Tool Demagnetizers And The Magnetic Stray Field

February 23, 2024 by Maya Posch 9 Comments

If you’ve ever found yourself wondering how those tool magnetizer/demagnetizer gadgets worked, [Electromagnetic Videos] has produced a pretty succinct and informative video on the subject.

The magnetizer/demagnetizer gadget after meeting its demise at a cutting disc. (Credit: Electromagnetic Videos, YouTube)

While the magnetizing step is quite straightforward and can be demonstrated even by just putting any old magnet against the screwdriver’s metal, it is the demagnetization step that doesn’t make intuitively sense, as the field lines of the magnets are supposed to align the (usually ferromagnetic) material’s magnetic dipole moments and thus create an ordered magnetic field within the screwdriver.

This is only part of the story, however, as the magnetic field outside of a magnet is termed the demagnetizing field (also ‘stray field’). A property of this field is that it acts upon the magnetization of e.g. ferromagnetic material in a way that reduces its magnetic moment, effectively ‘scrambling’ any existing magnetization.

By repeatedly moving a metal tool through this stray field, each time further and further away from the magnet, the magnetic moment reduces until any magnetization has effectively vanished. It is the kind of simple demonstration of magnetism that really should be part of any physics class thanks to its myriad of real-world uses, as this one toolbox gadget shows.

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ESP32 Oscilloscope Skips Screen For The Browser

February 23, 2024 by Bryan Cockfield 29 Comments

An oscilloscope can be an expensive piece of equipment, but not every measurement needs four channels and gigahertz sampling rates. For plenty of home labs, old oscilloscopes with CRTs can be found on the used marketplace for a song that are still more than capable of getting the job done, but even these can be overpowered (not to mention extremely bulky). If you’re looking for something even cheaper, and quite a bit smaller, this ESP32 scope from [BojanJurca] might fit the bill.

The resulting device manages to keep costs extremely low, but not without a trade-off. For this piece of test equipment, sampling is done over the I2C bus on the ESP32, which can manage a little over 700 samples per second with support for two channels. With the ESP32 connected to a wireless network, the data it captures can be viewed from a browser in lieu of an attached screen, which also keeps the size of the device exceptionally small. While it’s not a speed demon, that’s more than fast enough to capture waveforms from plenty of devices or our own circuit prototypes in a form factor that can fit even the smallest spaces.

Of course for work on devices with faster switching times, it’s always good to keep a benchtop oscilloscope around. But as far as we can tell this one is the least expensive, smallest, and most capable we’ve come across that would work for plenty of troubleshooting or testing scenarios in a pinch. We’ve seen others based on slightly more powerful microcontrollers like this one based on the STM32 and this other built around the Wio Terminal with a SAMD51, both of which also include built-in screens.

A man standing next to a log holds a wooden mallet and a grey froe with a wooden handle. The froe's long straight blade sits atop the end of the log. Several cuts radiate out from the center of the log going through the length of the wood.

Making Wooden Shingles With Hand Tools

February 22, 2024 by Navarre Bartz 23 Comments

While they have mostly been replaced with other roofing technologies, wooden shingles have a certain rustic charm. If you’re curious about how to make them by hand, [Harry Rogers] takes us through his friend [John] making some.

There are two primary means of splitting a log for making shingles (or shakes). The first is radial, like one would cut a pie, and the other is lateral, with all the cuts in the same orientation. Using a froe, the log is split in progressively smaller halves to control the way the grain splits down the length of the log and minimize waste. Larger logs result in less waste and lend themselves to the radial method, while smaller logs must be cut laterally. Laterally cut shingles have a higher propensity for warping and other issues, but will work when larger logs are not available.

Once the pieces are split out of the log, they are trimmed with an axe, including removing the outer sapwood which is the main attractant for bugs and other creatures that might try eating your roof. Once down to approximately the right dimensions, the shingle is then smoothed out on a shave horse with a draw knife. Interestingly, the hand-made shingles have a longer lifespan than those sawn since the process works more with the grain of the wood and introduces fewer opportunities for water to seep into the shingles.

If you’re looking for something more solarpunk and less cottagecore for your house, maybe try a green solar roof, and if you’ve got a glass roof, try cleaning it with the Grawler.

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Spectrum Analyzer Buyer’s Guide

February 21, 2024 by Al Williams 8 Comments

Having a scope in a home lab used to be a real luxury, but these days, its fairly common for the home gamer to have a sophisticated storage scope (or two) hanging around. Dedicated spectrum analyzers are a bit less common, but they have also dropped in price while growing in capabilities. Want to buy your very own spectrum analyzer? [Kiss Analog] has a buyer’s guide for what to consider.

