Solar Light? Mains Light? Yes!

July 29, 2025 by Al Williams 21 Comments

So you want a light that runs off solar power. But you don’t want it to go dark if your batteries discharge. The answer? A solar-mains hybrid lamp. You could use solar-charged batteries until they fall below a certain point and then switch to mains, but that’s not nearly cool enough. [Vijay Deshpande] shows how to make a lamp that draws only the power it needs from the mains.

The circuit uses DC operation and does not feed power back into the electric grid. It still works if the mains is down, assuming the solar power supply is still able to power the lamp. In addition, according to [Vijay], it will last up to 15 years with little maintenance.

The circuit was developed in response to an earlier project that utilized solar power to directly drive the light, when possible. If the light was off, the solar power went to waste. Also, if the mains power failed at night, no light.

The answer, of course, is to add a battery to the system and appropriate switching to drive the lights or charge the battery and only draw power from the mains when needed. Since the battery can take up the slack, it becomes easier to load balance. In periods of low sunlight, the battery provides the missing power until it can’t and then the mains supply takes over.

Comparators determine whether there is an under-voltage or over-voltage and use this information to decide whether the battery charges or if the main supply takes over. Some beefy MOSFETs take care of the switching duties. Overall, a good way to save and reuse solar cell output while still drawing from the grid when necessary.

Small solar lights don’t take much, but won’t draw from commercial power. Solar “generators” are all the rage right now, and you could probably adapt this idea for that use, too.

2025 One Hertz Challenge: Drop The Beat (But Only At 60 BPM)

July 28, 2025 by Adam Zeloof 1 Comment

Mankind has been using water to mark the passage of time for thousands of years. From dripping stone pots in Ancient Egypt to the more mechanically-complicated Greco-Roman Clepsydrae, the history of timekeeping is a wet one — and it makes sense. As an incompressible fluid, water flows in very predictable patterns. If you fill a leaky pot with water and it takes an hour to drain, it will also take an hour the next time you try. One Hertz Challenge entrant [johnowhitaker] took this idea in a different direction, however, with an electromechanical clock that uses dripping water as an indicator.

This clock uses a solenoid to briefly pop the plunger out of a water-filled syringe. This allows a drop to fall from the tip, into a waiting beaker. In addition to the satisfying audio indication this produces, [johnowhitaker] added a bit of food coloring to the dripping water for visual flair. The entire thing is controlled by a Raspberry Pi Pico and a motor driver board, so if you’ve got some spare parts lying about and would like to build your own be sure to head over to the project page and grab the source code.

While this clock isn’t exactly here for a long time (either the syringe will eventually empty or the beaker will overflow), it’s certainly here for a good time. [John] and commenters on his project even have ideas for the next steps: a 1/60 Hz beaker changer, and a 1/600 Hz spill cleaner. Even so, the first couple of drops hitting the beaker produce a lovely lava lamp-esque cloud that is a joy to watch and has us thinking about other microfluidics projects we’ve seen.

And remember — it’s not too late to enter the 2025 One Hertz Challenge!

Models Of Wave Propagation

July 28, 2025 by Al Williams 7 Comments

[Stoppi] always has interesting blog posts and videos, even when we don’t understand all the German in them. The latest? Computer simulation of wave propagation (Google Translate link), which, if nothing else, makes pretty pictures that work in any language. Check out the video below.

Luckily, most browsers will translate for you these days, or you can use a website. We’ve seen waves modeled with springs before, but between the explanations and the accompanying Turbo Pascal source code, this is worth checking out.

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Skateboard Wheels Add Capabilities To Plasma Cutter

July 28, 2025 by Bryan Cockfield 4 Comments

Although firmly entrenched in the cultural zeitgeist now, the skateboard wasn’t always a staple of popular culture. It had a pretty rocky start as surfers jankily attached roller skating hardware to wooden planks searching for wave-riding experiences on land. From those rough beginnings it still took decades of innovation until Rodney Mullen adapted the ollie for flatground skating before the sport really took off. Skateboard hardware is quite elegant now too; the way leaning turns the board due to the shape of the trucks is immediately intuitive for even the most beginner riders, and bearing technology is so high-quality and inexpensive now that skateboard hardware is a go-to parts bin grab for plenty of other projects like this plasma cutter modification.

[The Fabrication Series]’s plasma cutter is mounted to a CNC machine, allowing for many complex cuts in much less time than it would take to do by hand. But cutting tubes is a more complicated endeavor for a machine like this. This is where the skateboard hardware comes in: by fabricating two custom pivoting arms each with two skateboard wheels that push down on a tube to hold it in place, the CNC machine can roll the tube along the table in a precise way as the plasma cutter works through it.

