Author: Lewin Day

3366 Articles

A Simple Simulator For Model Rocket Performance

August 4, 2025 by 7 Comments

When building a model rocket, it can be fun to get into the maths of it all—calculating the expected performance of your build, and then seeing how it measures up in the real world. To aid in that task, [Rotislav Persion] has created a simple web-based simulator for charting the potential performance of your own rockets.

The calculator lets you key in the fundamentals of your hobby rocket. Punch in the diameter of your rocket, its mass, the standard rocket engine you’re using, and the diameter and delay time of your parachute, and it will chart the altitude profile expected during flight.

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Repairing An Obscure Apple II Clone

August 3, 2025 by 8 Comments

The Apple II was made in great numbers, as was the Commodore 64. But the Mimic Spartan? It was a weird Apple II clone that you needed a Commodore 64 to use. [ARC Javmaster] has found one of these obscure machines and has set about bringing it back to life. Check out the video below.

The story of the machine has been told online by one of the developers on the project, one [Brent Marykuca]. Basically, the Mimic Spartan was an Apple II clone that was intended to take advantage of a C64 as a host machine. It came in a beige box with a bunch of edge connectors and cables sticking out, and you were intended to nest it on the back of your C64 so it could hook up to all the ports. Then, you could use your machine as a C64 or an Apple II, or sort of… both… and even exchange data between both machines in some limited ways. There are also a few details of this obscure machine that have been collated by [Mike Naberezny], who is seeking the original disk that shipped with the machine when new.

It’s early days yet for [ARC Javmaster]’s efforts to restore the Mimic Spartan. Thus far, it’s had a clean and basic test. It was able to display a short line of text on a display before ceasing activity. A full boot hasn’t been achieved just yet, but we can’t wait to see where the resurrection efforts go next.

Back in the day, there were all kinds of Frankenstein computer cards that effectively put one kind of computer inside another. These days, you can condense an entire retro machine down to run on a single microcontroller.

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Keyboard Hero: A Barebones Alternative To The Guitar Version

August 3, 2025 by 8 Comments

Guitar Hero was all the rage for a few years, before the entire world apparently got sick of it overnight. Some diehards still remember the charms of rhythm games, though. Among them you might count [Joseph Valenti] and [Daniel Rodriguez], who built a Keyboard Hero game for their ECE 4760 class at Cornell.

Keyboard Hero differs quite fundamentally from Guitar Hero in one major way. Rather than having the player tackle a preset series of “notes,” the buttons to press are instead procedurally generated by the game based on incoming audio input. It only works with simple single-instrument piano music, but it does indeed work. A Raspberry Pi Pico is charged with analyzing incoming audio and assigning the proper notes. Another Pi Pico generates the VGA video output with the game graphics, which is kept in sync with the audio pumped out from the first Pico so the user can play the notes in time with the music. Rather than a guitar controller, Keyboard Hero instead relies on five plastic buttons assembled on a piece of wood. It works.

It’s obviously not as refined as the game that inspired it, but the procedural generation of “notes” reminds us of old-school rhythm game Audiosurf. Video after the break.

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Squishy Beyblades Made With 3D Printer Fail To Compete In The Arena

August 2, 2025 by 7 Comments

When Beyblades first came out a couple of decades ago, they quickly became a fad across Japan and several Western countries. There was a whole ecosystem of parts that you could buy and use to build competitive fighting spinning tops. These days, though — 3D printers are ubiquitous. There’s very little stopping you from printing whatever Beyblade-compatible parts your heart desires, as [JettKuso] demonstrates.

For [JettKuso], the rubber attack tips were a personal favorite. They had high grip on the plastic arena floor and would allow a top to make rapid, aggressive moves that would knock other tops out of the arena. Not desiring to import specific Beyblade parts at great expense, he decided to print some rubber tips and associated parts instead. The result? Squishy Beyblades!

[JettKuso] built various tops with official and custom TPU parts, and put them in battles to see what worked and what didn’t. In many cases, the TPU replacement parts didn’t make a big difference or proved worse than the standard parts. However, when [JettKuso] got crazy, he found one thing that kind of worked. A mega-heavy TPU top blade, which weighed as much as the standard metal rings, was able to successfully win battles against less competitive standard builds.