If you’ve already got a scope, it may have a Fast Fourier Transform (FFT) function, and he talks about how it could be used in place of a spectrum analyzer or vice versa. But it really depends on what you’re planning on using it for. If you’re doing compliance testing for emissions, an analyzer is invaluable. If you like building transmitters or even just oscillators for other purposes, viewing the output on a spectrum analyzer can show you how well or poorly your design is performing. Any application where you need to visualize large swaths of the RF spectrum is a candidate for a spectrum analyzer.

Towards the end of the video, you’ll get to see some actual uses on a Uni-T UTS3021B. While those are at the higher end of the hobby price spectrum (no pun intended), it has many features that would have required an instrument ten times that price in years gone by.

There are also some very inexpensive options out there. While it is true, to a degree, that you get what you pay for, it is also true that even these cheap options would be amazing to an engineer from the 1990s. Yes, of course. You could do it with a 555.

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A white man with red hair in pigtails under a brown cap holds an axe with a black head and wooden handle. The axe has a rectangular box welded onto the back side of its trapezoidal head.

Deadblow Axe Splits Wood With Minimal Rebound

February 16, 2024 by Navarre Bartz 17 Comments

Dead-blow hammers are well-known in the construction industry for minimizing rebound. [Jacob Fischer] is on a mission to bring this concept to splitting axes.

Over the course of several months, [Fischer] has been working on adding a dead-blow to a splitting axe. This fifth iteration uses a custom-forged head from blacksmith [Todd Elder] with a dead-blow box welded to the poll. The combination of the head geometry and the dead-blow distributing the delivery of force seems to result in a very effective splitting axe.

The dead-blow portion of the axe is a steel box filled with lead (Pb) BBs. Since the BBs are trailing the axe head within the box, the force from the BBs is delivered later than the initial impact of the steel axe head onto the block of wood, allowing the full force of the blow to be spread out over more time. Dead-blow hammers typically use polymers to further absorb any rebound energy, so there is some limit to the extent rebound can be reduced as seen in the testing portion of the video.

Looking for other ways to split wood? How about this cross-bladed axe or maybe a log splitter or two? If you’re curious about how they used to make axes in the old days, we’ve got you covered there too.

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Change The Jingle In Your Makita Charger Because You Can

February 16, 2024 by Lewin Day 19 Comments

Lots of things beep these days. Washing machines, microwaves, fridge — even drill battery chargers. If you’re on Team Makita, it turns out you can actually change the melody of your charger’s beep, thanks to a project from [Real-Time-Kodi].

The hack is for the Makita DR18RC charger, and the implementation of the hack is kind of amusing. [Real-Time-Kodi] starts by cutting the trace to the buzzer inside the charger. Then, an Arduino is installed inside the charger, hooked up to the buzzer itself and the original line that was controlling it. When it detects the charger trying to activate the buzzer, it uses this as a trigger to play its own melody on the charger instead. The Arduino also monitors the LEDs on the charger in order to determine the current charge state, and play the appropriate jingle for the situation.

It’s an amusing hack, and one that could certainly confuse the heck out of anyone expecting the regular tones out of their Makita charger. It also shows that the simple ways work, too — there was no need to dump any firmware or decompile any code.

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Have A Ball With This 3D Printed Sphere-Making Machine

February 13, 2024 by Dan Maloney 19 Comments

Alright, everyone has 30 seconds to get all the jokes out of their system before we proceed with a look at this 3D printed wooden ball polisher.

Ready?

Theoretically, making a sphere out of any material should be easy. All you need to do is pick a point in space inside the material and eliminate everything more than a specified distance from that point. But in practice, sphere-making isn’t quite so simple. The machine [Fraens] presents in the video below is geared more toward the final polish than the initial forming, with a trio of gear motors set 120 degrees apart driving cup-shaped grinding pads.

Constant pressure on the developing sphere is maintained with a clever triangular frame with springs that pre-load the arms and pull them in toward the workpiece, but stop at the desired radius. The three grinding pads are fitted with sandpaper and constantly turn, wearing down the rough piece until it reaches the final diameter. The machine also supports more aggressive tooling, in the form of hole saws that really get to work on the rough blank. Check it out in the video below.

While we appreciate the fact that this is 3D printed, watching the vibrations it has to endure while the blank is still rough, not to mention all the dust and chips it creates, makes us think this machine might not stand up for long. So maybe letting this circular saw jig cut out a rough ball and using this machine for the final polish would be a good idea. Continue reading “Have A Ball With This 3D Printed Sphere-Making Machine” →