Author: Lewin Day

3425 Articles

Get Statistical About Your Pet With This Cat Tracking Dashboard

December 13, 2025 by 3 Comments

Cats can be wonderful companions, but they can also be aloof and boring to hang out with. If you want to get a little more out of the relationship, consider obsessively tracking your cat’s basic statistics with this display from [Matthew Sylvester].

The build is based around the Seeedstudio ReTerminal E1001/E1002 devices—basically an e-paper display with a programmable ESP32-S3 built right in. It’s upon this display that you will see all kinds of feline statistics being logged and graphed. The data itself comes from smart litterboxes, with [Matthew] figuring out how to grab data on weight and litterbox usage via APIs. In particular, he’s got the system working with PetKit gear as well as the Whisker Litter Robot 4. His dashboard can separately track data for four cats and merely needs the right account details to start pulling in data from the relevant cat cloud service.

For [Matthew], the build wasn’t just a bit of fun—it also proved very useful. When one of his cats had a medical issue recently, he was quickly able to pick up that something was wrong and seek the help required. That’s a pretty great result for any homebrew project. It’s unrelated, too, but Gnocci is a great name for a cat, so hats off for that one.

We’ve featured some other fun cat-tracking projects over the years, too. If you’re whipping up your own neat hardware to commune with, entertain, or otherwise interact with your cat, don’t hesitate to let us know on the tipsline.

Hidden Camera Build Proves You Can’t Trust Walnuts

December 12, 2025 by 10 Comments

Typically, if you happened across a walnut lying about, you might consider eating it or throwing it to a friendly squirrel. However, as [Penguin DIY] demonstrates, it’s perfectly possible to turn the humble nut into a clandestine surveillance device. It turns out the walnut worriers were right all along.

The build starts by splitting and hollowing out the walnut. From there, small holes are machined into the mating faces of the walnut, into which [Penguin DIY] glues small neodymium magnets. These allow the walnut to be opened and snapped shut as desired, while remaining indistinguishable from a regular walnut at a distance.

The walnut shell is loaded with nine tiny lithium-polymer cells, for a total of 270 mAh of battery capacity at 3.7 volts. Charging the cells is achieved via a deadbugged TP4056 charge module to save space, with power supplied via a USB C port. Holes are machined in the walnut shell for the USB C port as well as the camera lens, though one imagines the former could have been hidden purely inside for a stealthier look. The camera itself appears to be an all-in-one module with a transmitter built in, with the antenna installed in the top half of the walnut shell and connected via pogo pins. The video signal can be picked up at a distance via a receiver hooked up to a smart phone. No word on longevity, but the included batteries would probably provide an hour or two of transmission over short ranges if you’re lucky.

If you have a walnut tree in your backyard, please do not email us about your conspiracy theories that they are watching you. We get those more than you might think, and they are always upsetting to read. If, however, you’re interested in surveillance devices, we’ve featured projects built for detecting them before with varying levels of success. Video after the break.

Continue reading “Hidden Camera Build Proves You Can’t Trust Walnuts” →

Weird Email Appliance Becomes AI Terminal

December 12, 2025 by 5 Comments

The Landel Mailbug was a weird little thing. It combined a keyboard and a simple text display, and was intended to be a low-distraction method for checking your email. [CiferTech] decided to repurpose it, though, turning it into an AI console instead.

The first job was to crack the device open and figure out how to interface with the keyboard. The design was conventional, so reading the rows and columns of the key matrix was a cinch. [CiferTech] used PCF8574 IO expanders to make it easy to read the matrix with an ESP32 microcontroller over I2C. The ESP32 is paired with a small audio output module to allow it to run a text-to-speech system, and a character display to replace the original from the Mailbug itself. It uses its WiFi connection to query the ChatGPT API. Thus, when the user enters a query, the ESP32 runs it by ChatGPT, and then displays the output on the screen while also speaking it aloud.

[CiferTech] notes the build was inspired by AI terminals in retro movies, though we’re not sure what specifically it might be referencing. In any case, it does look retro and it does let you speak to a computer being, of a sort, so the job has been done. Overall, though, the build shows that you can build something clean and functional just by reusing and interfacing a well-built commercial product.

Continue reading “Weird Email Appliance Becomes AI Terminal” →

DIY Synth Takes Inspiration From Fretted Instruments

December 11, 2025 by 7 Comments

There are a million and one MIDI controllers and synths on the market, but sometimes it’s just more satisfying to make your own. [Turi Scandurra] very much went his own way when he put together his Diapasonix instrument.

