Custom Smartwatch Makes Diabetes Monitoring Easier For Kids

February 2, 2025 by 21 Comments

Living with Type 1 diabetes is a numbers game. There’s not a moment in the day free from the burden of tracking your blood glucose concentration, making “What’s your number?” a constant question. Technology can make that question easier to ask and answer, but for T1D patients, especially the kids who the disease so often impacts, all that tech can be a distraction.

To solve that problem for his son, [Andrew Childs] built this custom T1D smartwatch. An Apple Watch, which integrates easily into the Dexcom CGM ecosystem, seems an obvious solution, but as [Andrew] points out, strapping something like that on a nine-year-old boy’s wrist is a recipe for disaster. After toying with some prototypes and working out the considerable difficulties of getting a stable BLE connection — the device needs to connect to his son’s iPhone to get CGM data — [Andrew] started work on the physical design.

The watch uses an ESP32-S3 on a custom PCB, as well as a 1.69″ TFT IPS display and a LiPo battery. The board also has an accelerometer for activity monitoring and a vibrator for haptic feedback. Getting all that into a case was no mean feat, especially since some degree of water resistance and shockproofing would be needed for the watch to survive. [Andrew] had a case made by a local 3D printing company, and he managed to source custom-cut and silkscreened glass for the face. The result is remarkably professional-looking, especially for a software developer who hadn’t really stretched his maker wings much before tackling this project.

[Andrew] doesn’t appear to have made build files available yet, although he does say he intends to open-source the project at some point. We look forward to that as it’ll be a big help to anyone trying to hack diabetes care. Until then, if you need a primer on continuous glucose monitoring, we’re happy to oblige.

Tiny RC Four-Wheeler Gets Chassis Upgrade For More Traction

February 2, 2025 by 9 Comments

[Azpaca] purchased a fun little toy car from Tamiya, only… there was a problem. The little off-roader wasn’t up to scratch—despite its four-wheel-drive, it couldn’t get over rough ground to save its life. Thus, it was time to 3D-print a better chassis that could actually get through it!

The problem was quite obvious. With no suspension and a rigid chassis, the vehicle would tend to end up with one or more wheels on the air on rough surfaces. To rectify this, [Azpaca] created a twisting chassis which would allow the wheels to better remain in contact with the ground. The design is relatively straightforward, and reuses much of the original drivetrain, including the simple brushed motor. However, with a pivot right behind the front wheels, it has much more traction on rocks and gravel, and can traverse these terrains much more easily.

Tamiya’s motorized toys aren’t particularly well known in the West, but it’s neat to see the community that exists around modifying them around the world. Design files are available for the curious. If you’re not down with mods, perhaps you’d prefer to print your own cars from scratch. Video after the break.

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Inside A Vintage Oven Controlled Crystal Oscillator

February 1, 2025 by 8 Comments

Crystal oscillators are incredibly useful components, but they come with one little snag: their oscillation is temperature-dependent. For many applications the relatively small deviation is not a problem, but especially for precision instruments this is a deal breaker. Enter the oven controlled crystal oscillator, or OCXO. These do basically what it says on the tin, but what’s inside them? [Kerry Wong] took apart a vintage Toyocom TCO-627VC 10 MHz OCXO, revealing a lot more complexity than one might assume.

Inside the insulated enclosure there is of course the crystal oscillator itself, which has a heating coil wrapped around it. Of note is that other OCXOs that [Kerry] took apart had more insulation, as well as other ways of providing the thermal energy. In this particular unit a thermistor is attached to the crystal’s metal case to measure its temperature and provide feedback to the heating circuit. The ICs on the PCB are hard to identify due to the conformal coating, but at least one appears to be a 74LS00, alongside a 78L05 voltage regulator which reduces the 12V input voltage.

As an older OCXO it probably is a lot chunkier than newer units, but the basic principle remains the same, with a heating loop that ensures that the crystal inside the unit remains at the same temperature.

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Using Microwave Heating To Locally Anneal CNT-Coated FDM Prints

February 1, 2025 by 19 Comments
The CNT coating between the layers is heated with microwaves to locally anneal. (Credit: Sweeney et al., Science Adv., 2017)

Layer adhesion is one of the weak points with FDM 3D printing, with annealing often recommended as a post-processing step. An interestingly creative method for this was published in Science Advances back in 2017, featuring the work of researchers at Texas A&M University and citing previous work by other teams. In the paper by [Charles B. Sweeney] et al, they describe how they coated PLA filament with carbon nanotubes (CNTs), resulting in this CNT being distributed primarily between the individual layers of polymer.