Of course, cutting a moving part is a little more complicated for the CNC machine than cutting a fixed piece of sheet metal, so [The Fabrication Series] walks us through a few ways of cutting pipe for various purposes, including miters and notches. The first step is to build a model of the pipes, in this case using Onshape, and then converting the 3D model of the pipes into a sheet metal model that the CNC machine can use. It does take a few cuts on the machine to fine-tune the cuts, but in no time the machine is effortlessly cutting complex shapes into the pipe. Don’t have a plasma cutter at all? You can always build your own from scratch.

Thanks to [JohnU] and [paulvdh] for the tip!

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Destructive Testing Of ABS And Carbon Fiber Nylon Parts

July 28, 2025 by Maya Posch 9 Comments

PAHT-CF part printed at 45 degrees, with reinforcing bolt, post-failure. (Credit: Functional Print Friday, YouTube)

The good part about FDM 3D printing is that there are so many different filament types and parameters to choose from. This is also the bad part, as it can often be hard to tell what impact a change has. Fortunately we got destructive testing to provide us with some information here. Case in point [Functional Print Friday] on YouTube recently testing out a few iterations of a replacement part for a car.

The original part was in ABS, printed horizontally in a Bambu Lab FDM printer, which had a protruding element snapped off while in use. In addition to printing a replacement in carbon fiber-reinforced nylon (PAHT-CF, i.e. PA12 instead of the typical PA6), the part was now also printed at a 45° angle. To compare it with the original ABS filament in a more favorable way, the same part was reprinted at the same angle in ABS.

Another change was to add a machine screw to the stop element of the part, which turned out to make a massive difference. Whereas the original horizontal ABS print failed early and cleanly on layer lines, the angled versions put up much more of a fight, with the machine screw-reinforced stop combined with the PA12 CF filament maxing out the first meter.

The take-away here appears to be that not only angles are good, but that adding a few strategic metal screws can do wonders, even if you’re not using a more exotic filament type.

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2025 One-Hertz Challenge: Clock Calibrator

July 28, 2025 by Lewin Day 8 Comments

Wall clocks! Are they very accurate? Well, sometimes they are, and sometimes they lose minutes a day. If you’ve got one that needs calibrating, you might like this device from [Lauri Pirttiaho].

Most cheap wall clocks use very similar mechanisms based around the Lavet-type stepper motor. These are usually driven by a chip-on-board oscillator that may or may not be particularly accurate.

[Lauri] desired a way to tune up these cheap clocks by using GPS-level timing accuracy. Thus began a project based around a CY8KIT evaluation board from Cypress. The microcontroller is paired with a small character LCD as a user interface, and hooked up to a cheap GPS module with an accurate 1-pulse-per-second (1PPS) timing output. The concept is simple enough. Clock drift is measured by using counters in the microcontroller to compare the timing of the GPS 1PPS output and the pulses driving the Lavet-type stepper motor. The difference between the two can be read off the device, and used to determine if the wall clock is fast or slow. Then one need only use a trimmer capacitor to tweak the wall clock’s pulse rate in order to make it more accurate.

Few of us spend much time calibrating low-cost wall clocks to high levels of accuracy. If that sounds like a fun hobby to you, or your name is Garrus, you would probably find [Lauri]’s device remarkably useful. Believe it or not, this isn’t the first clock calibrator we’ve seen, either. Meanwhile, if you’ve brewed up your own high-accuracy timing hardware, feel free to let us know on the tipsline.

Be More Axolotl: How Humans May One Day Regrow Limbs And Organs

July 28, 2025 by Maya Posch 26 Comments

Although often glossed over, the human liver is a pretty amazing organ. Not just because it’s pretty much the sole thing that prevents our food from killing us, but also because it’s the only organ in our body that is capable of significant regeneration. This is a major boon in medicine, as you can remove most of a person’s liver and it’ll happily regrow back to its original volume. Obviously this is very convenient in the case of disease or when performing a liver transplant.

Despite tissue regeneration being very common among animals, most mammalian species have only limited regenerative ability. This means that while some species can easily regrow entire limbs and organs including eyes as well as parts of their brain, us humans and our primate cousins are lucky if we can even count on our liver to do that thing, while limbs and eyes are lost forever.

This raises many questions, including whether the deactivation of regenerative capabilities is just an evolutionary glitch, and how easily we might be able to turn it back on.

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