Readers who survived the 1970s will no doubt remember the “mood ring” fad, where a liquid crystal mounted to a ring would magically reveal your current emotional state to all and sundry by changing color. This nifty thermochromic display is based on the same principle, and while it might not start a new craze, it’s still pretty mesmerizing to watch.
This isn’t [Moritz v. Sivers]’ first attempt at a thermochromic display. His earlier version was far more complicated, using separate copper plates clad with thermochromic film for each segment, with Peltier devices to cool and heat them individually. Version two is much simpler, using a printed circuit board with heating elements in the shape of seven-segment displays etched into it. The thermochromic film sits directly on the heater PCB; a control PCB below has the MCU and sensors on it. The display alternates between temperature and humidity, with the segments fading in an uneven and ghostly way that really makes this fun to watch. [Moritz] has made the build files available, and there’s a detailed Instructable as well.
As a work of art, solenoid engines are an impressive display of electromagnetics in action. There is limited practical use for them though, so usually they are relegated to that realm and remain display pieces. This one from [Emiel] certainly looks like a work of art, too. It has eight solenoids, mimicking the look and internal workings of a traditional V8.
There’s a lot that has to go on to coordinate this many cylinders. Like an internal combustion engine, it takes precise timing in order to make sure that the “pistons” trigger in the correct order without interfering with each other through the shared driveshaft. For that, [Emiel] built two different circuit boards, one to control the firing of each solenoid and another to give positional feedback for the shaft. That’s all put inside a CNC-machined engine block, complete with custom-built connecting rods and shafts.
If you think this looks familiar, it’s because [Emiel] has become somewhat of an expert in the solenoid engine realm. He started off with a how-to for a single piston engine, then stepped it up with a V4 design after that. That leaves us wondering how many pistons the next design will have. Perhaps a solenoid version of the Volkswagen W12?
It’s often been our experience that some of the most impressive projects are the passion builds, the ones where the builder really put in their all and obsessed over every detail. Even if they don’t always have a practical application, it’s impossible to look at the final product and not respect the accomplishment.
Case in point, this absolutely incredible 3D printed model of a sequential “dogbox” transmission created by [Indeterminate Design]. All of the STL files and a complete bill of materials are available for anyone brave enough to take on the challenge. It might never be mounted to a vehicle and driven around the track, but you can still flick through the gears and watch the complex gearing do its thing.
Even if you don’t want to necessarily build the model itself, [Indeterminate Design] takes you through the concepts behind this unique transmission and how it differs from the sort of gearboxes us lowly commuter drivers are familiar with. He’s even nice enough to explain what a dogbox is.
Put simply, this type of transmission allows the driver to simply move the gear change forward and backwards to step through the gears like in a video game. This prevents you from having to navigate an H-pattern gear shift while dealing with all the other stresses of competition driving. Watching it in action, you can certainly see the appeal.
If you prefer your printed gearboxes to be of the practical variety, we’ve certainly seen plenty of those as well. They’re perfect for next time you need to move an anvil around the shop.
Those who have been suddenly introduced to the wonderful world of working from home over the last couple of weeks may have experienced a bit of culture shock. Even with today’s open floorplan workspaces and less-formal expectations, work isn’t home. That’s especially true with young children in the house, who’ll probably respond to seeing mommy or daddy working from home much differently than [Bob] from accounting would at the office.
To smooth out the rough spots of transitioning to a full-time work-from-home setup, [Brian Lough] threw together this web-enabled “do not disturb” beacon for his office door. The original idea was to simply provide a red light and a green light to let the rest of the family know when [Brian] would be in a meeting, but in an example of scope creep that turned out to be useful, [Mrs. Lough] rewrote the spec to include a button on the family-facing side so that she could alert him that his presence is requested.
[Brian] went through a couple of prototype using both an ESP32 and an ESP8266. We were rooting for the ESP32, which [Brian] was leveraging for its built-in capacitive touch input. That would have eliminated a physical button, but alas, the ESP8266 made it into the final build, along with lots and lots of Blu-Tack. The video below details the build and the code, and features an adorable Irish lesson as a bonus.
Yes, a simple text message would probably have satisfied the specs, but where’s the sport in that? Then again, as [Brian] points out, this build seemed oddly familiar for a good reason.
If you use C or C++, you have probably learned how to open a file and read data from it. Usually, we read a character or a line at a time. At least, it seems that way. The reality is there are usually quite a number of buffers between you and the hard drive, so your request for a character might trigger a read for 2,048 characters and then your subsequent calls return from the buffer. There may even be layers of buffers feeding buffers.
A modern computer can do so much better than reading using things using old calls like fgetc. Given that your program has a huge virtual address space and that your computer has a perfectly good memory management unit within it, you can ask the operating system to simply map the file into your memory space. Then you can treat it like any other array of characters and let the OS do the rest.
The operating system doesn’t necessarily read the entire file in at one time, it just reserves space for you. Any time you hit a page that isn’t in memory, the operating system grabs it for you invisibly. Pages that you don’t use very often may be discarded and reloaded later. Behind the scenes, the OS does a lot so you can work on very large files with no real effort. The call that does it all is mmap.
Hackaday editors Mike Szczys and Elliot Williams undertake a journey through the week of fantastic hacks. Add a new level of complexity to model rockets by launching them from a silo via pneumatic ram before the combustibles even get involved. The eyes of that sculpture are actually following you — and with laser focus! The Game Boy is a pillar of pop culture for a reason, there’s a superb talk that outlines all of the interesting choices that made the electronics so special. We round out the show with a rousing discussion of a space tow truck and a scholarly look at the sporadic wake patter of Alexa et al.
Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!
Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!
Like everyone else, hackers and makers want to do something to help control the spread of COVID-19. The recent posts on Hackaday dealing with DIY and open source approaches to respirators, ventilators, and masks have been some of the most widely read and commented on in recent memory. But it’s important to remember that the majority of us aren’t medical professionals, and that even the most well-meaning efforts can end up making things worse if they aren’t done correctly.
Which is exactly what [Josef Průša] wanted to make clear about 3D printed medical equipment in his latest blog post. Like us, he’s thrilled to see all the energy the maker community is putting into brainstorming ways we can put our unique skills and capabilities to use during this global pandemic, but he also urged caution. Printing out an untested design in a material that was never intended for this sort of application could end up being more dangerous than doing nothing at all.
The nested design lends itself to mass production.
To say that he and his team are authorities in the realm of fused deposition modeling (FDM) would be something of an understatement. They know better than most what the technology is and is not capable of, and they’re of the opinion that using printed parts in respirators and other breathing devices isn’t viable until more research and testing is done
The safest option is to only use printed parts for structural components that don’t need to be sterile. To that end, [Josef] used the post to announce a newly published design of a printable face shield for medical professionals. Starting with an existing open source design, the Prusa Research team used their experience to optimize the headband for faster and easier printing. They can produce four headbands at once on each of the printers in their farm, which will allow them to make as many as 800 shields per day without impacting their normal business operations. The bottleneck on production is actually how quickly they can cut out the clear visors with their in-house laser, not the time it takes to print the frames.
