Integrating sphere test setup

Cannonball Mold Makes A Dandy Integrating Sphere For Laser Measurements

It’s an age-old riddle: if you have a perfect sphere with a perfectly reflective inner surface, will light bounce around inside it forever? The answer is pretty obvious when you think it through, but that doesn’t mean that you can’t put the principle to use, as we see with this homemade Ulbricht sphere for optical measurements.

If you’ve never heard of an Ulbricht sphere, don’t worry — it’s also known as an integrating sphere, and that makes its function a little more apparent. As [Les Wright] explains, an integrating sphere is an optical element with a hollow spherical cavity that’s coated with a diffusely reflective coating. There are two ports in the sphere, one for admitting light — usually from a laser — and one for light to exit. The light bounces around inside the sphere and becomes perfectly diffuse, and creates a uniform beam at the exit port.

[Les]’ need for an integrating sphere comes from the desire to measure the output of some of his lasers with his Raspberry Pi-based PySpectrometer. Rather than shell out for an expensive commercial integrating sphere, or turn one on a lathe, [Les] turned to an unlikely source: cannonball molds. The inside of the mold was painted with an equally unlikely ultra-white paint concocted from barium sulfate and PVA glue. With a few ports machined into the mold, it works perfectly to diffuse the light from his dye lasers for proper measurements.

Lasers can be an expensive hobby, but [Les] always seems to find a way to make things more affordable and just as good. Whether it’s homemade doorknob caps for high-voltage power supplies or blasting the Bayer filter off a cheap CCD camera, he always seems to find a way.

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Making Something Gorgeous From Framing Lumber

Here at Hackaday, we typically cover things that blink, bleep, and occasionally they might even bloop. However, the name of the site is Hackaday. We’re about being clever, reusing things in new ways, and most importantly celebrating interesting projects. While not a traditional project that would grace the front page, we would argue that this nightstand made from framing lumber clearly belongs.

Framing lumber is infamous for being squirrely, weird, and heavily knotted. Most serious furniture makers avoid using the cheap stuff and opt for more expensive harder woods. Here in the US, the big box hardware stores carry cheap fast-grown soft pine that has significant amounts of warp and twist inherent in the wood. The process of getting it straight with right-angle corners is involved and even once it has been cut, the internal stresses inside the wood are released, rendering the board twisted and warped again over time. The timelapse process of planing, jointing, and cutting in the video has an almost therapeutic aspect to it. The results are two wonderful pieces of useful furniture that would look at home in most rooms.

The craftsmanship evident in the build is noteworthy but more impressive is the process of taking cheap and unfit materials and making something beautiful out of them. Perhaps if you’re inspired and decide to make your own nightstand this weekend, you can add some touch-sensitive electronics to it. Video after the break.

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Hackaday Links: February 6, 2022

Last week, the news was filled with stories of Jack Sweeney and his Twitter-bot that tracks the comings and goings of various billionaires in their private jets. This caught the attention of the billionaire-iest of them all, one Elon Musk, who took exception to the 19-year-old’s feat of data integration, which draws from a number of public databases to infer the location of Elon’s plane. After Jack wisely laughed off Elon’s measly offer of $5,000 to take the bot down, Elon ghosted him — pretty childish behavior for the richest man on the planet, we have to say. But Jack might just have the last laugh, as an Orlando-based private jet chartering company has now offered him a job. Seems like his Twitter-bot and the resulting kerfuffle is a real resume builder, so job-seekers should take note.

Here’s hoping that you have a better retirement plan than NASA. The space agency announced its end-of-life plans for the International Space Station this week, the details of which will just be a run-up to the 2031 de-orbit and crash landing of any remaining debris into the lonely waters of Point Nemo. The agency apparently sees the increasingly political handwriting on the ISS’s aging and sometimes perforated walls, and acknowledges that the next phase of LEO space research will be carried out by a fleet of commercial space stations, none of which is close to existing yet. Politics aside, we’d love to dig into the technical details of the plan, and see exactly what will be salvaged from the station before its fiery demise, if anything. The exact method of de-orbiting too would be interesting — seems like the station would need quite a bit of thrust to put on the brakes, and might need the help of a sacrificial spacecraft.

