# Kalman Filters Without The Math

If you program using values that represent anything in the real world, you have probably at least heard of the Kalman filter. The filter allows you to take multiple value estimates and process them into a better estimate. For example, if you have a robot that has an idea of where it is via GPS, dead reckoning, and an optical system, Kalman filter can help you better estimate your true position even though all of those sources have some error or noise. As you might expect, a lot of math is involved, but [Pravesh] has an excellent intuitive treatment based around code that even has a collaborative Jupyter notebook for you to follow along.

We have always had an easier time following code than math, so we applaud these kinds of posts. Even if you want to dig into the math, having basic intuition about what the math means first makes it so much more approachable.

# The Simplest Curve Tracer Ever

To a lot of us, curve tracing seems to be one of those black magic things that only the true wizards understand. But as [DiodeGoneWild] explains, curve tracing really isn’t all that complicated, and it doesn’t even require specialized test instruments — just a transformer, a couple of resistors, and pretty much whatever oscilloscope you can lay your hands on.

True to his handle, [DiodeGoneWild] concentrates on the current-voltage curves of Zener diodes in the video below, mainly as a follow-up to his recent simple linear power supply project, where he took a careful look at thermal drift to select the best Zener for the job. His curve tracer is super simple — just the device under test in series with a bunch of 10-ohm resistors and the secondary winding of a 12-volt transformer. The probes of his oscilloscope — a no-frills analog model — go across the DUT and the resistor, and with the scope in X-Y mode, the familiar current-voltage curve appears. Sure, the trace is reversed, but it still provides a good visualization of what’s going on. The technique also works on digital scopes; just be ready for a lot of twiddling to get into X-Y mode and to get the trace aligned.

Of course it’s not just diodes that can be tested with a curve tracer, and [DiodeGoneWild] showed a bunch of other two-lead components on his setup. But for our money, the neatest trick here was using a shorted bridge rectifier to generate a bright spot on the curve to mark the zero crossing point. Clever indeed, and pretty useful on a scope with no graticule.

# The AI Engine That Fits In 100K

Running your own AI models is possible, but it requires a giant computer, right? Maybe not. Researchers at NVidia are showing off Perfusion, a text-to-image model they say is 100KB in size and takes four minutes to train. The model specializes in customizing a photo. For example, the paper shows a picture of a teddy bear and a prompt to dress it as a wizard. In all fairness, the small size and quick training are a little misleading, we think, because the results are still using the usual giant model. What’s small and fast is the customization of the existing model.

Customizing models is a common task since you often want to work with something the model doesn’t contain. For example, you might want to alter a picture of your face or your pet, which probably isn’t in the original model. You can create a special keyword and partially train the model for what you want using something called textual inversion. The problem the researchers identified is that creating textual inversions often causes the new training to leak to unintended areas.

They describe “key locking,” a technique to avoid overfitting when fine-tuning an existing model. For example, suppose you want to add a specific dog picture to the model. With typical techniques, a special keyword like dog* will indicate the custom dog image, but the keyword has no connection with generic dogs, mammals, or animals. This makes it difficult for the AI to work with the image. For example, the prompts “a man sitting” and “a dog sitting” require very different image generations. But if we train a specific dog as “dog*” there’s no deeper understanding that “dog*” is a type of “dog” that the model already knows about. So what do you do with “dog* sitting?” Key locking makes that association.

# Open-Source Firmware For Soldering Irons

For most of us, the first soldering iron we pick up to start working on electronics has essentially no features at all. Being little more than resistive heaters plugged straight into the wall with perhaps a changeable tip, there’s not really even a need for a power switch. But doing anything more specialized than through-hole PCB construction often requires a soldering iron with a little more finesse, though. Plenty of “smart” soldering irons are available for specialized soldering needs now, and some are supported by the open-source IronOS as well.

The project, formerly known as TS100, is a versatile soldering iron control firmware that started as an alternative firmware for only the TS100 soldering iron. It has since expanded to have compatibility with several other soldering irons and hosts a rich set of features, including temperature control, motion activation, and the ability to temporarily increase the temperature when using the iron. The firmware is also capable of working with irons that use batteries as well as irons that use USB power delivery.

