Audio Reactive LED Strips Are Hard

April 14, 2026 by Jenny List 16 Comments

Back in 2017, Hackaday featured an audio reactive LED strip project from [Scott Lawson], that has over the years become an extremely popular choice for the party animals among us. We’re fascinated to read his retrospective analysis of the project, in which he looks at how it works in detail and explains that why for all its success, he’s still not satisfied with it.

Sound-to-light systems have been a staple of electronics for many decades, and have progressed from simple volume-based flashers and sequencers to complex DSP-driven affairs like his project. It’s particularly interesting to be reminded that the problem faced by the designer of such a system involves interfacing with human perception rather than making a pretty light show, and in that context it becomes more important to understand how humans perceive sound and light rather than to simply dump a visualization to the LEDs. We receive an introduction to some of the techniques used in speech recognition, because our brains are optimized to recognize activity in the speech frequency range, and in how humans register light intensity.

For all this sophistication and the impressive results it improves though, he’s not ready to call it complete. Making it work well with all musical genres is a challenge, as is that elusive human foot-tapping factor. He talks about using a neural network trained using accelerometer data from people listening to music, which can only be described as an exciting prospect. We genuinely look forward to seeing future versions of this project. Meanwhile if you’re curious, you can head back to 2017 and see our original coverage.

RGB LED Display Simply Solves The Ping-Pong Ball Problem

January 30, 2025 by Donald Papp 19 Comments

A few years ago [Brian McCafferty] created a nice big RGB LED panel in a poster frame that aimed to be easy to move, program, and display. We’d like to draw particular attention to one of his construction methods. On the software end of things there are multiple ways to get images onto a DIY RGB panel, but his assembly technique is worth keeping in mind.

The diameter of ping pong balls is a mismatch for the spacing of LEDs on a strip. The solution? A bit of force.

The technique we want to highlight is not the fact that he used table tennis balls as the diffusers, but rather the particular manner in which he used them. As diffusers, ping-pong balls are economical and they’re effective. But you know what else they are? An inconvenient size!

An LED strip with 30 LEDs per meter puts individual LEDs about 33 mm apart. A regulation ping-pong ball is 40 mm in diameter, making them just a wee bit too big to fit nicely. We’ve seen projects avoid this problem with modular frames that optimize spacing and layout. But [Brian]’s solution was simply to use force.

Observing that ping-pong balls don’t put up much of a fight and the size mismatch was relatively small, he just shoved those (slightly squashy) 40 mm globes into 33 mm spacing. It actually looks… perfectly fine!

We suspect that this method doesn’t scale indefinitely. Probably large displays like this 1200 pixel wall are not the right place to force a square peg into a round hole, but it sure seemed to hit the spot for his poster-sized display. Watch it in action in the video below, or see additional details on the project’s GitHub repository.

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Pac-Man Ghost Helps With Air Quality Sensing

October 21, 2024 by Bryan Cockfield 13 Comments

In the past, building construction methods generally didn’t worry much about air quality. There were enough gaps around windows, doors, siding, and flooring that a house could naturally “breathe” and do a decent enough job of making sure the occupants didn’t suffocate. Modern buildings, on the other hand, are extremely concerned with efficiency and go to great lengths to ensure that no air leaks in or out. This can be a problem for occupants though and generally requires some sort of mechanical ventilation, but to be on the safe side and keep an eye on it a CO2 sensor like this unique Pac-Man-inspired monitor can be helpful.

Although there are some ways to approximate indoor air quality with inexpensive sensors, [Tobias] decided on a dedicated CO2 sensor for accuracy and effectiveness, despite its relatively large cost of around $30. An ESP32 handles the data from the sensor and then outputs the results to an array of LEDs hidden inside a ghost modeled after the ones from the classic arcade game Pac-Man. There are 17 WS2812B LEDs in total installed on a custom PCB, with everything held together in the custom 3D printed ghost-shaped case. The LEDs change from green to red as the air quality gets worse, although a few preserve the ghost’s white eyes even as the colors change.

