Hacking A Cat Litter Box

August 21, 2026 by Zoe Skyforest No comments

[Joseph DiGiovanni] is the owner of a Litter Robot 4. It’s a convenient mechanized litter box for cats that can clean itself to reduce unwelcome odors inside the home. He wanted to run automations based on the operation of the litter box, but was not eager to use the manufacturer’s cloud service to do it. Instead, he set about reverse engineering the device for his own ends.

Since the Litter Robot 4 relies on an ESP32 microcontroller for external connectivity, it was entirely possible for [Joseph] to whip up a custom firmware for the device instead. He started with ESPHome as a base, which is a popular firmware used for building smarthome devices based on Espressif hardware. The architecture of the Litter Robot 4 helped in this regard. It uses a PIC microcontroller to handle the low level hardware control, while the ESP32 is responsible for connecting to the cloud over WiFi. This allowed [Joseph] to mess with the connectivity features and get the device hooked up to Home Assistant without compromising the basic mechancial functionality of the device or any of the safety features.

All [Joseph] had to do was figure out how the original hardware’s ESP32 talked to the PIC and emulate that in his own firmware, which was achieved with some snooping and data capture and processing with an LLM. This was used as a basis to whip up an ESPHome firmware that could integrate the hardware neatly with Home Assistant.

Files are on Codeberg for those eager to tinker. It’s not the first time we’ve looked at cat litter management, and it won’t be the last. Video after the break.

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How The Grid’s Harmonic Filters Keep The Power Clean

August 21, 2026 by Maya Posch 1 Comment

A fun way to think about a national electrical grid is as a massively upscaled electrical circuit, one in which you have multiple power supplies injecting AC power, with various bits and bobs involving resistors, inductors and capacitors in between working to synchronize and clean-up this power before it gets to the end users. Recently [Jordan Taylor], also known as [The Electric Brit] took a look at the grid’s harmonic filters that do a lot of this sinewave scrubbing after the HVDC to AC conversion.

Using a UK-based line-commutated converter (LCC) HVDC converter station as a physical example [Jordan] takes us through the elements of this harmonic filter, what it is, what it does and why it’s a necessity. The design considerations with components at this immense scale are also covered, along with the types of filters possible.

The Cliff’s Notes version is that following the conversion step from said HVDC there are harmonics introduced in the AC, not unlike in a much lower-voltage converter. This results in a noisy sinewave that can potentially cause harm to AC-powered devices, not to mention cause heating and other losses along the way. The answer is naturally to add an LC-filter, just on a slightly larger scale than for consumer electronics.

Also noted by [Jordan] is the nice synergy of these harmonic filters when it comes to absorbing and generating reactive power on the AC grid, due to their massive capacitors and inductors. This helps to dampen oscillations on the grid and thus further contributing to its stability.

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Building A Hammond Organ To Understand How They Work

August 21, 2026 by Tyler August 4 Comments

The Hammond organ is an early form of electronic– or perhaps electromechanical– musical instrument. It solved the very real problem of organs normally being the sort of thing you built into a cathedral, allowing a similar sound to fit into a piano-like form factor. Their workings are a so simple that it’s hard to wrap your head around it actually working– which is why [Uri Tuchman] built one on YouTube. Also for a gift exchange, but we’re not Santa, here– we’re here to learn, and [Uri] does not disappoint.

[Uri]’s organ is a bit smaller than what the Hammond corporation was putting out back in the day, just one hand-cranked octave– and it lacks the distinct spinning speaker in favour of plugging into any old guitar amp. It’s enough to get the idea across. Each of the twelve keys acts as a simple switch, wired to a pickup made from a coil of wire around a steel rod– much like a magnetic pickup on an electric guitar. The pickup faces the tone wheel, which is the part that feels like magic: the tonewheel spinning past the pickup acts exactly like the steel string vibrating in an electric guitar, its ferroelectric motions inducing a tiny current. The tonewheels smooth teeth are spaced to create sine waves at the frequencies corresponding to each key, so it has to be exact. That’s why while the rest of the brass-and-wood build is [Uri]’s beautiful craftsmanship, the iron tonewheels are CNC’d.

Aside from the amp it is plugged into, there are no electronics here. There’s nothing to double or otherwise alter the frequencies: one key means one tonewheel– twelve for this build– and if the RPMs are off everything is out of tune. Good thing [Uri] made it hand-cranked! Well, it is for a gift exchange. Maybe it’s a white elephant sort of thing, because we can only imagine that making it much harder to play. On the other hand, [Uri] demonstrates some neat effects by varying the RPM at the end of the video, so perhaps that’s a feature.

