Make Your Own ESP32-Based Person Sensor, No Special Hardware Needed

January 28, 2026 by 24 Comments

Home automation with high usefulness and low annoyance tends to rely on reliable person sensing, and [francescopace]’s ESPectre shows one way to do that cheaply and easily by leveraging hardware that’s already present on a common dev board.

ESPectre is an ESP32-based open source motion detector that detects movement without any cameras or microphones. It works similarly to millimeter-wave (mmWave) radar motion detectors in the sense that when a person moves, wireless signals are altered slightly as a result. ESPectre can detect this disturbance by watching and analyzing the Wi-Fi channel state information (CSI) and doing some very smart math and filtering. It’s cheap, easy to deploy and use, and even integrates with Home Assistant.

Combining a sensor like this with something else like a passive infrared (PIR) motion sensor is one way to get really robust results. But keep in mind that PIR only senses what it can see, whereas ESPectre works on WiFi, which can penetrate walls.

Since ESPectre supports low-cost ESP32 variants and is so simple to get up and running, it might be worth your time to give it a trial run. There’s even a browser-based ghost-dodging game [francescopace] put online that uses an ESPectre board plugged in over USB, which seems like a fun way to get a feel for what it can do.

Electric Lawnmower Gets RC Controls

January 27, 2026 by 21 Comments

Decades ago, shows like Star Trek, The Jetsons, and Lost in Space promised us a future full of helpful computers and robot assistants. Unfortunately, we haven’t quite gotten our general-purpose helper to do all of our tasks with a simple voice command yet. But if some sweat equity is applied, we can get machines to do specific tasks for us under some situations. [Max Maker] built this remote-controlled lawnmower which at least minimizes the physical labor he needs to do to cut his grass.

The first step in the project was to remove the human interface parts of the push mower and start working on a frame for the various control mechanisms. This includes adding an actuator to raise and lower the mower deck on the fly. Driving the new rear wheels are two wheelchair motors, which allow it to use differential steering, with a set of casters up front for maximum maneuverability. An Arduino Mega sits in a custom enclosure to control everything and receive the RC signals, alongside the mower’s batteries and the motor controllers for the drive wheels.

After some issues with programming, [Max] has an effective remote controlled mower that he can use to mulch leaves or cut grass without getting out of his chair. It would also make an excellent platform if he decides to fully automate it in the future, which is a project that has been done fairly effectively in the past even at much larger scales.

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How HP Calculators Communicate Over Infrared

January 27, 2026 by 10 Comments

For most people, calculators are cheap and simple devices used for little more than addition and the odd multiplication job. However, when you get into scientific and graphical calculators, the feature sets get a lot more interesting. For example, [Ready? Z80] has this excellent explainer on how HP’s older calculators handle infrared communications.

The video focuses on the HP 27S Scientific Calculator, which [Ready? Z80] found in an op-shop for just $5. Introduced in 1988, the HP-27S had the ability to dump screen data over an infrared link to a thermal printer to produce paper records of mundane high-school calculations or important engineering math. In the video, [Ready? Z80] explains the communication method with the aid of Hewlett-Packard’s own journal publication from October 1987, which lays out of the details of “the REDEYE Protocol.” Edgy stuff. It’s pretty straightforward to understand, with the calculator sending out bursts of data in six to eight pulses at a time, modulated onto a 32.768KHz square wave as is the norm. [Ready? Z80] then goes a step further, whipping up custom hardware to receive the signal and display the resulting data on a serial terminal. This is achieved with a TEC-1G single-board computer, based on the Z80 CPU, because that’s how [Ready? Z80] does things.

We’ve seen other great stuff from this channel before, too. For example, if you’ve ever wanted to multitask on the Z80, it’s entirely possible with the right techniques. Video after the break.

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Smoothie Bikes Turned Into Game Controllers

January 27, 2026 by 9 Comments

Smoothie bikes are a great way to make a nutritious beverage while getting a workout at the same time. [Tony Goacher] was approached by a local college, though, which had a problem with this technology. Namely, that students were using them and leaving them filthy. They posed a simple question—could these bikes become something else?

[Tony’s] solution was simple—the bikes would be turned into game controllers. This was easily achieved by fitting a bi-color disc into the blender assembly. As the wheel on the bike turns, it spins up the blender, with the disc inside. An ESP32 microcontroller paired with a light sensor is then able to count pulses as the disc spins, getting a readout of the blender’s current RPM. Working backwards, this can then be calculated out into the bike’s simulated road speed and used to play a basic game on an attached Raspberry Pi. Notably, the rig is setup such that the Raspberry Pi and one bike connect to an access point hosted by the other bike.  This is helpful, because it means neither bike has too many dangling cables that could get caught up in a wheel or chain.

