2026-01-28 23:00:48
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.
However, there are many engineering challenges to building a maser. For one thing, cavities are bigger than required for lasers. Sources of noise and the mitigations are different, too.
The maser grew out of radar research in the early 1950s. Charles Townes and others at Columbia University used ammonia in a cavity to produce a 24 GHz maser, completing it in 1953. For his work, he would share the 1964 Nobel Prize for physics with two Soviet physicists, Nikolay Basov and Alexander Prokhorov, who had also built a maser.
By 1960, the laser appeared, and the maser was nearly forgotten. After all, a visible-light laser is something anyone can immediately appreciate, and it has many spectacular applications.
At the time, the naming of maser vs laser was somewhat controversial. Townes wanted to recast the “M” in maser to mean “molecular,” and pushed to call lasers “optical masers.” But competitors wanted unique names for each type of emission, so lasers for light, grasers for gamma rays, xasers for X-rays, and so on. In the end, only maser and laser stuck.
Masers have uses beyond fancy physics experiments. Trying to detect signals that are just above the noise floor? Try a cryogenic maser amplifier. That’s one way the NASA Deep Space Network pulls in signals. (PDF) You cool a ruby, or other material, to just a bit of 4 °K and use the output of the resulting maser to pull out signals without adding much noise. This works well for radio astronomy, too.
Need an accurate time base? Over the long term, a cesium clock is the way to go. But over a short period, a hydrogen maser clock will offer less noise and drift. This is also important to radio astronomy for building systems to use very long baseline interferometry. The NASA network also uses masers as a frequency standard.
While we didn’t have our own masers until 1953, nature forms them in space. Water, hydroxyl, and silicon monoxide molecules in space can form natural masers. Scientists can use these astrophysical masers to map regions of space and measure velocities using Doppler shifts.
Harold Weaver found these in 1965 and, as you might expect, they operate without cavities, but still emit microwaves and are an important source of data for scientists studying space.
While traditional masers are difficult to build, modern material science may be setting the stage for a maser comeback. For example, using nitrogen-vacancy centers in diamonds rather than rubies can lead to masers that don’t require cryogenic cooling. A room-temperature maser could open up applications in much the same way that laser diodes made things possible that would not have been practical with high-voltage tubes and special gases.
Masers can produce signals that may be useful in quantum computing, too. So while you might think of the maser as a historical oddity, it is still around and still has an important job to do.
In a world where lasers are so cheap that they are a dollar-store cat toy, we’d love to see a cheap “maser on a chip” that works at room temperature might even put the maser in reach of us hackers. We hope we get there.
2026-01-28 20:00:27
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.
2026-01-28 17:00:44
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.
2026-01-28 14:00:16
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.
2026-01-28 11:00:59
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.
2026-01-28 08:00:56
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.