This is useful because CNTs are quite sensitive to microwave radiation, resulting in the conversion to thermal energy, i.e. heat. Compared to traditional annealing where the entire part is placed into an oven or similar, this microwave-based heating – or locally induced RF (LIRF) as they call this method – localizes the heat to the interface between two layers.

The advantages of this approach are that it doesn’t change the dimensions of the part noticeably, it’s faster and more efficient, and the annealing between layers approaches the strength of traditional manufacturing. Unfortunately not too much seems to have happened with this approach since then, but considering that both CNTs (single & double-walled) and microwaves are readily available, there’s not much standing in the way of replicating these results.

Could Non-Planar Infill Improve The Strength Of Your 3D Prints?

February 1, 2025 by 24 Comments

When you’re spitting out G-Code for a 3D print, you can pick all kinds of infill settings. You can choose the pattern, and the percentage… but the vast majority of slicers all have one thing in common. They all print layer by layer, infill and all. What if there was another way?

There’s been a lot of chatter in the 3D printing world about the potential of non-planar prints. Following this theme, [TenTech] has developed a system for non-planar infill. This is where the infill design is modulated with sinusoidal waves in the Z axis, such that it forms a somewhat continuous bond between what would otherwise be totally seperate layers of the print. This is intended to create a part that is stronger in the Z direction—historically a weakness of layer-by-layer FDM parts.

Files are on Github for the curious, and currently, it only works with Prusaslicer. Ultimately, it’s interesting work, and we can’t wait to see where it goes next. What we really need is a comprehensive and scientific test regime on the tensile strength of parts printed using this technique. We’ve featured some other neat work in this space before, too. Video after the break.

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Taking A $15 Casio F91W 5,000 Meters Underwater

February 1, 2025 by 42 Comments

When considering our favorite spy movies and kin that involve deep-sea diving, we’d generally expect to see some high-end watch that costs thousands of dollars and is specially engineered to withstand the immense pressures kilometers below the ocean’s surface. Yet what about a humble Casio F91W that can be bought for about $15 if it’s the genuine article and not one of the millions of fakes? Over at the Watches of Espionage site they figured that they’d dress up one of these famous watches to give it the best possible shot at surviving the crushing pressures at a depth of 5 km.

The actual modification to the F91W was pretty mild, involving nothing but a ‘hydro-mod’ whereby oil is used to replace the air inside the watch case. Since oil is incompressible, nothing bad should happen to the watch. Theoretically at least. The Watch-Under-Test (WUT) was strapped to a US Navy’s CURV 21 remotely operated vehicle and dunked into the ocean before starting its descend into the inky darkness of the deep sea.

Although only hitting a measly 4,950 m, the watch survived just fine, showing that even if you’re a secret US operative on a deep-dive espionage mission, all you really need is one of these Casio watches.

RedBox In The 80s: Meet The VHS Vending Behemoth

February 1, 2025 by 15 Comments

Redbox was a company with a moderately interesting business model—it let you rent DVDs from automated kiosks. It’s an idea so simple it’s almost surprising it didn’t appear sooner. Only, it did—all the way back in the VHS age!

Meet the Video Vendor. YouTuber [SpaceTime Junction] was able to track down one of these rare machines, which apparently formerly served an Ohio rental outlet called Kohnen’s. It’s a monstrous thing that stands taller and about three times wider than traditional vending machines, and it could hold up to 320 tapes in its robotic magazine. It’s got lashings of woodgrain, a green-on-black CRT, and the beautiful kind of clicky keys that went away after the 1980s.

[SpaceTime Junction] has a bunch of videos up on the machine, and you even get to see it powered up.  It’s a little difficult to see what’s going on, because the machine is something like nine feet wide and it’s all shot in vertical video. There isn’t a whole lot of content on these obscurities out there, so this is a great place to start. Apparently, there were recently a hundred or more of these found living in a Texas warehouse according to Reddit, so we might see more of these popping up online soon. [SpaceTime Junction] has toured that facility, too.

You can read more about the fall of Redbox, or the cleanup afterwards, in our prior coverage.

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