Ultimately, the video serves as a testament to the developers of the original toys themselves. It’s not so simple to just print up some parts and have them be competitive with the tried-and-tested gear that comes off the store shelves. The experience ultimately gave [JettKuso] a greater appreciation for all the thought that went into the commercial toys. Video after the break.

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Custom Bedroom Lighting Controlled By Alexa

August 2, 2025 by 3 Comments

[Arkandas] had a problem. They liked reading in bed, but their bedroom lamps weren’t cutting it—either too bright and direct, or too dim and diffuse. The solution was custom lighting, and a new project began.

The concept was simple—build a custom controller for a set of addressable LED lighting strips that would be installed in the bedroom. Specifically, in the headboard of the bed, providing controllable light directly where it was needed. The strips themselves were installed in aluminum channel with plastic diffusers to give a nice smooth light. [Arkandas] then tasked an ESP32 to control the strips, using the FastLED library to work with WS2812B LEDs, and also the Adafruit NeoPixel library for using SK6812 LEDs and their extra white channel. The ESP32 was set up to provide a web interface for direct control over the local network. [Arkandas] also made good use of the FauxmoESP library to enable the device to be controlled via Amazon Alexa, which fit nicely into their existing smarthome setup. Files are on Github for the curious.

The final build works well, creating a soft light in the habitable area of the bed that can also be readily controlled via voice commands or via web. We’ve seen the ESP32 do other great feats in this arena before, too, albeit of the more colorful variety. Meanwhile, if you’re cooking up your own smart lighting solutions, don’t hesitate to tell the tipsline!

You Can Make Your Own Floppy Drive Cleaning Disks

August 1, 2025 by 11 Comments

Once upon a time, you could buy floppy drive cleaning disks at just about any stationary or computer store. These days, they’re harder to find. If you want to build one yourself, though, you might do well to follow [Gammitin]’s fine example.

[Gammitin] has been down this road before, having built head cleaning disks before. This time, a US patent was the inspiration. It basically indicated that the spinning cleaning disc inside should be made of spunbonded polyester or spunbonded olefin (such as Dupont Tyvek)—so those materials were sought out.

The project began with [Gammitin] disassembling a standard floppy disk down to its bare components. The spindle was then separated from the magnetic platter, and refitted with a disc of Tyvek material using super glue. The disk housing was then glued back together with more super glue, and labelled as a “Floppy Cleaning Disk.” Using the disk is as simple as putting a few drops of isopropyl alcohol on the Tyvek material, and inserting it into a drive. [Gammitin] tested it with an old Olivetti machine, and found it cleaned up the heads nicely.

Sometimes, when a commercial product ceases to exist, you can just make your own at home. This is a great example of that ethos. If you’re cooking up your own tools and accessories to keep your old machines running, we’d love to hear all about it on the tipsline!

2025 One-Hertz Challenge: The Flip Disc Clock

August 1, 2025 by 1 Comment

Do you like buses, or do you just like the flippy-flappy displays they use to show route information? Either way, you’ll probably love the flip-disc clock created by [David Plass].

The build is based around four seven-segment flip disc displays. The modules in question are from Flipo.io. They use a hefty 0.5 amp pulse to create a magnetic field strong enough to flip the discs from one side to the other with coils placed underneath the fluro/black flipdots themselves. The modules are controlled by a Wemos D1, which uses Wi-Fi to query a NTP server to keep accurate time. It then drives the necessary segments to display the current time. The whole thing is assembled in what appears to be some kind of kitchen storage tub.

Notably, the clock flips a couple dots once every second to meet the requirements of our One-Hertz Challenge. This also makes it obvious that the clock is working when it would otherwise be static. However, [David] notes commenting out that part of the code at times, as it can be quite loud!

This clock has got fluro dots, it’s well-executed, and it’s a fine entry to the 2025 One-Hertz Challenge. We’ve also previously explored how these beautiful displays work in detail, too. Meanwhile, if you’re busy repurposing some other kind of mechanical display technology, don’t hesitate to let us know!

 

 

 

2025 Hackaday One Hertz Challenge