Assistive Radio Tells You What You Can’t See

November 22, 2025 by 2 Comments

We think of radios as audio devices, but for people who are visually impaired, it can be difficult to tell which channel you are listening to at any given time. [Sncarter] has a family member with vision impairment and built a radio to help her. Unfortunately, it was difficult to replicate, so he decided to try again. The result is an FM radio that provides audible status notifications about power and frequency. Check it out in the video below.

This isn’t just some hacked-up commercial radio, but a ground-up design that uses a TEA5767 with an ATMega328 for control. There is an LCD for when someone else might use the radio and an audio amplifier. He built the prototype on a breadboard, but moved the finished product to a PCB.

It isn’t just the electronics and the sound that are assistive. The case has raised bosses to help the user find things like the switch and rotary encoder. The Arduino can speak frequency announcements, although the quality of the voice is something he wants to tackle in the next revision.

These radios on a chip give you many design options. These same ideas can be useful for audiobook players, too.

A circular metal vessel is shown, with a symmetrical rotor of four vanes standing inside. At the bottom of the vessel are four loudspeakers.

Building An Acoustic Radiometer

November 22, 2025 by 12 Comments

A Crookes radiometer, despite what many explanations claim, does not work because of radiation pressure. When light strikes the vanes inside the near-vacuum chamber, it heats the vanes, which then impart some extra energy to gas molecules bouncing off of them, causing the vanes to be pushed in the opposite direction. On the other hand, however, it is possible to build a radiometer that spins because of radiation pressure differences, but it’s easier to use acoustic radiation than light.

[Ben Krasnow] built two sets of vanes out of laser-cut aluminium with sound-absorbing foam attached to one side, and mounted the vanes around a jewel bearing taken from an analog voltmeter. He positioned the rotor above four speakers in an acoustically well-sealed chamber, then played 130-decibel white noise on the speakers. The aluminium side of the vanes, which reflected more sound, experienced more pressure than the foam side, causing them to spin. [Ben] tested both sets of vanes, which had the foam mounted on opposite sides, and they spun in opposite directions, which suggests that the pressure difference really was causing them to spin, and not some acoustic streaming effect.

The process of creating such loud sounds burned out a number of speakers, so to prevent this, [Ben] monitored the temperature of a speaker coil at varying amounts of power. He realized that the resistance of the coil increased as it heated up, so by measuring its resistance, he could calculate the coil’s temperature and keep it from getting too hot. [Ben] also tested the radiometer’s performance when the chamber contained other gasses, including hydrogen, helium, carbon dioxide, and sulfur hexafluoride, but none worked as well as air did. It’s a bit counterintuitive that none of these widely-varying gasses worked better than air did, but it makes sense when one considers that speakers are designed to efficiently transfer energy to air.

It’s far from an efficient way to convert electrical power into motion, but we’ve also seen several engines powered by acoustic resonance. If you’d like to hear more about the original Crookes radiometers, [Ben]’s also explained those before.

A microscope objective is sitting on a spool of solder in a metal tin, in front of a circuit board which has wires running away from it.

Watching Radioactive Decay With A Homemade Spinthariscope

November 17, 2025 by 2 Comments

Among the many science toys that have fallen out of fashion since we started getting nervous around things like mercury, chlorinated hydrocarbons, and radiation is the spinthariscope, which let people watch the flashes of light on a phosphor screen as a radioactive material decayed behind it. In fact, they hardly expose their viewers to any radiation, which makes [stoppi]’s homemade spinthariscope much safer than it might first seem.

[Stoppi] built the spinthariscope out of the eyepiece of a telescope, a silver-doped zinc sulfide phosphor screen, and the americium-241 capsule from a smoke detector. A bit of epoxy holds the phosphor screen in the lens’s focal plane, and the americium capsule is mounted on a light filter and screwed onto the eyepiece. Since americium is mainly an alpha emitter, almost all of the radiation is contained within the device.

After sitting in a dark room for a few minutes to let one’s eyes adjust, it’s possible to see small flashes of light as alpha particles hit the phosphor screen. The flashes were too faint for a smartphone camera to pick up, so [stoppi] mounted it in a light-tight metal box with a photomultiplier and viewed the signal on an oscilloscope, which revealed many small pulses.