As nice as [Uri]’s work is, Hammond Organ Company filmed the construction themselves, back in the day if you want to see the true quill. Alternatively, you can get more of [Uri]’s craftsmanship with this square guitar.

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Thermoacoustic Sterling Engine Is Now Fully 3D Printable

August 21, 2026 by Tyler August 8 Comments

Would you like to make your own energy? Why, who doesn’t in this era of rising costs! A sterling engine always looks like a good fit for that: highly efficient, with no risk of a boiler explosion. A thermoacoustic sterling engine looks even better, since it has only one moving part at the output end. A thermoacoustic sterling engine you can 3D print yourself looks best of all, and that’s what [my engines] has on offer, now that even the burner and hot end of his thermoacoustic engine are designed for SLA metal printing.

We previously reported on the open-source engine, but there’ve been some improvements worth talking about. For one thing, he’s integrated a biogas/methane burner directly inside the 3D-printable hotend. For another, that 3D-printed design allows for an excellent heat exchange geometry that would be very hard to get any other way. The whole thing is open source with plans available at OwnEnergy.org, where you can find links to the apparently-mandatory Discord channel and now an old-style forum to actually collaborate on the design, which is open-source. The site is also now the home of all data and discussion about [my engines]’s homescale biogas plant, which is the power source for this little engine.

If you’d rather print a combustion engine, you can do that, too, but you’ll need more “vitamins” than this unit requires.

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PVC Pipe Turned DIY Digital Telescope

August 21, 2026 by Zoe Skyforest 5 Comments

[Makestreme] had always wanted to own a nice telescope, but found that budget would not stretch to anything above a cheap model with a limited 50 mm aperture. Wanting a better view of the heavens, the way forward was obvious—it was time to build a better telescope, instead!

The build is based around a 114 mm diameter mirror sourced from Amazon. It’s assembled inside a length of 5-inch PVC pipe of just under a meter to suit the 900 mm focal length of the concave reflector. 3D printed components are used to mount the mirror and control its position for proper focus and collimation. Traditionally, a reflector based telescope would use a mirror and eyepiece to provide a view to the user. However, [Makestreme] built this as a smart telescope, instead integrating a Raspberry Pi Camera Module 3 at the focal point. It’s connected to a Raspberry Pi Zero 2W, running off an 18650 lithium-ion cell and a 5 V boost module for portability. The Pi runs a Python script that hosts a small web server allowing access to the live camera feed along with controls for brightness, exposure, and gain. [Makestreme] then uses apps like SkyMap and SkEye to help aim the telescope at astronomical elements of interest.

If you’ve ever wanted to explore the heavens from down on Earth, building your own telescope is a great way to start. A camera-based build like this one can be a bit simpler than traditional builds, too, without the fuss of having to install an eyepiece.

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Hackaday Podcast Episode 383: QR Codes, Caving Gear, And The Old School Way To Learn Electronics

August 21, 2026 by Tom Nardi 1 Comment

In this week’s episode, Hackaday Editors Elliot Williams and Tom Nardi start things off by getting excited about the recently announced 2026 Retrocomputing Challenge. From there the conversation will cover efforts to improve desktop 3D printing with lasers, an expensive grill with an ESP32 controller and an open source firmware, open source tools underground, and some impressive techniques to squeeze a bit more utility out of the common QR code.

You’ll also hear about turning PVC pipes into flat stock, old school Radio Shack electronic kits, and VR soldering demos. Stick around to the end of the episode learn about the latest developments in over-the-counter hearing aids and the 1-bit CPU that’s enjoying an unexpected fandom nearly 50 years after its release.

Check out the links if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download in DRM-free MP3.

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Building A Discrete Component 75 Baud Modem

August 21, 2026 by Zoe Skyforest 9 Comments

These days, modems are pretty fancy bits of kit, what with to keep up with the speeds of cable, VDSL, and fiber connections. At lower speeds, though, it’s entirely possible to build a modem out of simple discrete components. [sv3ora] did just that, building a simple modem for the CB2 Micro.

The project takes advantage of the fact that the V1.54 firmware for the CB2 Micro enabled 75 baud serial communication. Thus, it made sense for [sv3ora] to build a 75 baud modem to suit. As was the way in the days of dial-up internet, the modem modulates data into audio, demodulates audio back into data, allowing the CB2 Micro to send and receive data over telephone lines, ham radio links, or to store and retrieve data via mediums like cassette tape.

The device is built out of good old BC547 transistors. along with a smattering of diodes, resistors, and capacitors as supporting hardware. That’s all you need to turn slow serial into audio and back again. [sv3ora] does a great job of demoing the hardware, using it to store a program on tape and retrieve it again later.

We love old school modems around these parts. We’ve even explored ways to build your own dial-up ISP in the past!

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