For anyone looking to recreate this project and keep an eye on their own air quality, [Tobias] has made everything from the code, the PCB, and the 3D printer files open source, and has used accessible hardware in the build as well. Although the CO2 sensors can indeed be pricey, there are a few less expensive ways of keeping an eye on indoor air quality. Some of these methods attempt to approximate CO2 levels indirectly, but current consensus is that there’s no real substitute for taking this measurement directly if that’s the metric targeted for your own air quality.

The BAPPR Keeps Your Addressable LED System Cool

July 27, 2024 by Alexander Rowsell 17 Comments

We all love a nice strip or grid of addressable LEDs. It can add flair or an artistic touch to many projects, and it can make gaming computers look extra 1337. However, providing enough current to a long strip of addressable LEDs can sometimes be difficult. Often a separate voltage rail is needed to supply enough juice. At the same time, continually sending out data to animate them can often use 100% of the microcontroller’s CPU power, especially if the serial bus is being bit-banged. A crash or badly timed interrupt can leave the system in a weird state and sometimes with the LEDs not displaying the correct colours. Or you might just want to enter a power-saving mode from time to time on your main MCU? Well, the BAPPR is designed to address all of these problems.

[TheMariday] created the BAPPR and made it fully open-source. It’s a switch-mode power supply that can accept anywhere from 7 V to 17 V and converts it into a strong 5 V rail for typical addressable LEDs. It also has a “smart” mode where it monitors the data line going to the LEDs to see if there is activity. If for some reason the system stops sending data, the BAPPR can intervene and shut off the power to the LEDs, which can help prevent strange colour combinations from being displayed while the system recovers. Once data starts flowing again, power is restored and the light party can resume.

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Why Are We Only Just Now Hearing About LED Beaded Curtains

August 31, 2023 by Zoe Skyforest 20 Comments

Beaded curtains are a pretty banal piece of home decor, unlikely to excite most interior design enthusiasts. Throw on some addressable LEDs, though, and you’ve got something eye-catching at the very least, as [Becky] demonstrates.

Joining the LED strands at the bottom made running the wiring easy but made walking through the blinds hard.

The project started with an existing beaded curtain as a base. A series of addressable LED strands were then carefully sewn to the beads using knots tied in plain sewing thread. The strands were configured as a single strand as far as the data lines were concerned, to make animation easy. Power was supplied to both ends of the strand to ensure nice and even brightness across the strands.

The brains of the system is a PixelBlaze controller, which makes it easy to wirelessly control the behavior of the strings. It’s the perfect tool for quickly whipping up fancy animations and pretty effects without hand-assembling a bunch of code yourself.

There was only a few problems with the project. [Becky] found a pretty passable LED beaded curtain from China midway through the project, which reduced her enthusiasm to finish the build. There were also issues walking through the curtain due to the wiring scheme she chose, where the bottom of one strand was connected to its neighbor.

Regardless, it’s a fun blinky build that brings some color to an otherwise drab doorway. It’s hard to complain about that! Video after the break.

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3d printed tiny gym in a box with mirror and led strip lighting

Get Pumped For This Miniature Gym

January 9, 2023 by Abe Connelly 5 Comments

[Duncan McIntyre] lives in the UK but participated in a secret Santa gift exchange for his Dutch friends’ Sinterklaas celebration. In traditional maker fashion, [Duncan] went overboard and created a miniature gym gift box, complete with flashing lights, music and a motorized lid.

[Duncan] used [TanyaAkinora]’s 3D printed tiny gym to outfit the box with tiny equipment, with a tiny mirror added to round out the tiny room. An ATmega328P was used as the main microcontroller to drive the MP3 player module and A4988 stepper motor controller. The stepper motor was attached to a drawer slide via a GT2 timing belt and pulley to actuate the lid. Power is provided through an 18V, 2A power supply with an LM7805 providing power to the ATmega328P and supporting logical elements. As an extra flourish, [Duncan] added some hardware audio signal peak detection, fed from the speaker output, which was then sampled by the ATmega328P to be able to flash the lights in time with the playing music. A micro switch detects when the front miniature door is opened to begin the sequence of lights, song and lid opening.

[Duncan] provides source on GitHub for those curious about the Arduino code and schematics. We’re fans of miniature pieces of ephemera and we’ve featured projects ranging from tiny 3D printed tiny escalators to tiny arcade cabinets.

Video after the break!

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