Interpreters In Scala

July 16, 2021 by Al Williams 15 Comments

You might think of interpreters as only good for writing programs. Many people learned programming on some kind of interpreter — like BASIC — because you get immediate feedback and don’t have to deal with the complexities of a compiler. But interpreters can have other uses like parsing configuration files, for example. [Sakib] has a very complete tutorial about writing an interpreter in Scala, but even if you use another language, you might find the tutorial useful.

We were impressed because the tutorial uses formal parsing using a lexer and a parser. This is how you’d be taught to do it in a computer science class, but not how everyone does it.

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A Cheap Dipole Antenna From An Extension Cord

July 16, 2021 by Al Williams 12 Comments

Dipoles are a classic builder’s antenna, after all they are usually little more than two pieces of wire and a feedline. But as [Rob] shows us in the video below, there are a few things to consider.

The first thing is where to get the wire. A damaged extension cord donated the wire. That’s actually an interesting idea because you get multiple wires the same length inside the extension cord. Continue reading “A Cheap Dipole Antenna From An Extension Cord” →

Final Weekend For Work-From-Home Challenge Of The Hackaday Prize

July 16, 2021 by Mike Szczys No comments

This is the final weekend to enter your work-from-home project in the 2021 Hackaday Prize. We know how much fun it is to be creative with home setups that keep let you work without disrupting your non-work life. Show off what you’ve done and you’ll be in the running for some big cash prizes.

Among the lowest hanging fruit is improving your home’s window to the work world. Anything you can do to make your audio and video experience better on video calls is going to make you happier and make the virtual office feel more like a team. [Andy Lustig] built a dedicated video call control panel that can cut off mic and camera, share his screen, switch views, and leave the meeting. Having always-available physical controls for these is a huge power-up for your cubicle-away-from-the-office.

Long hours hunched over the computer are going to take a toll on your body. There are a number of projects entered in the contest that remind you to take breaks, but [ImageryEel] took at different approach. It’s a wearable posture pack that uses an IMU to measure the position of your spine. You’ll get push notifications when the posture pack notices your upper back is beginning to slump. Hopefully this makes it a self-correcting problem!

Having a cozy place to do you work is great for both your physical and emotional health. [Peter van der Walt] is taking the concept of a home “battlestation” to another level, with a reclining chair design that wraps dual monitors around you as you settle in for the work day.

It’s not too late. Make this weekend into your own mini hackathon and get those entries in by Monday morning. Ten finalists will each receive a $500 cash prize and be in the running for the final round beginning at the end of October. Ultimately, one entry will claim the $25,000 Hackaday Prize along with top prizes for four other finalists.

Begin your project on Hackaday.io today, and use the “Submit Project To” dropdown box in the left sidebar of your project page to enter it in the contest. Good luck!

Making Custom Curved Mirrors At Home

July 16, 2021 by Tom Nardi 8 Comments

Generally speaking, creating custom mirrors is a complex task that involves a lot of careful grinding, and isn’t something to be taken lightly if you need precision results. Just ask the folks who provided NASA with a wonky mirror for the Hubble. But assuming you’re not working on an orbital space telescope (or even a ground based one, for that matter), [volzo] has recently documented some techniques for producing single and double curved mirrors of reasonable quality using common workshop tools.

The first step is finding something that’s a bit easier to work with than glass. After testing various reflective materials such as PVC foil and painted PETG sheets by comparing the reflections of projected test patterns, [volzo] found that laminated polystyrene gave the most accurate results. If you just want to make a simple bent mirror, he shows how you can pop one of these sheets on a CNC router, make the appropriate cuts, and fold them into shape.

That part might seem a bit obvious, but what about a more complex shape? Here, [volzo] points to how the thin sheets of polystyrene also lend themselves to vacuum forming. As demonstrated in the video below, all it takes is a 3D printed plug and some basic equipment to rapidly produce mirrors in arbitrary shapes.

Now obviously the optical properties of such mirrors will leave something to be desired, but depending on your application, that might not be such a big deal. As examples [volzo] shows off a few projects using these custom mirrors, such as a tabletop camera that captures both sides of the table simultaneously and a circular projector. Laminated polystyrene could potentially even be used to create low-cost variable mirrors.

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The Fix Is In: Hubble’s Troubles Appear Over For Now

July 16, 2021 by Dan Maloney 29 Comments

Good news this morning from low Earth orbit, where the Hubble Space Telescope is back online after a long and worrisome month of inactivity following a glitch with the observatory’s payload computer.

We recently covered the Hubble payload computer in some depth; at the time, NASA was still very much in the diagnosis phase of the recovery, and had yet to determine a root cause. But the investigation was pointing to one of two possible culprits: the Command Unit/Science Data Formatter (CU/SDF), the module that interfaces the various science instruments, or the Power Control Unit (PCU), which provides regulated power for everything in the payload computer, more verbosely known as the SI C&DH, or Scientific Instrument Command and Data Handling Unit.