“You break it, you fix it,” is a philosophy that we Hackaday types are probably more comfortable with than the general public, who tend to leave repairs of broken gear to professionals. But that philosophy seems to be at the core of Google’s new Chromebook repair program for schools, which encourages students to fix the Chromebooks they’re breaking in record numbers these days. Google is providing guidance for schools on setting up complete Chromebook repair facilities, including physical layout of the shop, organization of workflows, and complete repair information for at least a couple of popular brands of the stripped-down laptops. Although the repairs are limited to module-level stuff, like swapping power supplies, we still love the sound of this. Here’s hoping that something like this can trigger an interest in electronics for students that would otherwise never think to open up something as complicated as a laptop.

Back in July, we took note of a disturbing report of an RTL-SDR enthusiast in Crimea who was arrested for treason, apparently based on his interest in tracking flights and otherwise monitoring the radio spectrum. Now, as things appear to be heating up in Ukraine again, our friends at are renewing their warning to radio enthusiasts in the area that there may still be risks. Then as now, we have little interest in the politics of all this, but in light of the previous arrest, we’d say it pays to be careful with how some hobbies are perceived.

And finally, aside from the aforementioned flight-tracking dustup, it’s been a tough week for Elon and Tesla. Not only have 817,000 of the expensive electric vehicles been recalled over something as simple as a wonky seatbelt chime, but another 54,000 cars are also being recalled for a software bug that causes them to ignore stop signs in “Full Self-Driving” mode. We’re not sure if this video of this Tesla hell-ride has anything to do with that bug, but it sure illustrates the point that FSD isn’t really ready for prime time. Then again, as a former Boston resident, we can pretty safely say that what that Tesla was doing isn’t really that much different than the meat-based drivers there.

The Coolest Controller Mod, Hands Down

Video games are a great way to relax, and sometimes get your heart rate up at the same time. But unless you’re playing something like Dance Dance Revolution, the controls pretty much always require the use of both hands. Even the old Atari controller benefited from using the other hand for support.

But what if you don’t have the use of both hands? Or you have a repetitive stress injury? Or you just want to eat cheese curls with chopsticks while you play? [Akaki Kuumeri] has you covered with one of the hands-down greatest uses for 3D printing we’ve seen — a PlayStation DualShock 4 controller modified for one-handed use. If this looks familiar, it may be because [Akaki] made a PS5 controller version a while back, but who can get one of those, anyway?

Though [Akaki] does most of the demonstrating in the video below with their left hand, they were cool enough to make a right-handed version as well. In the left-handed version, the symbol buttons and right trigger are actuated with the left hand, and the right joystick is used by moving the whole controller against your leg, the table, the arm of the couch, or whatever you wish.

[Akaki] even designed some optional pieces, including a leg strap. The right-hand version of course does the D-pad instead. But what should the order of the arrow buttons be? After much contemplation, [Akaki] settled on the standard DDR configuration of ←↓↑→.

We love that the symbols are made from raw filament pressed into grooves, and think it’s totally awesome that this is made to be attached to the controller and removed with one hand. Check out the video below to see it in action with a handful of games.

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No ARM Printer Driver? Just Write Your Own

When you think of the small machines that print the sticky labels on packages, you might not expect to find a complex printer with its own programming language (ZPL). However, [Dan Pastusek] was looking around online and found a small label printer on everyone’s favorite online warehouse for a great price that suggested it supported ZPL. Unfortunately, [Dan] had big dreams for creating a Raspberry Pi-based print station and found the drivers packaged for this particular printer were not ARM compatible. Not quite content to leave it there, he began to chip away at the layers until he had a working driver.

ZPL, at its core, is just a language describing ASCII commands transmitted over a serial connection. So while the printer showed up as an endpoint, it wasn’t working as the filters (the part of the driver that knows how to convert from a PNG to ZPL) was x86 only. On Linux, printer drivers also have a PPD file that describes what a printer can handle in paper size and other settings. The PPD file for the little printer gave the first clue. In the ShortNickName field, it identifies itself as HPRT N41, which is a popular HP printer. So this little printer must be a clone of a printer in that family. Notably, they don’t support ZPL. Instead, the HPRT series support TSPL, another printer language developed by TSC.

This presented a problem as the shipping service that provided the labels that [Dan] was using offered labels in three formats: PNG, PDF, and ZPL. Currently, it does seem like there’s a TSPL to ZPL converter out there for use, so rather than write his own, he took a shortcut and wrote a rasterizer instead. Initially, he tried to use some sample code that he found, and while he got something to come out of the printer, it was blank. So the next test was to save the raw TSPL output from a filer and cat directly to the serial port. This worked amazingly. Next, he wrote a converter to take a PNG and convert them into the bitmap format the TSPL has. The converter is in Javascript as it runs as part of the webserver that manages the print station. Could it be faster in a different language? Sure. But a different language wouldn’t make the printer any faster.

