Ray Tracing On A Modern TI Graphing Calculator

February 21, 2022 by Maya Posch 16 Comments

Something being impractical isn’t any reason not to do it, which is why just about anything with a CPU in it can run Doom by now. For the same reason there obviously is a way to do ray tracing of 3D scenes on a modern-day TI-84 Plus CE graphical calculator. This is excellent news for anyone who has one of these calculators, along with a lot of time, perhaps during boring classes, to spare.

As [TheScienceElf] demonstrates in a video, also embedded after the break, it’s not quite the real-time experience one would expect from an NVidia RTX 30-series GPU. Although the eZ80-based CPU in the calculator is significantly more efficient than a Z80 as found in many 1980s home computers, the demo scene at standard resolution takes about 12 minutes to render, as also noted on the GitHub project page.

Perhaps the most interesting part about this project is its use of the Clang-based C & C++ toolchain for the TI-84 Plus CE which gives easy access to the calculator’s hardware and related, including graphics, file I/O, fonts, keypad input and more. Even if using a TI-84 Plus CE to render the next Pixar-level movie isn’t the most productive use imaginable for these devices, this project and the CE toolchain make it all too easy to tinker with these $150 devices.

It would also offer a nice change of pace from writing Snake in TiBASIC, a BASIC dialect in which [TheScienceElf] incidentally has also written a ray tracer.

(Thanks to [poiuyt] for the tip)

Continue reading “Ray Tracing On A Modern TI Graphing Calculator” →

On the left, four through-hole USB-C connectors laid out on a purple cutting mat. On the right, a teardown picture shows that there's neither resistors nor CC connections inside such a connector, resulting in consequences described in the article.

The USB-C Connectors You Never Knew You Wanted To Avoid

February 20, 2022 by Arya Voronova 24 Comments

On Tech Twitter, some people are known for Their Thing – for example, [A13 (@sad_electronics)], (when they’re not busy designing electronics), searches the net to find outstanding parts to marvel at. A good portion of the parts that they find are outstanding for all the wrong reasons. Today, that’s a through-hole two-pin USB Type-C socket. Observing the cheap tech we get from China (or the UK!), you might conclude that two 5.1K pulldown resistors are very hard to add to a product – this socket makes it literally impossible.

We’ve seen two-pin THT MicroUSB sockets before, sometimes used for hobbyist kits. This one, however, goes against the main requirement of Type-C connectors – sink (Type-C-powered) devices having pulldowns on CC pins, and source devices (PSUs and host ports) having pull up resistors to VBUS. As disassembly shows, this connector has neither of these nor the capability for you to add anything, as the CC pins are physically not present. If you use this port to make a USB-C-powered device, a Type-C-compliant PSU will not give it power. If you try to make a Type-C PSU with it, a compliant device shall (rightfully!) refuse to charge from it. The only thing this port is good for is when a device using it is bundled with a USB-A to USB-C cable – actively setting back whatever progress Type-C connectors managed to make.

As much as USB Type-C basics are straightforward, manufacturers get it wrong on the regular – back in 2016, a wrong cable could kill your $1.5k MacBook. Nowadays, we might only need to mod a device with a pair of 5.1K resistors every now and then. We can only hope that the new EU laws will force devices to get it right and stop ruining the convenience for everyone, so we can finally enjoy what was promised to us. Hackers have been making more and more devices with USB-C ports, and even retrofitting iPhones here and there. If you wanted to get into mischief territory and abuse the extended capabilities of new tech, you could even make a device that enumerates in different ways if you flip the cable, or make a “BGA on an FPC” dongle that is fully hidden inside a Type-C cable end!

All About Dichroic Optical Filters

February 20, 2022 by Dave Rowntree 7 Comments

[IMSAI Guy] presents for your viewing pleasure, a nice video on the topic of optical filters and mirrors. (Video, embedded below) The first optical device is a simple absorption filter, where incoming light is absorbed in a wavelength-selective manner. Much more interesting however is the subject of interference or dichroic filters. These devices are constructed from many thin layers of a partially reflective material, and operate on the principle of interference. This means that photons hitting the filter stack will interfere either constructively or destructively giving the filter a pass or stop response for a particular wavelength.

As [IMSAI Guy] demonstrates, this makes the filters direction-specific, as photons hitting the stack at a different angle will travel slightly further. Longer travel means the interference effect will be different, and so will the filtering response. You can see this by playing around with one in your hands and seeing the color change as your rotate it. Dichroic filter films can also make for some stunning optical effects. Very cool stuff.

By creating a filter stack with a wide enough range of inter-layer thicknesses, it’s possible to construct a mirror that covers the full spectrum with excellent reflectivity. Since you can tune the layers, you can make it reflect any range of wavelengths you like. One thing we’ve not seen before is a wedge-like optical filter device, where the layer thicknesses progressively increase lengthways, creating a variable optical frequency response along the length. We guess this would be useful for diagnostics in the field, or perhaps for manually tuning a beam path?

We like the applications for dichroic films – here’s an Infinity Mirror ‘Hypercrystal’. If you don’t want to buy off-the-shelf films, perhaps you could sputter yourself something pretty?

