A rough cut piece of wood sits on a workbench. A light and a tumbleweed are mounted on top so that the light shines through the tumbleweed. A woman in a ball cap and white tank top is crouched in the background smiling.

Cisco Ball Is The Tumbleweed Opposite Of A Disco Ball

August 5, 2024 by Navarre Bartz 8 Comments

Inspiration can strike a maker at any moment. For [Laura Kampf], it happened in the desert when she saw a tumbleweed.

Tumbleweeds roll through the western United States, hitting cars on the interstate and providing some background motion for westerns. [Kampf] found the plant’s intricate, prickly structure mesmerizing, and decided to turn it into a piece of contemplative kinetic art.

[Kampf] attached the tumbleweed to a piece of wood using epoxy and mounted it to what appears to be a worm drive motor nestled inside an interestingly-shaped piece of wood. As the tumbleweed turns, a light shines through it to project a changing shadow on the wall to “create silence, it creates calmness, it takes away from the noise that surrounds it.” While [Kampf] has some work to do to get the sculpture to its finished state, we can get behind her mantra, “The most important thing about the phase of execution is to get started.”

Are you looking for some projects of your own to help you find calm? How about some ambient lighting, a sand drawing table, or a music player that keeps things simple?

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Spin Your Own Passive Cooling Fibres

July 31, 2024 by Jenny List 4 Comments

When the temperature climbs, it’s an eternal problem: how to stay cool. An exciting field of materials science lies in radiative cooling materials, things which reflect so much incoming heat that they can cool down from their own radiation rather than heating up in the sun. It’s something [NightHawkInLight] has been working on over a series, and he’s dropped a very long video we’ve placed below. It’s ostensibly about spinning radiative cooling fibers, but in fact provides a huge quantity of background as well as a bonus explanation of cotton candy machines.

These materials achieve their reflectivity by creating a surface full of microscopic bubbles. It’s the same process that makes snow so white and reflective, and in this case it’s achieved by dissolving a polymer in a mixture of two solvents. The lower boiling point solvent evaporates first leaving the polymer full of microscopic bubbles of the higher boiling point solvent, and once these evaporate they leave behind the tiny voids. In the video he’s using PLA, and we see him experimenting with different solvents and lubricants to achieve the desired result. The cotton candy machine comes in trying to create fibers by melting solid samples, something which doesn’t work as well as it could so instead he draws them by hand with a small rake.

When he tests his mat of fibers in bright sunlight the effect is almost magical if we didn’t already know the mechanism, they cool down by a few degrees compared to ambient temperature and the surrounding control materials. This is a fascinating material, and we hope we’ll see more experimenters working with it. You won’t be surprised to hear we’ve featured his work before.

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Plight Of The Lowly Numitron Tube

July 8, 2024 by Adam Fabio 17 Comments

In the 60’s and 70’s there were many ways to display numeric data. Nixie tubes, Vacuum Florescent Displays (VFD), micro projection systems, you name it. All of them had advantages and drawbacks. One of the simplest ways to display data was the RCA Numitron. [Alec] at Technology Connections has a bit of a love/hate relationship with these displays.

The Numitron is simply a seven-segment display built from light bulb filaments. The filaments run at 5 V, and by their nature are current limited. Seven elements versus the usual ten seen in Nixie tubes reduced the number of switching elements (transistors, relays, or tubes) needed to drive them, and the single low-voltage supply was also much simpler than Nixie or even VFD systems.

Sounds perfect, right? Well, [Alec] has a bone to pick with this technology. The displays were quite dim, poorly assembled, and not very pleasing to look at. RCA didn’t bother tilting the “8” to fit the decimal point in! Even the display background was gray, causing the numbers to wash out in ambient light. Black would have been much better. In [Alec]’s words, the best way to describe the display would be “Janky,” yet he still enjoys them. In fact, he built a fancy retro-industrial-themed clock with them.

The Numitron was not a failure, though — we know variants of this display ended up in everything from gas pumps to aircraft cockpit gauges. You can even build an LED-based replica clock — no glowing filaments necessary.

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PeLEDs: Using Perovskites To Create LEDs Which Also Sense Light

July 7, 2024 by Maya Posch 12 Comments

With both of the dominant display technologies today – LCD and OLED – being far from perfect, there is still plenty of room in the market for the Next Big Thing. One of the technologies being worked on is called PeLED, for Perovskite LED. As a semiconductor material, it can both be induced to emit photons as well as respond rather strongly to incoming photons. That is a trick that today’s displays haven’t managed without integrating additional sensors. This technology could be used to create e.g. touch screens without additional hardware, as recently demonstrated by [Chunxiong Bao] and colleagues at Linköping University in Sweden and Nanjing University in China.