We’ve seen many amusing game peripherals over the years, from salad spinners to turntables. Video after the break.

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Servicing The ‘Not Serviceable’ Bearings On A Vacuum Power Head

January 27, 2026 by 12 Comments

Everyone knows that bearings are a consumable wear item, and that the power head of a vacuum likely contains bearings that will eventually need to be replaced. Yet when the manufacturer wants you to toss out the entire roller and pay $80 for the privilege, that feels rather steep and unnecessary. In the case of [Mark Furneaux], the roller in the power head of his Filter Queen brand vacuum felt particularly over the top to toss, since it’s all fancy wood with very durable brushes.

One of the bearings had stopped being a bearing, resulting in the plastic that held it in place beginning to melt. Fortunately the damage hadn’t progressed to the point where printing a replacement was necessary, so instead it was time to figure out how to remove the bearings without permanent damage. The trick that the manufacturer used was to peen the ends of the metal shafts that the bearings fit onto, requiring some Dremel action to convince them to come off.

After some careful modifications like this, the remnants of the old bearings came off and their replacements could go on. Due to the metal shaft modifications, it is now mostly the plastic caps on either end which grip the bearings, but it seems to work well enough. For $2 in bearings and some labor on [Mark]’s end, he managed to keep a perfectly good roller brush out of the landfill, and future bearing replacements should be much easier.

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Running DOOM On Earbuds

January 27, 2026 by 4 Comments

In 1993, DOOM was a great game to play if you had a 486 with a VGA monitor and nothing to do all weekend. In 2026, you can play it on a set of earbuds instead, if for some reason that’s something you’ve always dreamed of doing.

The project comes to us from [Arin Sarkisian], who figured out that the Pinebuds Pro had enough processing power to run one of the seminal FPS games from the 1990s. Inside these earbuds is a Cortex-M4F, which is set to run at 100 MHz. [Arin] figured out it could easily be cranked up to 300 MHz with low power mode switched off, which would come in handy for one main reason. See, the earbuds might be able to run the DOOM engine, but they don’t have a display.

Thus, [Arin] figured the easiest way to get the video data out would be via the Cortex-M4F’s serial UART running at 2.4 mbps. Running the game at a resolution of 320 x 200 at 3 frames per second would consume this entire bandwidth. However, all those extra clock cycles allow running an MJPEG compression algorithm that allow spitting out up to 18 frames per second. Much better!

All that was left to do was to figure out a control scheme. To that end, a web server is set up off-board that passes key presses to the buds and accepts and displays the MJPEG stream to the player. If you’re so inclined you can even play the game yourself on the project website, though you might just have to get in a queue. In the meantime, you can watch the Twitch stream of whoever else is playing at the time.

Files are on GitHub—both the earbud firmware and the web interface used to play the game. It was perhaps only a matter of time until we saw DOOM on earbuds; no surprise given that we’ve already seen it played on everything from receipt printers to cookware. No matter how cliche, we’re going to keep publishing interesting DOOM ports—so keep them coming to the tipsline.

Thanks to [alialiali] for the tip!

Pi Compute Module Powers Fully Open Smartphone

January 27, 2026 by 61 Comments

With the powerful off-the-shelf hardware available to us common hardware hobbyist folk, how hard can it be to make a smartphone from scratch? Hence [V Electronics]’s Spirit smartphone project, with the video from a few months ago introducing the project.

As noted on the hardware overview page, everything about the project uses off the shelf parts and modules, except for the Raspberry Pi Compute Module 5 (CM5) carrier board. The LCD is a 5.5″, 1280×720 capacitive one currently, but this can be replaced with a compatible one later on, same as the camera and the CM5 board, with the latter swappable with any other CM5 or drop-in compatible solution.

The star of the show and the thing that puts the ‘phone’ in ‘smartphone’ is the Quectel EG25-GL LTE (4G) and GPS module which is also used in the still-not-very-open PinePhone. Although the design of the carrier board and the 3D printable enclosure are still somewhat in flux, the recent meeting notes show constant progress, raising the possibility that with perhaps some community effort this truly open hardware smartphone will become a reality.

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