With the addition of a wireless barcode scanner, it’s satisfying to see the print station up and running. Here at Hackaday, we’re no stranger to seeing folks take apart printers to peel back the software and physical layers that make them up.

Two shots of the dispenser in question next to each other, showing it from different sides. One is showing the front panel, and the other shot gives us a better look at the top part, with a rotating disk that has openings for treats to be placed in.

Open-Hardware Dog Treat Dispenser Is A Stepping Stone For Behavioral Research

The principles of open-source hardware are starting to make great strides in scientific research fields. [Walker Arce] tells us about his paper co-authored with [Jeffrey R. Stevens], about a dog treat dispenser designed with scientific researchers in mind – indispensable for behavior research purposes, and easily reproducible so that our science can be, too. Use of Raspberry Pi, NEMA steppers and a whole lot of 3D printed parts make this build cheap (< $200 USD) and easy to repeat for any experiments involving dogs or other treat-loving animals.

Even if you’re not a scientist, you could always build one for your own pet training purposes – this design is that simple and easy to reproduce! The majority of the parts are hobbyist-grade, and chances are, you can find most of the parts for this around your workshop. Wondering how this dispenser works, and most importantly, if the dogs are satisfied with it? Check out a short demonstration video after the break.

Despite such dispensers being commercially available, having a new kind of dispenser designed and verified is more valuable than you’d expect – authors report that, in their experience, off-the-shelf dispensers have 20-30% error rate while theirs can boast just 4%, and they have test results to back that up. We can’t help but be happy that the better-performing one is available for any of us to build. The GitHub repository has everything you could want – from STLs and PCB files, to a Raspberry Pi SD card image and a 14-page assembly and setup guide PDF.

Open hardware and science are a match made in heaven, even if the relationship is still developing. The Hackaday community has come together to discuss open hardware in science before, and every now and then, open-source scientific equipment graces our pages, just like this recent assortment of biosensing hacks using repurposed consumer-grade equipment.

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The Q2, A PDP8-Like Discrete Transistor Computer

[Joe Wingbermuehle] has an interest in computers-of-old, and some past experience of building computers on perfboard from discrete transistors, so this next project, Q2, is a complete implementation of a PDP8-like microcomputer on a single PCB. Like the DEC PDP-8, this is a 12-bit machine, but instead of the diode-transistor logic of the DEC, the substantially smaller Q2 uses a simple NMOS approach. Also, the DEC has core memory, but the Q2 resorts to a pair of SRAM ICs, simply because who wants to make repetitive memory structures with discrete 2N7002 transistors anyway?

SMT components for easy machine placement

Like the PDP-8, this machine uses a bit-serial ALU, which allows the circuit to be much smaller than the more usual ALU structure, at the expense of needing a clock cycle per bit per operation, i.e. a single ALU operation will take 12 clock cycles. For this machine, the instruction cycle time is either 8 or 32 clocks anyway, and at a maximum speed of 80 kHz it’s not exactly fast (and significantly slower than a PDP-8) but it is very small. Small, and perfectly formed.

The machine is constructed from 1094 transistors, with logic in an NMOS configuration, using 10 K pullup resistors. This is not a fast way to build a circuit, but it is very compact. By looking at the logic fanout, [Joe] spotted areas with large fanouts, and reduced the pull-up resistors from 10 K to 1 K. This was done in order to keep the propagation delay within bounds for the cycle time without excessive power usage. Supply current was kept to below 500 mA, allowing the board to be powered from a USB connector. Smart!

Memory is courtesy of two battery-backed 6264 SRAMs, with the four 12-bit general purpose registers built from discrete transistors. An LCD screen on board is a nice touch, augmenting the ‘front panel’ switches used for program entry and user input. A 40-pin header was added, for programming via a Raspberry Pi in case the front panel programming switches are proving a bit tedious and error prone.

Discrete transistor D-type flip flop with indicator. Latest circuit switched to 2N7002 NMOS.

In terms of the project write-up, there is plenty to see, with a Verilog model available, a custom programming language [Joe] calls Q2L, complete with a compiler and assembler (written in Rust!) even an online Q2 simulator! Lots of cool demos, like snake. Game of Life and even Pong, add some really lovely touches. Great stuff!

We’ve featured many similar projects over the years; here’s a nice one, a really small 4-bit one, and a really big one.