Laser Harp Sets The Tone

In many ways, living here in the future is quite exiting. We have access to the world’s information instantaneously and can get plenty of exciting tools and hardware delivered to our homes in ways that people in the past with only a Sears catalog could only dream of. Lasers are of course among the exciting hardware available, which can be purchased with extremely high power levels. Provided the proper safety precautions are taken, that can lead to some interesting builds like this laser harp which uses a 3W laser for its strings.

[Cybercraftics]’ musical instrument is using a single laser to generate seven harp strings, using a fast stepper motor to rotate a mirror to precise locations, generating the effect via persistence of vision. Although he originally planned to use one Arduino for this project, the precise timing needed to keep the strings in the right place was getting corrupted by adding MIDI and the other musical parts to the project, so he split those out to a second Arduino.

Although his first prototype worked, he did have to experiment with the sensors used to detect his hand position on the instrument quite a bit before getting good results. This is where the higher power laser came into play, as the lower-powered ones weren’t quite bright enough. He also uses a pair of white gloves which help illuminate a blocked laser. With most of the issues ironed out, [Cybercraftics] notes that there’s room for improvement but still has a working instrument that seems like a blast to play. If you’re still stuck in the past without easy access to lasers, though, it’s worth noting that there are plenty of other ways to build futuristic instruments as well.

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self-stabilizing robot on tabletop

Taming The Wobble: An Arduino Self-Balancing Bot

Getting a robot to stand on two wheels without tipping over involves a challenging dance with the laws of physics. Self-balancing robots are a great way to get into control systems, sensor fusion, and embedded programming. This build by [mircemk] shows how to make one with just a few common components, an Arduino, and a bit of patience fine-tuning the PID controller.

At the heart of the bot is the MPU6050 – a combo accelerometer/gyroscope sensor that keeps track of tilt and movement. An Arduino Uno takes this data, runs it through a PID loop, and commands an L298N motor driver to adjust the speed and direction of two DC motors. The power comes from two Li-ion batteries feeding everything with enough juice to keep it upright. The rest of the magic lies in the tuning.

PID (Proportional-Integral-Derivative) control is what makes the robot stay balanced. Kp (proportional gain) determines how aggressively the motors respond to tilting. Kd (derivative gain) dampens oscillations, and Ki (integral gain) helps correct slow drifts. Set them wrong, and your bot either wobbles like a confused penguin or falls flat on its face. A good trick is to start with only Kp, then slowly add Kd and Ki until it stabilizes. Then don’t forget to calibrate your MPU6050; each sensor has unique offsets that need to be compensated in the code.

Once dialed in, the result is a robot that looks like it defies gravity. Whether you’re hacking it for fun, turning it into a segway-like ride, or using it as a learning tool, a balancing bot is a great way to sharpen your control system skills. For more inspiration, check out this earlier attempt from 2022, or these self-balancing robots (one with a little work) from a year before that. You can read up on [mircemk]’s project details here.

Physical Computing Used To Be A Thing

In the early 2000s, the idea that you could write programs on microcontrollers that did things in the physical world, like run motors or light up LEDs, was kind of new. At the time, most people thought of coding as stuff that stayed on the screen, or in cyberspace. This idea of writing code for physical gadgets was uncommon enough that it had a buzzword of its own: “physical computing”.

You never hear much about “physical computing” these days, but that’s not because the concept went away. Rather, it’s probably because it’s almost become the norm. I realized this as Tom Nardi and I were talking on the podcast about a number of apparently different trends that all point in the same direction.

We started off talking about the early days of the Arduino revolution. Sure, folks have been building hobby projects with microcontrollers built in before Arduino, but the combination of a standardized board, a wide-ranging software library, and abundant examples to learn from brought embedded programming to a much wider audience. And particularly, it brought this to an audience of beginners who were not only blinking an LED for the first time, but maybe even taking their first steps into coding. For many, the Arduino hello world was their coding hello world as well. These folks are “physical computing” natives.

Now, it’s to the point that when Arya goes to visit FOSDEM, an open-source software convention, there is hardware everywhere. Why? Because many successful software projects support open hardware, and many others run on it. People port their favorite programming languages to microcontroller platforms, and as they become more powerful, the lines between the “big” computers and the “micro” ones starts to blur.

