Audio-Forward Case Mod Of Classic 90s Portable TV

April 24, 2026 by Bryan Cockfield 8 Comments

The humble cathode ray tube (CRT) was once the technology behind almost all of our televisions and computer displays. Its replacements, from LCD screens to OLED and others, are generally cheaper to make and better to look at. Old televisions were comparatively large as well, but their size can be an advantage for people like [ManicMods] aka [Jeff]. His latest build ditches the CRT from an old Bently portable TV and uses the huge space available in the case for a hi-fi audio system and some other parts that turn it into an impressive portable home theater system.

After removing most of the internals of the TV, the first part to go in is the stereo and subwoofer combo as it takes up the most amount of space. The subwoofer section points downward and the two stereo speakers are mounted to the sides. To free up the most space inside, the new display is mounted forward of the original bezel, with a new 3D printed one helping to hold it in place. Behind it goes a Raspberry Pi, loaded with the moOde audio player, a high quality DAC for audio output, and a 1 TB SSD with [Jeff]’s uncompressed audio library. Most of the ports are extended out to the case including the SD card slot so other operating systems can be loaded on the Pi, and there are a ton of options for hooking up external speakers and displays as well, making it an extremely modular and expandable portable media center.

Also added to the finished product are a few small game controllers, since the Pi is perfectly capable of playing retro games, as well as a small wireless keyboard and trackpad combo. Although the CRT’s demise will be felt harder by some than by others, the original look of the case is preserved somewhat by keeping the original tuning display and locations of the original control buttons and knobs. If preserving the CRTs are of upmost importance, though, this build used a pair of them in a VR headset.

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Wearable MIDI Controller Built With Raspberry Pi

April 21, 2026 by Zoe Skyforest 7 Comments

Most synths happily get by with keyboard or pad inputs and make lovely sounds in response. [Becky Clarke] and her fellow collaborators are building a synth that works rather differently. DigitSynth is a wearable controller that’s rather fun to interact with.

The heart of the build is a Raspberry Pi 5. It’s set up to talk to a TI ADS1115 ADC chip that lets it read a bunch of analog flex sensors embedded in a right-hand glove, while the Pi can also read a bunch of tactile buttons activated by the left hand. The flex sensors are used to control synth parameters like LFO rate and filter cutoffs, while the buttons control chord changes. The Raspberry Pi runs custom code to read these devices and generate the requisite MIDI commands to send to a Roland JD-Xi synth which is responsible for actually making the sound. Both sets of fingers are also dotted with LEDs for visual feedback, controlled via a TLC59711 PWM driver.

It’s a fun build that creates some ethereal sounds in an intuitive way, thanks to the nature of the interface. We’ve featured some similar builds before, using the flexure of the hand to create musical soundscapes. Video after the break.

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A 3D-printed, split-flap display-having calculator with a Raspberry Pi Pico inside.

By Our Calculations, You’ll Love The Flapulator

April 14, 2026 by Kristina Panos 5 Comments

Oh sure, you’ve got calculators. There’s that phone program of course, and the one that comes with your OS, and the TI-86 and possibly RPN numbers you’ve had since high school.

But what you don’t have is a Flapulator, at least not until you build one. Possibly the be-all, end-all of physical calculating devices, the Flapulator does its calculating live on a split-flap display. It’s kind of slow and the accuracy is questionable, but the tactility is oh, so good.

This baby boasts a 6-digit display, where the decimal point and negative sign each require one digit. Inside is a Raspberry Pi Pico, which can calculate for around 4 hours on a full charge. But the coolest part (aside from the split-flap display, naturally) has got to be the 24-key, hand-wired mechanical keyboard. There’s also a couple of LEDs that light up to keep track of the current mathematical operation.

The story behind this one is kind of interesting. [Applepie1928] found out that one of their favorite mathematician-comedian-pi-lovers who is known for signing calculators was coming to town. With four weeks to whip something up, this was, amazingly, the result. Check it out in action after the break.

Need something that’s a whole other kind of fancy? Here’s an open-source graphing calculator.

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Simulating The AVR8 For A Browser-based Arduino Emulator

April 6, 2026 by Fenix Guthrie 10 Comments

It’s always nice to simulate a project before soldering a board together. Tools like QUCS run locally and work quite well for analog circuits, but can fall short with programmable logic. Tools like Wokwi handle the programmable side quite well but may have license issues or require the cloud. The Velxio project by [David Montero Crespo] is quite an excellent example of an (online) circuit simulator with programmable logic and local execution!

It’s built largely around Wowki’s AVR8JS library for Arduino simulation. All CPU simulation occurs on the local computer, while sketch compilation happens on the backend using official Arduino tools. But this was certainly not the most impressive aspect of the project. Likewise, Velxio features RP2040 execution using the rp2040js library. It also features the execution of some ESP32 derivative boards built around the RISC-V architecture using the RiscVCore.ts library.