Right away, the build is somewhat reminiscent of a stringed instrument, what with its buttons laid out in four “strings” of six “frets” each. Only, they’re not so much buttons, as individual sections of a capacitive touch controller. A Raspberry Pi Pico 2 is responsible for reading the 24 pads, with the aid of two MPR121 capacitive touch ICs.

The Diapasonix can be played as an instrument in its own right, using the AMY synthesis engine. This provides a huge range of patches from the Juno 6 and DX7 synthesizers of old. Onboard effects like delay and reverb can be used to alter the sound. Alternatively, it can be used as a MIDI controller, feeding its data to a PC attached over USB. It can be played in multiple modes, with either direct note triggers or with a “strumming” method instead.

We’ve featured a great many MIDI controllers over the years, from the artistic to the compact. Video after the break. Continue reading “DIY Synth Takes Inspiration From Fretted Instruments” →

A Musically-Reactive LED Christmas Tree

December 10, 2025 by 6 Comments

Regular Christmas trees don’t emit light, nor do they react to music. If you want both things in a holiday decoration, consider this build from [dbmaking]. 

An ESP32-D1 mini runs the show here. It’s hooked up to a strip of WS2812B addressable LEDs. The LED strip is placed on a wooden frame resembling the shape of a traditional Christmas tree. Ping-pong balls are then stacked inside the wooden frame such that they act as a light diffuser for the LEDs behind. The microcontroller is also hooked up to an INMP441 omnidirectional MEMS microphone module. This allows the ESP32 to detect sound and flash the LEDs in time, creating a colorful display that reacts to music. This is achieved by using the WLED web installer to set the display up in a sound reactive mode.

It’s a fun build, and we’d love to tinker around with coding more advanced visualizer effects for a build like this. We’ve seen builds that go the other way, too, by toning down excessive blinkiness in Christmas decorations.

Continue reading “A Musically-Reactive LED Christmas Tree” →

LED Hourglass Is A Great Learning Project

December 9, 2025 by 5 Comments

An hourglass tells you what it is in the name — a glass that you use to measure an hour of time passing by. [EDISON SCIENCE CORNER] has built a digital project that mimics such a thing, with little beads of light emulating falling sand in the timekeepers of old.

The build is designed around the Arduino platform, and can be constructed with an Arduino Uno, Nano, or Pro Mini if so desired. The microcontroller board is hooked up with an ADXL335 three-axis accelerometer, which is used for tracking the orientation and movement of the digital hourglass. These movements are used to influence the movement of emulated grains of sand, displayed on a pair of 8×8 LED matrixes driven by a MAX7219 driver IC. Power is courtesy of a 3.7 V lithium-ion cell, with a charge/boost module included for good measure. Everything is wrapped up in a vaguely hourglass-shaped 3D printed enclosure.

The operation is simple. When the hourglass is turned, the simulated grains of sand move as if responding to gravity. The movement is a little janky — no surprise given the limited resolution of the 8×8 displays. You also probably wouldn’t use such a device as a timer when more elegant solutions exist. However, that’s not to say builds like this don’t have a purpose. They’re actually a great way to get to grips with a microcontroller platform, as well as to learn about interfacing external hardware and working with LED matrixes. You can pick up a great deal of basic skills building something like this.

Would you believe this isn’t the first digital hourglass we’ve featured on the site?

Continue reading “LED Hourglass Is A Great Learning Project” →

Build Yourself A Graphing Weather Display

December 8, 2025 by 5 Comments

These days, Internet connectivity is ubiquitous, so you can look up live weather data on just about any device around you. Regardless, [Jozerworx] wanted a simple, clean, independent weather display, and came up with this simple design. 

The build is based on the Lilygo T5 EPD devboard, which combines an ESP32-S3 microcontroller with a nice 4.7-inch e-paper display. This display has the benefit that it only uses power when it’s being updated, making it particularly suitable to run off a battery for extended periods of time. Meanwhile, the ESP32 and its inbuilt Wi-Fi connectivity allow it to query the internet for updated weather forecasts. Weather data is sourced via the OpenWeather API, which [Jozerworx] notes comes with the caveat of requiring an API key. It’s a little fussy, but if you want good weather data, there are few easier ways to get it. The display shows a forecast for the next five days, while also showing graphs of ambient temperature and humidity along with useful information like the sunset and sunrise schedule.

Files are on Github for those eager to learn more. [Jozerworx] also notes that getting started with the display is particularly easy with the inclusion of a setup mode. This allows the display to act as a Wi-Fi access point with a web page that you use enter your home Wi-Fi connection details.

We’ve featured a great many charming weather displays over the years, too. If you’re working to plot, chart, or even predict the weather—don’t hesitate to show us your cool projects over on the tipsline!

Continue reading “Build Yourself A Graphing Weather Display” →