And I think this is awesome. For one, it’s somehow more rewarding, when you’re just starting to learn to code, to see the letters you type cause something in the physical world to happen, even if it’s just blinking an LED. At the same time, everything has a microcontroller in it these days, and hacking on these devices is also another flavor of physical computing – there’s code in everything that you might think of as hardware. And with open licenses, everything being under version control, and more openness in open hardware than we’ve ever seen before, the open-source hardware world reflects the open-source software ethos.

Are we getting past the point where the hardware / software distinction is even worth making? And was “physical computing” just the buzzword for the final stages of blurring out those lines?

Hackaday Europe 2025 Welcomes David Cuartielles, Announces Friday Night Bring-a-Hack

If you’re coming to Hackaday Europe 2025, you’ve got just over a week to get your bags packed and head on out to Berlin. Of course you have tickets already, right? And if you were still on the fence, let us tempt you with our keynote talk and some news about the Friday night meetup, sponsored by Crowd Supply.

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The DIY Homing Keys

r/keebgirlies Is Totally a Thing Now

When [coral-bells] posted her first build to r/mechanicalkeyboards, she likely felt some trepidation. After all this is reddit we’re talking about, so right away you’ve got two layers of male-domination hobby.

Most of a lovely plant-themed keyboard.
Image by [coral-bells] via reddit
What she likely didn’t expect was to be upvoted into the tens of thousands, or to receive such a response from other girlies who came out of the woodwork to share their builds.

And so r/keebgirlies was born, and already has a few thousand members. This is a brand-new subreddit for women and non-binary folks who are into mechanical keyboards. As it says in the sidebar, men are welcome but limited to the comments for now, so don’t go trying to post your builds. The girlies are currently seeking moderators, so give that some thought.

As for [coral-bells]’ lovely build, this is an Epomaker MS68 with MMD Vivian V2 switches, and those flowery keycaps are from Etsy. She is currently waiting for supplies to mod a Yunzii AL66, but wants to build a kit at some point.

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Trinteract, a small space mouse, operating in Blender.

Trinteract Mini Space Mouse Does It In 3D

We’re not sure how we managed to miss this one, but better late than never, right? This is Trinteract, a 3-DOF input device that’s both open-source and Arduino compatible. There’s even a neat 3D-printed clip to add it to the side of your laptop.

Imagine navigating 2D and 3D environments, or flying around in Minecraft with ease. [Görkem]’s custom PCB features a Hall effect sensor which picks up readings from the magnet embedded in the bottom of the joystick. You can use any magnetic object as input. In the video below the break, [Görkem] shows a 3D-printed sphere with a disc magnet trapped inside as an alternative. The super-neat part is that the thing moves around entirely on flexures. You know how much we love flexures around here.

[Görkem] has written up a fantastic guide for those who must have one of their own. As a bonus, the guide details the background and thought process behind the design, which we love to see.

Don’t like magnets? This space mouse uses an accelerometer and a spring.

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Puzzle Bobble on a screen with a physical gadget in front

Crafting A Cardboard Tribute To Puzzle Bobble

What do you get when you cross cardboard, deodorant rollers, and a love for retro gaming? A marvel of DIY engineering that brings the arcade classic Puzzle Bobble to life—once again! Do you remember the original Puzzle Bobble aiming mechanism we featured 12 years ago? Now, creator [TomTilly] has returned with a revamped version, blending ingenuity with a touch of nostalgia. [Tom] truly is a Puzzle Bobble enthusiast. And who could argue that? The game’s simplicty makes for innocent yet addictive gameplay.

[Tom]’s new setup recreates Puzzle Bobble’s signature aiming mechanic using surprising materials: deodorant roller balls filled with hot glue (to diffuse LED colours), bamboo skewers, and rubber bands. At its heart is an Arduino UNO, which syncs the RGB LED ‘bubbles’ and a servo-driven aiming arm to the game’s real-time data. A Lua script monitors MAME’s memory locations to match the bubble colours and aimer position.

But this isn’t just a static display. [Tom] hints at a version 2.0: a fully functional controller complete with a handle. Imagine steering this tactile masterpiece through Puzzle Bobble’s frantic levels!

Need more inspiration? Check out other quirky hacks like [Tom]’s deodorant roller controller we featured in 2023. Whether you’re into cardboard mechanics or retro gaming, there’s no end to what clever hands can create.

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