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The Smallest Dialup ISP Is A Raspberry Pi And A Prison Phone

April 4, 2026 by Tyler August 27 Comments

There were a plethora of tiny, local ISPs in the days of dial-up internet. Along with the big providers, many cities would have more than one. Some of those have survived broadband, but none of them were as small as [Jeff Geerling]’s Pi ISP — a tiny dialup ISP built so his Aunt’s old G3 MacBook can get online at 36kbps, as God and [Robert Kahn] intended.

Hardware-wise, the Raspberry Pi is at one end of the chain, and your retrocomputer at another. In between, you’ll have a USB modem plugged into the Pi, and a device called a “two-way line simulator” to create a dial tone for that plain-old-telephone goodness. [Jeff] notes that these were commonly used in prisons for the phones that visitors use to talk to inmates.

Of course, since these devices are designed strictly for voice transmissions, which POTS was built for, you’re not going to get over 36 kbps, and that’s even with high-quality gear. The cheaper options might drop you down to 28k… just like with an ISP back in the day. ‘You get what you pay for’ is very rarely false.

Now, you can use this technology to just connect two computers together — as we’ve featured previously — but [Jeff] has gone the extra mile to put together, via Ansible, an easy-to-install software package that will let the Raspberry Pi act just like your ISP’s servers once did, and connect you to that series of tubes once called the World Wide Web. Of course, the World Wide Web isn’t built for dial-up anymore, so you’re going to be waiting… a while. Hackaday’s front page isn’t especially heavy, weighing about 4MB at the time of this writing, but that’s 15 minutes of load time, and you still aren’t reading the articles.

You also won’t be able to access much on old machines that can’t do HTTPS, but [Jeff] thought of that and bundles [rdmark]’s MacProxyClassic to translate the modern web into HTML tags that Netscape can understand and serve them over HTTP. You’ll still be waiting for our modern bloat, but perhaps not quite so long.

If you want the “authentic” dial-up experience, you’ll need to see the lightweight webpages of Yesteryear, and MacProxyClassic contains a Wayback Machine extension for that purpose. We featured a similar project a while back that did that, but without all the joys of dial-up. Now get off the computer, we’re expecting a call!

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The Raspberry Pi 4 With 3 GB RAM Is No Joke

April 2, 2026 by Maya Posch 60 Comments

Raspberry Pi 5 price increases. (Credit: Jeff Geerling)

Although easily dismissed by some as another cruel April Fools joke, Raspberry Pi’s announcement of a new 3 GB model of the Raspberry Pi 4 along with (more) price increases for other models was no joke. Courtesy of the ongoing RAMpocalypse, supplies of LPDDR4 and LPDDR5 are massively affected, leading to this new RPi 4 model with two 1.5 GB LPDDR4 chips, as these are apparently cheaper to source.

Affected in this latest price increase across RP’s product range are RPi 4 and 5 models with 4 or more GB of RAM, with price bumps ranging from $25 on the low end to $150 for the Raspberry Pi 500+. If you wanted a Raspberry Pi 5 with 16 GB of RAM, you’re now paying $300 for the privilege.

Obviously, this news has got people like [Jeff Geerling] rather down in the dumps, essentially stating that using SBCs like the RPi is now beyond the means of many hobbyists. While you can still use SBCs that use e.g. LPDDR2 RAM, such as the older RPi Zero, 2 and 3 models, [Jeff] himself is now moving more towards wrangling with snakes on MCUs, as these boards are so far not significantly affected in terms of price.

With current projections in the RAM market being that this year will still see more price increases, it remains hard to tell exactly how ‘temporary’ this situation will be. That said, using readily available, powerful and cheap MCUs like the ESP32 variants for projects isn’t a bad idea if you really don’t need to be running more than perhaps FreeRTOS.

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Battery Tester Outperforms Cheaper Options

April 1, 2026 by Bryan Cockfield 4 Comments

Batteries are notoriously difficult pieces of technology to deal with reliably. They often need specific temperatures, charge rates, can’t tolerate physical shocks or damage, and can fail catastrophically if all of their finicky needs aren’t met. And, adding insult to injury, for many chemistries, the voltage does not correlate to state of charge in meaningful ways. Battery testers take many efforts to mitigate these challenges, but often miss the mark for those who need high fidelity in their measurements. For that reason, [LiamTronix] built their own.

The main problem with the cheaper battery testers, at least for [LiamTronix]’s use cases, is that he has plenty of batteries that are too large to practically test on the low-current devices, or which have internal battery management systems (BMS) which can’t connect to these testers. The first circuit he built to help solve these issues is based on a shunt resistor, which lets a smaller IC chip monitor a much larger current by looking at voltage drop across a resistor with a small resistance value. The Pi uses a Python script which monitors the current draw over the course of the test and outputs the result on a handy graph.

This circuit worked well enough for smaller batteries, but for his larger batteries like the 72V one he built for his electric tractor, these methods could draw far too much power to be safe. So from there he built a much more robust circuit which uses four MOSFETs as part of four constant current sources to sink and measure the current from the battery. A Pi Zero monitors the voltage and current from the battery, and also turns on some fans pointed at the MOSFETs’ heat sink to keep them from overheating. The system can be configured to work for different batteries and different current draw rates, making it much more capable than anything off the shelf.

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