In the two weeks since that report, NASA made slow but steady progress, methodically testing every aspect of the SI C&DH. It wasn’t until just two days ago, on July 14, that NASA made a solid determination on root cause: the Power Control Unit, or more specifically, the power supply protection circuit on the PCU’s 5-volt rail. The circuit is designed to monitor the rail for undervoltage or overvoltage conditions, and to order the SI C&DH to shut down if the voltage is out of spec. It’s not entirely clear whether the PCU is actually putting out something other than 5 volts, or if the protection circuit has perhaps degraded since the entire SI C&DH was replaced in the last service mission in 2009. But either way, the fix is the same: switch to the backup PCU, a step that was carefully planned out and executed on July 15th.

To their credit, the agency took pains that everyone involved would be free from any sense of pressure to rush a fix — the 30-year-old spacecraft was stable, its instruments were all safely shut down, and so the imperative was to fix the problem without causing any collateral damage, or taking a step that couldn’t be undone. And further kudos go to NASA for transparency — the web page detailing their efforts to save Hubble reads almost like a build log on one of our projects.

There’s still quite a bit of work to be done to get Hubble back into business — the science instruments have to be woken up and checked out, for instance — but if all goes well, we should see science data start flowing back from the space telescope soon. It’s a relief that NASA was able to pull this fix off, but the fact that Hubble is down to its last backup is a reminder Hubble’s days are numbered, and that the best way to honor the feats of engineering derring-do that saved Hubble this time and many times before is to keep doing great science for as long as possible.

Just What Have We Become?

July 16, 2021 by Jenny List 69 Comments

The world of open source software is one that often sees disputes between developers, some of which spawn lifelong schisms between devotees of different forks, and others mere storms in a teacup that are settled over a few beers. There are a couple of stories of late though that seem to show the worst in the online world, and which all of us should take a moment to think about.

Many of you may have heard two weeks ago of the passing of [near], the software developer and game translator whose bsnes emulator for the Super Nintendo was the go-to platform for retro Nintendo enthusiasts intent on the pursuit of the closest possible match to the original without possessing real Nintendo hardware. The details of their passing are particularly distressing, in that they committed suicide after numerous attacks over several years from users of Kiwi Farms, a website notorious for the worst kinds of trolling.

Hot on the heels of that distressing story comes news that [Cookie Engineer] is stepping down as maintainer of the project that’s now called Tenacity, a fork of the popular but now-controversial Audacity audio editor. They are doing so after being targeted by users of 4chan, the most well-known of online trolling websites, following an ill-advised Simpsons joke in a naming poll for the software. [Cookie Engineer] alleges that the harassers knocked on doors and windows where they live and a real-world knife attack followed.

Nobody deserves to be hounded to death, to suffer the sort of sustained harassment that [near] encountered, or to be confronted with knife-wielding strangers merely because they have stuck their head above the parapet as an open-source developer. There are no excuses to be made, no justifications for this.

All of us who read Hackaday are likely to be regular users of open-source software, many of us will have used bsnes and may yet use Tenacity, but we probably rarely stop for a moment to think of the real people behind them. Countless hours from innumerable highly-skilled people are what makes the open-source world tick, and aside from the immeasurable sadness of suicide or the horror of a knife attack there can only be harm done to open source software as a whole if to be a prominent developer or maintainer is to expose yourself to this.

The Internet will always have raucous communities at its margins and that’s something which still contributes to its unique culture, but when it jumps off the webpage and into damaging real people then perhaps it has become a monster. As a community we can do so much better, and we shouldn’t be prepared to accept anybody who thinks otherwise among our ranks.

We’d like to remind our readers that help exists for those who have reached the point of considering suicide, and that should you suffer from mental health problems you are not alone in this. Everybody, take care of yourselves, and keep an eye out for each other.

Hackaday Podcast 127: Whippletree Clamps, Sniffing Your Stomach Radio, Multimeter Hum Fix, And C64 Demo; No C64

July 16, 2021 by Mike Szczys No comments

Hackaday editors Mike Szczys and Elliot Williams help you get caught up on a week of wonder hacks. We don’t remember seeing a floppy drive headline the demoscene, but sure enough, there’s a C64 demo that performs after the computer is disconnected. What causes bench tools to have unreliable measurements? Sometimes a poor crystal choice lets AC ruin the party. We dive into the ongoing saga of the Audacity open source project’s change of ownership, and talk about generator exciter circuits — specifically their role in starting grid-scale generators from shutdown.

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!

Direct download (60 MB or so.)