Continue reading “Watching Radioactive Decay With A Homemade Spinthariscope” →

Radio Apocalypse: Survivable Low-Frequency Communication System

November 12, 2025 by 17 Comments

In the global game of nuclear brinksmanship, secrets are the coin of the realm. This was especially true during the Cold War, when each side fielded armies of spies to ferret out what the other guy was up to, what their capabilities were, and how they planned to put them into action should the time come. Vast amounts of blood and treasure were expended, and as distasteful as the whole thing may be, at least it kept armageddon at bay.

But secrets sometimes work at cross-purposes to one’s goals, especially when one of those goals is deterrence. The whole idea behind mutually assured destruction, or MAD, was the certain knowledge that swift retaliation would follow any attempt at a nuclear first strike. That meant each side had to have confidence in the deadliness of the other’s capabilities, not only in terms of their warheads and their delivery platforms, but also in the systems that controlled and directed their use. One tiny gap in the systems used to transmit launch orders could spell the difference between atomic annihilation and at least the semblance of peace.

During the height of the Cold War, the aptly named Survivable Low-Frequency Communication System was a key part of the United States’ nuclear deterrence. Along with GWEN, HFGCS, and ERCS, SLFCS was part of the alphabet soup of radio systems designed to make sure the bombs got dropped, one way or another.

Continue reading “Radio Apocalypse: Survivable Low-Frequency Communication System” →

Radio Astronomy In The Palm Of Your Hand

October 17, 2025 by 5 Comments

When you think of a radio telescope, you usually think of a giant dish antenna pointing skyward. But [vhuvanmakes] built Wavy-Scope, a handheld radio telescope that can find the Sun and the Moon, among other things.

The build is relatively straightforward, using a commercial LNB to detect signals in the 10-12 GHz range. The detector is a simple satellite finder, although you could also connect it to a software-defined radio, if you wanted something more sophisticated.

Continue reading “Radio Astronomy In The Palm Of Your Hand” →

Hackaday Podcast Episode 342: Poopless Prints, Radio In Your Fillings, And One Hyperspectral Pixel At A Time

October 17, 2025 by 1 Comment

It was Elliot and Dan on the podcast today, taking a look at the best the week had to offer in terms of your hacks. We started with surprising news about the rapidly approaching Supercon keynote; no spoilers, but Star Trek fans such as we who don’t have tickets will be greatly disappointed.

Elliot waxed on about taking the poop out of your prints (not pants), Dan got into a camera that adds a dimension to its images, and we both delighted in the inner workings of an air-powered squishy robot.

Questions? We’ve got plenty. Is it possible to take an X-ray without an X-ray tube? Or X-rays, for that matter? Did Lucille Ball crack a spy ring with her fillings? Is Algol set to take over the world? What’s inside a germanium transistor? How does a flipping fish say Happy Birthday? And how far down the Meshtastic rabbit hole did our own Tom Nardi fall? Tune in to find out the answers.

Download this free-range, cruelty-free MP3.

Where to Follow Hackaday Podcast

Places to follow Hackaday podcasts:

Continue reading “Hackaday Podcast Episode 342: Poopless Prints, Radio In Your Fillings, And One Hyperspectral Pixel At A Time” →

[Anthony] holding the EE8 kit

Making A 2-Transistor AM Radio With A Philips Electronic Engineer EE8 Kit From 1966

October 12, 2025 by 42 Comments

Back in 1966, a suitable toy for a geeky kid was a radio kit. You could find simple crystal radio sets or some more advanced ones. But some lucky kids got the Philips Electronic Engineer EE8 Kit on Christmas morning. [Anthony Francis-Jones] shows us how to build a 2-transistor AM radio from a Philips Electronic Engineer EE8 Kit.

According to [The Radar Room], the kit wasn’t just an AM radio. It had multiple circuits to make (one at a time, of course), ranging from a code oscillator to a “wetness detector.”

The kit came with a breadboard and some overlays for the various circuits, along with the required components. It relied on springs, friction, and gravity to hold most of the components to the breadboard. A little wire is used, but mostly the components are connected to each other with their leads and spring terminals.

Continue reading “Making A 2-Transistor AM Radio With A Philips Electronic Engineer EE8 Kit From 1966” →