Tech In Plain Sight: Projection Clocks

February 23, 2026 by No comments

You wake up in the middle of the night. Is it time to get up? Well, you can look at the nightstand clock. Unless your partner is in the way. Whoops. Even then, without your glasses, the time is just a fuzzball of light. You could ask Alexa, but that’s sure to wake your partner, too. The answer is a projection clock. In its modern form, it shoots a digital time display on a wall or ceiling with digits so large that you don’t need your glasses. If you can see the ceiling, you can tell what time it is.

New Tech

A modern invention, of course. No, not really. According to [Roger Russel], a UK patent in 1909 used an analog clock face and lightbulbs to project the clock face and hands on the ceiling. Unfortunately, [Roger’s] website is no more, but the Wayback Machine is on the job. You can see a device of the same type at the British Museum.

A modern projection clock on the ceiling.

In 1938, [Leendert Prins] filed for a patent on a similar projection clock. Sometimes known as “ceiling clocks” or “night clocks,” these devices often have a regular clock visible as well as a way to project the time. In the old days, this was often an image of a translucent analog clock lit up by light bulbs. In the modern era, it is almost always either LEDs or an LCD with a halogen backlight. Of course, there are many variations. A clock might use numbers on a rotating drum with a lamp behind it, for example.

Development

It isn’t hard to imagine someone putting a pocket watch in a magic lantern as a prototype. In general, some bright light source has to pass through a condenser lens. The light then travels through the LCD or translucent clock face. Finally, a projector lens expands the image.

We couldn’t find much about the actual history of old projection clocks outside of [Roger’s] defunct website. But if you can project an image and build a clock, all you need is the idea to combine them.

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Nuclear Waste Remediation By Proton Beam

February 23, 2026 by 7 Comments

One of the issues with nuclear power plants is that they produce long-lived radioactive waste. Storing spent nuclear fuel is a real problem. However, researchers at the Department of Energy’s Thomas Jefferson National Accelerator Facility have made strides not only to produce more electricity from spent fuel but also to break it down into shorter-lived nuclear waste. [Aman Tripathi] shares the details about NEWTON, a program to fire high-energy protons at a target to produce a flood of neutrons that can interact with nuclear waste. You can read the original press release, too.

Short-lived, of course, is a relative term. Unprocessed spent fuel may be dangerous for about 100,000 years. After the proposed processing, the danger period is down to “only” 300 years. On the plus side, the process generates a lot of heat, which you can convert to electricity in the usual way.

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How Safe Are Old Airbags, Anyway?

February 23, 2026 by 5 Comments

Automotive airbags are key safety devices that aim to reduce injuries and mortality in the event of motor vehicle accidents. These rapidly-inflating cushions act to soften the blow of an impact, catching occupants of the vehicle and preventing them from hitting hard parts of the vehicle’s interior.

Airbags are rigorously tested to perform as faultlessly as possible under all conditions. However, no system is perfect, and every automotive component has an expected service life. The question is—how old is too old when it comes to airbags? The answer is not exactly straightforward.
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Calculus By Oscilloscope

February 23, 2026 by 3 Comments

Even entry-level oscilloscopes today have simple math functions such as adding or subtracting two channels. But as [Arthur Pini] notes, more advanced scopes can now even do integration and differentiation. He writes about using these tools to make measurements on capacitors and inductors. The post in EDN is worth a read, even if your scope doesn’t offer this sort of math yet.

It makes sense that capacitors and inductors would benefit from this feature. After all, the current through a capacitor, for example, is proportional to the rate of change in the voltage across it. That’s a derivative. Since the scope can measure voltages, it can also differentiate to find the current.

The same idea applies to inductors, where the current through an inductor is related to the integral of the voltage across it. It is a simple matter to measure the voltages and perform an integration to determine the current.

