Day: January 19, 2018

Linux Fu: Custom Bash Command Completion

January 19, 2018 by 24 Comments

If you aren’t a Linux user and you watch someone who knows what they are doing use Bash — the popular command line interpreter — you might get the impression they type much faster than they actually do. That’s because experienced Linux users know that pressing the tab key will tend to complete what they are typing, so you can type just a few characters and get a much longer line of text. The feature is very smart so you may not have realized it, but it knows a good bit about what you could type. For example, if you try to unzip a file, it knows the expected file name probably has a .zip extension.

How does that happen? At first, you might think, “who cares how it happens?” The problem is when you write a shell script or a program that runs on Linux, the completion gets dumb. Someone has to make Bash smart about each command line program and if you are the author then that someone is you.

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Long-Range RFID Leaflets

January 19, 2018 by 29 Comments

Pick a card, any card. [Andrew Quitmeyer] and [Madeline Schwartzman] make sure that any card you pick will match their NYC art installation. “Replantment” is an interactive art installation which invites guests to view full-size leaf molds casts from around the world.

A receipt file with leaf images is kept out of range in this art installation. When a viewer selects one, and carries it to the viewing area, an RFID reader tells an Arduino which tag has been detected. Solid-state relays control two recycled clothing conveyors draped with clear curtains. The simple units used to be back-and-forth control but through dead-reckoning, they can present any leaf mold cast front-and-center.

Clothing conveyors from the last century weren’t this smart before, and it begs the question about inventory automation in small businesses or businesses with limited space.

We haven’t seen much long-range RFID, probably because of cost. Ordinary tags have been read at a distance with this portable reader though, and NFC has been transmitted across a room, sort of.

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This USB Drive Will Self-Destruct After Ruining Your Computer

January 19, 2018 by 35 Comments

Who would have thought that you could light up pyrotechnics on USB power? This USB keystroke injector that blows up after it’s used proves the concept.

Fully aware that this is one of those “just because you can doesn’t mean you should” projects, [MG] takes pains to point out that his danger dongle is just for dramatic effect, like a prop for a movie or the stage. In fact, he purposely withholds details on the pyrotechnics and concentrates on the keystroke injection aspect, potentially nasty enough by itself, as well as the dongle’s universal payload launching features. We’re a little bummed, because the confetti explosion (spoiler!) was pretty neat.

The device is just an ATtiny85 and a few passives stuffed into an old USB drive shell, along with a MOSFET to trigger the payload. If you eschew the explosives, the payload could be anything that will fit in the case. [MG] suggests that if you want to prank someone, an obnoxious siren might be a better way to teach your mark a lesson about plugging in strange USB drives.

While this isn’t the most dangerous thing you can do with a USB port, it could be right up there with that rash of USB killer dongles from a year or so ago. All of these devices are fun “what ifs”, but using them on anything but your own computers is not cool and possibly dangerous. Watching the smoke pour out of a USB socket definitely drives home the point that you shouldn’t plug in that thumbdrive that you found in the bathroom at work, though.

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DIY Spray Booth Is Both Light And Lit

January 19, 2018 by 17 Comments

Industrial designer [Eric Strebel] has access to big, walk-in spray booths, but bigger isn’t always better. For small jobs, it’s overkill, and he wanted his own spray booth anyway. If you’re ready to upgrade from that ratty old cardboard box in the garage, look no further than [Eric]’s spray booth how-to after the break.

If you don’t already know, [Eric] is something of a foam core legend. He has several videos about model building techniques that produce really slick results, so it’s no surprise to see these skills transfer to a larger build. The booth is built from a single 40″ x 60″ sheet of 1/2″ foam core board, a furnace filter, and a vent fan modified to fit his shop’s system. The whole thing cost less than $200, most of which goes toward the fan.

[Eric] modified an existing spray booth plan to fit his needs and added some really nice touches along the way. All the edges are beveled and the unfinished faces are taped, so at first glance it looks like it’s made out of painted wood or melamine board. The furnace filter slides out one side for easy replacement and is braced with foam scraps so it won’t fall forward. The best part of this booth is the LED strips—they make for way better working conditions than the dim recesses of a cardboard box.

If you’d rather build a walk-in spray booth, why not make your own sliding barn doors, too?

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