Continue reading “All About Dichroic Optical Filters” →

The inside of a Laser-Induced Breakdown Spectrometer

Spectrometer Detects Chemicals By Zapping Samples With A Laser Beam

February 19, 2022 by Robin Kearey 18 Comments

Here at Hackaday, we love projects that result in useful lab equipment for a fraction of the cost of professional gear. [Lorenz], over at Advanced Tinkering, built his own instrument for Laser-Induced Breakdown Spectroscopy, or LIBS, and it’s quite an impressive device. LIBS is a technique for analyzing substances to find their chemical composition. Basically, the idea is to zap a sample with a powerful laser, then look at the little cloud of plasma that results and measure the wavelengths emitted by it.

A plot showing the spectrum of hematite — The spectrum of hematite (iron oxide), compared to that of pure iron

The laser [Lorenz] used is a Nd:YAG unit salvaged from a tattoo removal machine. After it fires a pulse, a photodiode detects the light and triggers a spectrometer, which consists of a diffraction grating, a few lenses and mirrors, and a linear CCD sensor. The grating splits the incoming lights into its constituent components, which fall onto the CCD and trigger its pixels. An STM32 Nucleo board reads out the results and sends them to a PC for further processing.

That processing bit turned out to be a full project on its own. [Lorenz] called upon [g3gg0], who software that simplifies the operation of the spectrometer. First, it helps with the instrument’s calibration. Point the detector at a well-known light source like a laser or a fluorescent lamp, then select the expected wavelengths on the resulting spectral plot. The software then automatically calculates the correct coefficients to map each pixel to a specific wavelength.

The software also contains a database of spectra corresponding to chemical elements: once you’ve taken a spectrum of an unknown sample, you can overlay these onto the resulting plot and try to find a match. The resulting system seems to work quite well. Samples of iron oxide and silver oxide gave a reasonable match to their constituent components.

We’ve seen other types of spectrometers before: if you simply want to characterize a light source, check out this Raspberry Pi-based model. If you’re interested in chemical analysis you might also want to look at this open-source Raman spectrometer.

Continue reading “Spectrometer Detects Chemicals By Zapping Samples With A Laser Beam” →

Building A High-Capacity Linear Servo Actuator

February 17, 2022 by Lewin Day 19 Comments

Linear actuators are useful things, moving things in straight lines rather than annoying circles like so many motors. [Retsetman] recently built a linear servo actuator of his own design with accurate positional control.

The design relies on a carriage that moves along a threaded rod, perhaps the most rudimentary design of linear actuator. A large brushed DC motor is used to turn the threaded rod through a 3D-printed 9:1 herringbone geartrain, shifting the actuator back and forth. End stop switches are used to disengage the motor to avoid damage to the mechanism. Feedback is via a ten-turn potentiometer driven off the output geartrain to match the range of the actuator to the rotational range of the pot.

The final build has a stroke of approximately 100 mm, and can lift and hold a 15 kg weight with ease. In a pull test, the actuator failed at a load just shy of 100 kg. If you’re looking for something smaller, though, you can try building a linear actuator out of old DVD drive parts instead. Video after the break.

Continue reading “Building A High-Capacity Linear Servo Actuator” →

Infinity Mirror Hypercrystal Is As Beautiful As It Sounds

February 17, 2022 by Lewin Day 4 Comments

Sometimes, we feature projects that are full to the brim with advanced functionality or solve some tricky little problem for the end-user. Other times, we feature stuff that just looks super damn cool, and the Infinity Mirror Hypercrystal is firmly in that latter category.

This show-stopping build comes to us from [Inanna Malick], who put together the design using algorithmic and generative art techniques she’s been working on for years. The form is a non-symmetrical, non-platonic solid, with each of its eight faces laser cut from mirrored acrylic. Plywood sections are used to hold together the structure.

Initially, the build was illuminated from within by white LEDs, but [Inanna] wasn’t satisfied with the look, which was too rooted in regular human technology. They were instead covered up with transparent dichroic tape, creating the lurid shifting colors that do so much to add to the mystery of the legendary Hypercrystal.

The result is an infinity mirror piece that looks more advanced, more alien, and more luridly enticing than most we’ve ever seen. The dichroic shift placed on the LEDs goes a long way to elevating this sculpture to new aesthetic heights. Video after the break.

Continue reading “Infinity Mirror Hypercrystal Is As Beautiful As It Sounds” →

Anti-Curl Sandpaper Storage Is Impressive

February 15, 2022 by Kristina Panos 15 Comments

Maybe it’s the humidity, maybe it’s the cold weather. Something is making [Laura Kampf]’s nice fabric-backed sandpaper curl up into scrolls the second it comes out of the package. So you can understand why she urgently wanted to make a storage system that would be easy to flip through like a record bin, but also provide enough pressure to keep the papers flat.

Although [Laura] didn’t know what exactly the end result would be, she got started on it anyway — that’s a great way to get more projects off the drawing board and past the finish line. It worked out, because she got a great idea while building the box and using nice cam clamps to hold the finger joints together as the glue dried. Since she already had a bunch of these cam clamps in different lengths lying around, why not use a couple of them for this?

[Laura] has two major classifications of sandpaper — paper-backed and fabric-backed — and built them separate boxen using two clamps for each box. She joined the pins with a DIY handle in order to move the cams in unison, so all she has to do is pull out to flip through the papers, and push the handle back and down to re-pressurize the stack for storage. Be sure to check out the build and demo video after the break.

While DIY clamps are often wood and metal affairs, it’s good to have 3D printing in your corner.

Continue reading “Anti-Curl Sandpaper Storage Is Impressive” →