Their paper in Nature Electronics describes the construction of photo-responsive metal halide perovskite pixels, covering the typical red (CsPbI_3−xBr_x), green (FAPbBr₃), and blue (CsPbBr_3−xCl_x) wavelengths. The article also describes the display’s photo-sensing ability to determine where a finger is placed on the display. In addition, it can work as an ambient light sensor, a scanner, and a solar cell to charge a capacitor. In related research by [Yun Gao] et al. in Nature Electronics, PeLEDs are demonstrated with 1 microsecond response time.

As usual with perovskites, their lack of stability remains their primary obstacle. In the article by [Chunxiong Bao] et al. the manufactured device with red pixels was reduced to 80% of initial brightness after 18.5 hours. While protecting the perovskites from oxygen, moisture, etc. helps, this inherent instability may prevent PeLEDs from ever becoming commercialized in display technology. Sounds like a great challenge for the next Hackaday Prize!

A solar-powered decibel meter the size of a business card.

2024 Business Card Challenge: NoiseCard Judges The Sound Around You

June 22, 2024 by Kristina Panos 6 Comments

Let’s face it: even with the rise of the electric car, the world is a noisy place. And it seems like it has only gotten worse in recent years. But how can we easily quantify the noise around us and know whether it is considered an unhealthy decibel level?

That is where the NoiseCard comes in. This solar-powered solution can go anywhere from the regrettable open office plan to the busy street, thanks to a couple of 330 µF capacitors. It’s based on the low-power STM32G031J6 and uses a MEMS microphone to pick up sound from the back of the card, which the code is optimized for. Meanwhile, the LEDs on the front indicate the ambient noise level, ranging from a quiet 40 dB and under to an ear-splitting 105 dB or greater.

When it comes to building something the size of a business card, every component is under scrutiny for size and usefulness. So even the LEDs are optimized for brightness and low power consumption. Be sure to check it out in action after the break in various environments.

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A Peek Inside Apple Durability Testing Labs

June 10, 2024 by Dave Rowntree 19 Comments

Apple is well-known for its secrecy, which is understandable given the high stakes in the high-end mobile phone industry. It’s interesting to get a glimpse inside its durability labs and see the equipment and processes it uses to support its IP68 ingress claims, determine drop ability, and perform accelerated wear and tear testing.

Check out these cool custom-built machines on display! They verify designs against a sliding scale of water ingress tests. At the bottom end is IPx4 for a light shower, but basically no pressure. Next up is IPx5, which covers low-pressure ambient-temperature spray jets from all angles – we really liked this machine! Finally, the top-end IPx7 and IPx8 are tested with a literal fire hose blast and a dip in a static pressure tank, simulating a significant depth of water. An Epson robot arm with a custom gripper is programmed to perform a spinning drop onto a hard surface in a repeatable manner. The drop surface is swapped out for each run – anything from a wooden sheet to a slab of asphalt can be tried. High-speed cameras record the motion in enough detail to resolve the vibrations of the titanium shell upon impact!

Accelerated wear and tear testing is carried out using a shake table, which can be adjusted to match the specific frequencies of a car engine or a subway train. Additionally, there’s an interview with the head of Apple’s hardware division discussing the tradeoffs between repairability and durability. He makes some good points that suggest if modern phones are more reliable and have fewer failures, then durability can be prioritized in the design, as long as the battery can still be replaced.

The repairability debate has been raging strong for many years now. Here’s our guide to the responsible use of new technology.

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Gas-Tight FDM 3D Printing Is Within Your Grasp

June 8, 2024 by Jenny List 65 Comments

The widespread availability of inexpensive 3D printers has brought about a revolution in what can be easily made at home. However these creations aren’t perfect, particularly when it comes to the adhesion between their layers. Aside from structural failures along the layer lines there is also the question of those joins being permeable, limiting the possibility for waterproof or gas proof prints. It’s something [German Engineer] has tackled in a new video, in which he’s looking at the design and preparation of small propane tanks.

A blurry image of a red 3d-printed part exploding — This is the frame at which the 3D printed tank explodes

The attraction of propane as a fuel is that it liquefies easily on compression, so a propane cylinder or tank will be an equilibrium of liquid propane with pressurized gas above it, whose pressure depends on the ambient temperature. This means that any tank must be expected to have a working pressure somewhere between 150 and 200 PSI, with of course a design pressure far exceeding that for safety reasons.

Filling a 3D printed tank immediately results in the propane escaping, as he demonstrates by putting one of his prints under water. He solves this with a sealant, Diamant Dichtol, which is intended to polymerize in the gaps between layers and create a gas-tight tank. A range of three tanks of different thicknesses are treated this way, and while the 1 mm thick variety bursts, the thicker ones survive.

It’s clear that this technique successfully creates gas-tight prints, and we can see the attraction of a small and lightweight fuel tank. But we can’t help worrying slightly about the safety, for even when the material is a lightweight 3D print, high pressure equipment is not to be trifled with. Tanks do burst, and when that happens anyone unfortunate enough to be close by sustains nasty, even life-threatening injuries. Use the technique, but maybe don’t hit it with high pressures.

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