The Amazing Maser

January 28, 2026 by No comments

While it has become a word, laser used to be an acronym: “light amplification by stimulated emission of radiation”. But there is an even older technology called a maser, which is the same acronym but with light switched out for microwaves. If you’ve never heard of masers, you might be tempted to dismiss them as early proto-lasers that are obsolete. But you’d be wrong! Masers keep showing up in places you’d never expect: radio telescopes, atomic clocks, deep-space tracking, and even some bleeding-edge quantum experiments. And depending on how a few materials and microwave engineering problems shake out, masers might be headed for a second golden age.

Simplistically, the maser is — in one sense — a “lower frequency laser.” Just like a laser, stimulated emission is what makes it work. You prepare a bunch of atoms or molecules in an excited energy state (a population inversion), and then a passing photon of the right frequency triggers them to drop to a lower state while emitting a second photon that matches the first with the same frequency, phase, and direction. Do that in a resonant cavity and you’ve got gain, coherence, and a remarkably clean signal.

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

January 28, 2026 by 8 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.

Computer History Museum Opens Virtually

January 28, 2026 by 5 Comments

If your travels take you near Mountain View, California, you can have the pleasure of visiting the Computer History Museum. You can see everything from a PDP-1 to an Altair 8800 to a modern PC there. If you aren’t travelling, the museum has launched a digital portal that expands your ability to enjoy its collection remotely.

CEO Marc Etkind said, “OpenCHM is designed to inspire discovery, spark curiosity, and make the stories of the digital age more accessible to everyone, everywhere. We’re unlocking the collection for new audiences to explore.”

The portal features advanced search tools along with browsable curated collections and stories. There’s also an album feature so you can create and share your own custom collections. If you are a developer, the portal also allows access via an API.

As an example, we checked out the vintage marketing collection. Inside were a 1955 brochure for a Bendix computer you could lease for under $1,000 a month, and a 1969 brochure for the high-performance Hitachi HITEC 10. It had 4K words of 16-bit memory and a clock just a bit more than 700 kHz, among others.

If you are on the other side of the Atlantic, you might want to check out a very large museum there. There’s also a fine museum in the UK.

Electric Lawnmower Gets RC Controls

January 27, 2026 by 6 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 2 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 5 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 10 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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