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A Candle-Powered Light

February 23, 2026 by 12 Comments

For a little over two thousand years, the primary light sources after the sun had set were oil lamps and candles. This was well before the age of fossil fuels, so these oil lamps were often fueled with a labor-intensive agricultural product like olive oil. Candles were similarly difficult to make, made from tallow, beeswax, or even butter. Labor and materials costs aside, though, there’s a surprising amount of energy in these fuels and [Maciej Nowak Projects] has a generator that help these ancient light sources generate some electricity on the side.

The generator is based around a piece of technology called a thermoelectric generator (TEG), which produces a voltage potential when placed in a temperature gradient. These aren’t new technologies, but their typically low efficiencies limit where they can be effectively used. In this case, however, [Maciej Nowak] has gone to great effort to boost this efficiency as high as possible by using a huge radiator on the cool side of the TEG and another one on the hot side, which in this case is heated by a small tea candle. The electricity produced is sent to a tiny DC converter which regulates the voltage to 3.3V, which then powers two custom-built pedestal lamps on either side of the TEG, each with a high-efficiency LED mounted to a custom-made circuit board.

Although this is certainly not the first time a TEG has been set up to run a small lighting system, we do appreciate this one for its polish, design, and high efficiency. It would make a fitting addition to anyone’s emergency power outage kit as it really increases the amount of available light produced from any given candle. When taken to the extreme, though, thermoelectric generators can be made to produce a surprising amount of energy, provided they are placed in the right environment.

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Running In Printf

February 22, 2026 by 7 Comments

You may or may not know, but printf is a Turing-complete language, once you exploit all the strange and wonderful format characters in it (especially %n). But who has time to write code as printf modifiers? Now, thanks to [sebsite], you can at least write in a slightly higher level assembly language and compile to printf. Practical? No. Cool? Undeniably.

As an example, the page shows fizzbuzz written in the assembler:

<pre><code>alias i, fizz, buzz

->fizz ([i] + 1) % 3 == 0
->buzz ([i] + 1) % 5 == 0
->i [i] + 1
->exit [i] == 100

[i] if !![i] & ![fizz] & ![buzz]
"Fizz" if [fizz]
"Buzz" if [buzz]
"\n" if [i]</code></pre>
<pre>

The alias keyword defines constants and, owing to default values, sets i to zero, fizz to one, and buzz to 2. The “arrow” statements store a result into a variable (so the first assignment sets the resulting value into fizz).

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Testing The Pressure Limits For Glass In Water Cooling Blocks

February 22, 2026 by 11 Comments

Many people who use water cooling in their computer systems like to go full-bore with ‘aquarium’ aesthetic, which includes adding a window to their cooling blocks so that they see the water flowing through the window from behind the case’s window. Traditionally PMMA acrylic is used for these windows, as it’s quite durable and easy to handle.

Using glass offers some advantages over acrylic, but has its own disadvantages, most of all that it’s hard to process, but also that it’s known for shattering quite easily if pushed beyond its limits.

This is why [der8auer] as a manufacturer of such water blocks has now spent a few years investigating the viability of using glass for this purpose. First and foremost is safety, with an early prototype glass water block suddenly shattering without clear cause.

Although normally the water cooling loop is only expected to experience pressures of about 600 mbar, the new glass windows that are now entering mass-production had to be tested to their breaking point. This involves pumping water into a few test blocks until they fail, using the test rig that you can see above.

First the big GPU water block was tested, with the acrylic version breaking at around 8-9 bar, while the glass plate shattered at around 5 bar. The failure mode was also interesting, with the glass plate shattering into fragments, while the two acrylic plates tested failed in a completely different location and manner.

A smaller water block with glass window failed at about 10 bar, demonstrating mostly that smaller glass windows are a lot sturdier. Effectively glass windows in water cooling loops are viable, and they also do not suffer from e.g. discoloration, but you do give up a big chunk of your safety margin if your water cooling loop suffers a major pressurization event. Which of course should never happen, but we’re definitely looking forward to the upcoming field trials of these new water blocks.

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