  1. andres says:

    I laughed pretty hard, oh wow. I love it!

  2. BiOzZ says:


  3. andrew says:

    That will become the button of so many jokes.

  4. Eirinn says:

    I think this project is ass.


  5. voxnulla says:

    Fasster than light technology.
    Good thing this thing doesn’t require an old screw-in lightbulb.
    Never combine this with a lavalamp.
    Soon to be available on
    There is light on the dark side of the moon.
    Does this project meet energy star requirements?
    So this what photographers call backlight.
    This build, is it using LED’s? Light Emitting Derrière.

    Well, got it out of the system….

  6. ka1axy says:

    Fra-GEE-lay…must be Italian

  7. aztraph says:

    i like it but i like my stuff to be highly useful too

    • mh says:

      I wish you had at least told what one could expect to find when following the link (especially since it is far from obvious from the link itself) and how it relates to/differs from this.

      (I admit I was rash to mentally consider this spam, but gave it a chance. So in case anyone else have grown bitter like me and were avoiding the link out of habbit; it does seem relvevant)

    • aztraph says:

      how do you thing I feal, I just gave out my real name to the whole internet, and my Facebook account is public because I really do like to share stuff like this. I must be a gluten for punishment.

      And sorry about not sharing what the picture was, I wanted it to be a surprise, and I have to go low tech because I’m still learning how to use the arduino.

  8. Mcof says:

    This is literally asinine.

  9. No Hack says:

    Buttastic project!

  10. Slipster says:

    I believe I asked for a bud light not a butt light.

  11. Joseph says:

    A worthy successor to the “A Christmas Story” leg lamp.

  12. JimBob says:

    Could I have the top half? I want twin headlights!

  13. Jordan Earls says:

    Best part of this post is the tags

  14. Hirudinea says:

    Should have been solar, then you can tell people the sun does shine out of your ass.

  15. Chris C. says:

    [Trent] is really that kid from “A Christmas Story”, inspired by his dad’s leg lamp.

  16. NewCommentor1283 says:

    use lasers…
    then we really WILL be blinded by your a88
    lol XD

    PS: looks great

    • NewCommentor1283 says:

      if human eyes had tighter tolerances in manufacturing defect AND wear&tear
      (birth, use, ect)
      then we could make devices to cause temporary blindness
      without permenant damage,
      unfortuately that would require object recognition,
      accurate distance measurement,
      accurate measurement of current laser emmision power,
      AND a full detailed-upclose pre-examination of
      ALL eyes, and for all data to be numerically factored
      into determining laser power, focal point, and heating effects on retina.

      it needs to be recalculated at a rate GREATER then
      the rate of damage to the retina,
      at the laser power being emmitted. IN REAL TIME.

  17. dukeofmuffins says:

    Honestly I think the title is my favorite part of the post. :D

  18. pucebaboon says:

    Adam, Trent,

    Any h/w or s/w files available? The method of processing the MSGEQ7 output sounds
    interesting and the board looks fairly simple.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


Get every new post delivered to your Inbox.

Join 97,758 other followers