For anyone with a modern smart soldering iron, like the Pinecil or various Miniware iron offerings, this firmware is a great way of being able to gain fine control over the behavior of one’s own soldering iron, potentially above and beyond what the OEM firmware can do. If you’re still using nothing more than a 30W soldering iron that just has a wall plug, take a look at a review we did for the TS100 iron a few years ago to see what you’re missing out on.

Photo via Wikimedia Commons

# Microsoft Now Offering Parts And Repair Guides For Xbox Controllers

We’re big fans of repairable hardware here at Hackaday, so much so that when we see a company embracing the idea that their products should actually be serviced rather than thrown in the trash, we like to call attention to it. Yes, that even includes when it’s Microsoft.

This community has had a mixed relationship with the Redmond software giant, to say the least. But we’ve still got to give them credit when they do something positive. Not only are they offering a full selection of replacement parts for both the standard and Elite Xbox controllers, they’ve also provided written instructions and step-by-step video guides on how to install your new parts.

For those of you who stopped playing console games when the controllers still only had two buttons, this might not seem like such a big deal. But considering a new Xbox Elite Wireless Controller will set you back a dizzying \$180, it’s not hard to see why some folks would be excited about the possibility of swapping out the guts of the thing for \$50.

Of course, these parts were already available from third party sellers, and iFixit naturally has repair guides for all the different flavors of Xbox controllers. Nothing about what Microsoft is doing here makes the Xbox controller fundamentally any easier to repair than it was previously. But the fact that the company isn’t treating their customers like adversaries is a step in the right direction.

Valve has been similarly open about the internals of the Steam Deck, though their presentation was a bit dramatic, and even Sony provided an official teardown video for the PS5. We’re not sure why these companies are willing to pull back the curtain when it comes to gaming hardware. Whatever the reason, we’re certainly not complaining.

# Truss-Braced Wings Could Bring New Look To Runways Worldwide

Airliners have looked largely the same for a long time now. The ongoing hunt for efficiency gains has seen the development of winglets, drag reducing films, and all manner of little aerodynamic tricks to save fuel, and hence money.

Boeing now has its eye on bigger, tastier goals. It believes by switching to a truss-braced wing design, it could net double-digit efficiency gains. It’s working together with NASA to see if this concept could change the face of commercial aviation in decades to come.

## Aspect Ratio Matters

The key goal of using a truss-braced wing is to enable an airliner to use a wing much thinner and narrower than usual. These “high aspect ratio” wings are far more efficient than the stubbier, wider wings currently common on modern airliners.  But why is aspect ratio so important, and how does it help

If you’ve ever looked at a glider, you will have noticed its incredibly long and narrow wings, which stand it apart from the shorter, wider wings used on airliners and conventional small aircraft. These wings are said to have a high aspect ratio, the ratio between the square of the wingspan and the projected area of the wing itself.

These wings are highly desirable for certain types of aircraft, as lift-to-drag ratio increases with aspect ratio. Any wing that generates lift also generates some drag, but this can be minimized through careful wing design. By making the wings longer and narrower, and thus higher in aspect ratio, the wing tip vortices generated by the wing are weakened. This reduces drag on the plane, and quite significantly so. Continue reading “Truss-Braced Wings Could Bring New Look To Runways Worldwide”

# Fixing Some More Of Apple’s Design Mistakes

Love them or hate them, there’s no denying that Apple has strayed from the Woz’s original open platform ideal for the Apple II. [Ken Pillonel] is back for another round of fixing Apple’s repairability mistakes with a full complement of 3D printable replacement parts for the AirPods Pro case.

While modeling all of the parts would be handy enough for repairing a device with a 0/10 iFixit score, [Pillonel] modified the parts to go together with screws instead of adhesive so any future repairs don’t require cracking the plastic egg. He says, “By showcasing the potential for repairability, I hope to inspire both consumers and multi-billion dollar companies, like Apple, to embrace sustainable practices in their products.”

[Pillonel]’s repairability exploits may seem familiar to readers from his previous work on adding USB-C to the iPhone and the AirPods Pro case. If you just need to retrieve a lost AirPod, you might try an electromagnet, or you can make a Bluetooth receiver from a pair of knock-off buds.