Here’s a simple tip from [Andy], whose Raspberry Pi projects often travel with him outside the workshop: he suggests adding a small HDMI-to-USB video capture device to one’s Raspberry Pi utility belt. As long as there is a computer around, it provides a simple and configuration-free way to view a Raspberry Pi’s display that doesn’t involve the local network, nor does it require carrying around a spare HDMI display and power supply.
The usual way to see a Pi’s screen is to either plug in an HDMI display or to connect remotely, but [Andy] found that he didn’t always have details about the network where he was working (assuming a network was even available) and configuring the Pi with a location’s network details was a hassle in any case. Carrying around an HMDI display and power supply was also something he felt he could do without. Throwing a small HDMI-to-USB adapter into his toolkit, on the other hand, has paid off for him big time.
The way it works is simple: the device turns an HDMI video source into something that acts just like a USB webcam’s video stream, which is trivial to view on just about any desktop or laptop. As long as [Andy] has access to some kind of computer, he can be viewing the Pi’s display in no time.
Many of his projects (like this automated cloud camera timelapse) use the Pi camera modules, so a quick way to see the screen is useful to check focus, preview video, and so on. Doing it this way hit a real sweet spot for him. We can’t help but think that one of these little boards could be a tempting thing to embed into a custom cyberdeck build.
How exactly does salt help? The very fine salt coating deposited on the fibers of a mask’s filtration layer first dissolves on contact with airborne pathogens, then undergoes evaporation-induced recrystallization. Pathogens caught in the filter are therefore exposed to an increasingly-high concentration saline solution and are then physically damaged. There is a bit of a trick to getting the salt deposited evenly on the polypropylene filter fibers, since the synthetic fibers are naturally hydrophobic, but a wetting process takes care of that.
The salt coating on the fibers is very fine, doesn’t affect breathability of the mask, and has been shown to be effective even in harsh environments. The research paper states that “salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%).”
Compound bows (unlike recurve bows, their more mechanically-simple relatives) use a levering system with pulleys and spring tension to grant the user a mechanical advantage. We’re not exactly sure what to call [Zünder’s] bow design. He shared his unconventional take on a DIY bow that uses coiled springs as well as some other unique features.
What we really dig about [Zünder]’s design is how easy it is to grasp how it all works. As he demonstrates using the bow, the way the levers, pulleys, and spring tension all work together is very clear. The 3D-printed quiver and arrow rest are nice added touches, and we especially love the use of three toothbrush heads to provide contained support for a nocked arrow. The ring of bristles are sturdy enough to easily support the shaft, and don’t interfere with the arrow’s fletching.
More people working from home has had an impact on the cost and availability of USB webcams, so [Jeff Geerling] got around the issue with a DIY solution that rang in around $100. It consists of a Raspberry Pi and HQ camera module acting as a USB webcam, and there is no messy streaming of ffmpeg over the network masquerading as a camera device or anything. It works just as a USB camera should.
[Jeff] chose a Raspberry Pi Zero and HQ camera module for his unit, making a tidy package that might not be quite as small as commercial webcams, but is certainly perfectly respectable as a USB camera. That being said, there are a few drawbacks, namely the lack of a microphone or autofocus, latency issues at higher resolutions, and the need to shut down the Pi cleanly.
Check out the GitHub repository for everything needed to set up your own, including a complete hardware list and some options for mounting. [Jeff] also tested whether the camera would work with the new keyboard-embedded Raspberry Pi 400, and it absolutely does. Embedded below is a video walkthrough and demonstration of the whole project, so check it out.
Lacking a DVD drive, [jg] was watching a TV series in the form of a bunch of .avi video files. Of course, when every episode contains a full intro, it is only a matter of time before that gets too annoying to sit through.
The usual method of skipping the intro on a plain video file is a simple one:
Manually drag the playback forward past the intro.
Oops that’s too far, bring it back.
Ugh reversed it too much, nudge it forward.
Okay, that’s good.
[jg] was certain there was a better way, and the solution was using audio fingerprinting to insert chapter breaks. The plain video files now have a chapter breaks around the intro, allowing for easy skipping straight to content. The reason behind selecting this method is simple: the show intro is always 52 seconds long, but it isn’t always in the same place. The intro plays somewhere within the first two to five minutes of an episode, so just skipping to a specific timestamp won’t do the trick.
The first job is to extract the audio of an intro sequence, so that it can be used for fingerprinting. Exporting the first 15 minutes of audio with ffmpeg easily creates a wav file that can be trimmed down with an audio editor of choice. That clip gets fed into the open-source SoundFingerprinting library as a signature, then each video has its audio track exported and the signature gets identified within it. SoundFingerprinting therefore detects where (down to the second) the intro exists within each video file.
Marking out chapter breaks using that information is conceptually simple, but ends up being a bit roundabout because it seems .avi files don’t have a simple way to encode chapters. However, .mkv files are another matter. To get around this, [jg] first converts each .avi to .mkv using ffmpeg then splices in the chapter breaks with mkvmerge. One important element is that the reformatting between .avi and .mkv is done without completely re-encoding the video itself, so it’s a quick process. The result is a bunch of .mkv files with chapter breaks around the intro, wherever it may be!
[Jesse]’s modification doesn’t affect the laser beam itself; it is an improvement on the air assist, which is the name for a constant stream of air that blows away smoke and debris as the laser burns and vaporizes material. An efficient air assist is one of the keys to getting nice clean laser cuts, but [Jesse] points out that a good quality air assist isn’t just about how hard the air blows, it’s also about how smoothly it does so. A turbulent air assist can make scorch marks worse, not better.
As an experiment to improve the quality of the air flowing out the laser nozzle, [Jesse] researched ways to avoid turbulence by creating laminar flow. Laminar flow is the quality of a liquid having layers flowing past one another with little or no mixing. One way to do this is to force liquid through individual, parallel channels as it progresses towards a sharply-defined exit nozzle. While [Jesse] found no reference designs of laminar flow nozzles for air assists, there were definitely resources on making laminar flow nozzles for water. It turns out that interest in such a nozzle exists mainly as a means of modifying Lonnie Johnson’s brilliant invention, the Super Soaker.
Working from such a design, [Jesse] created a custom nozzle to help promote laminar flow. Sadly, a laser cutter head carries design constraints that make some compromises unavoidable; one is limited space, and another is the need to keep the laser’s path unobstructed. Still, after 3D printing it in rigid heat-resistant resin, [Jesse] found a dramatic improvement in the feel of the air exiting the nozzle. Some test cuts confirmed a difference in performance, which results in a noticeably cleaner kerf without scorching around the edges.
One of the things [Nervous System] does is make their own custom puzzles, so any improvement to laser cutting helps reliability and quality. When production is involved, just about everything matters; a lesson [Nervous System] shared when they discussed making the best plywood for creating their puzzles.
This project came up because [Niklas] sometimes found himself working on small projects or experiments that aren’t destined for proper documentation, but nevertheless could benefit from being shared as a photo with a short description. This dovetails with what many social networks offer, except that those platforms also come with other aspects [Niklas] doesn’t particularly want. His online photo diary solves this by having a simple back end with which he can upload, sort, and caption photos in an easy way even from a mobile device.