What’s An Exciton?

December 19, 2019 by Al Williams 15 Comments

If you read the scientific literature, you see the familiar subatomic particles you learned about in school: protons, neutrons, and electrons. If you are young enough, you see others you probably heard about, too, like quarks and gluons. But recently there has been a lot of buzz about excitons and even some transistor circuits demonstrated that use them. But what is an exciton?

It actually sounds like a subatomic particle, but it is a little more complicated than that. An exciton is a bound state of an electron and an electron hole and is technically a boson. You are probably familiar with the idea of an electron hole from semiconductor physics. Technically, it is a quasiparticle. The reason scientists are interested in the beast is that it can transport energy without transporting net electric charge. That is, the state itself is neutral, but also contains energy. Continue reading “What’s An Exciton?” →

Prusa Dares You To Break Their Latest Printer

December 16, 2019 by Tom Nardi 158 Comments

Two months after its surprise reveal at the 2019 East Coast RepRap Festival, the Prusa Mini has started shipping out to the first wave of early adopters. True to form, with the hardware now officially released to the public, the company has begun the process of releasing the design as open source. In their GitHub repository, owners can already find the KiCad files for the new “Buddy” control board and STLs for the machine’s printable parts.

But even so, not everyone feels that Prusa Research has made the Mini as “open” as its predecessors. Some concerned owners have pointed out that according to the documentation for the Buddy board, they’ll need to physically snap off a section of the PCB so they can flash custom firmware images via Device Firmware Upgrade (DFU) mode. Once this piece of the board has been broken off, which the documentation refers to as the Appendix, Prusa Research will no longer honor any warranty claims for the electronic components of the printer.

For the hardcore tinkerers out there, this news may come as something of a shock. Previous Prusa printers have enjoyed a fairly active firmware development community, and indeed, features that started out as user-developed modifications eventually made their way into the official upstream firmware. What’s more, certain hardware modifications require firmware tweaks to complete.

Prusa Research explains their stance by saying that there’s no way the company can verify the safety of community developed firmware builds. If thermal runaway protections have been disabled or otherwise compromised, the results could be disastrous. We’ve already seen it happen with other printers, so it’s hard to fault them for being cautious here. The company is also quick to point out that the installation of an unofficial firmware has always invalidated the printer’s warranty; physically breaking the board on the Mini is simply meant as a way to ensure the user understands they’re about to leave the beaten path.

How much support is a manufacturer obligated to provide to a user who’s modified their hardware? It’s of course an issue we’ve covered many times before. But here the situation is rather unique, as the user is being told they have to literally break a piece off of their device to unlock certain advanced functionality. If Prusa wanted to prevent users from running alternate firmware entirely they could have done so (or at least tried to), but instead they’ve created a scenario that forces the prospective tinkerer to either back down or fully commit.

So how did Prusa integrate this unusual feature into their brand new 32-bit control board? Perhaps more importantly, how is this going to impact those who want to hack their printers? Let’s find out.

Continue reading “Prusa Dares You To Break Their Latest Printer” →

Why Is Your Cellphone Not A More Useful Computer?

December 14, 2019 by Jenny List 130 Comments

Sometimes when you are browsing randomly through the tech feeds, up pops an article that just crystallizes a nascent thought that had been simmering below the surface for a long time, and is enough to make you sit up and say “Yes! I agree completely with that!”. Such a moment came with [Cheapscatesguide]’s post: “My Fantasy: A Cellphone I can Use as a Desktop Computer“, in which the pertinent question is asked that if smartphones are so powerful, why are they not much better at being more than, well, smartphones?

Readers with long memories may recall that the cellphone-as-computer idea is one that has been tried at least once before. The Motorola Atrix appeared in the early years of this decade, and was a high-end smartphone that could be slotted into both desktop replacement and netbook-style base stations and used as a Linux-based personal computer. Unfortunately it was both eye-wateringly expensive and disappointingly slow due to a hobbled operating system, so it failed to set the market alight. There was a brief moment when unsold Atrix netbook docks were available on the surplus market and became popular platforms as a Raspberry Pi desktop interface, but this experiment seems to have put paid to the idea of one device to truly rule them all.

If we had to hazard a guess as to why this has failed to happen, we’d finger both the manufacturer’s desire not to undermine their lucrative sales in other sectors, and both their and the carriers’ desire to lock down the devices as much as possible. A manufacturer such as Apple will for example never produce an iPhone that can replace a desktop, because it would affect their MacBook sales. Oddly in another form we’re nearly there, this piece is being worked on with a Chromebook, a device that has a useful browser, a functional Android layer, and (because it’s a 64-bit model) an officially supported and useful Debian layer. We don’t expect this to translate into a phone any time soon though.

From another angle, we’ve asked in the past why we aren’t hacking old cellphones.

Moto Atrix lapdock picture: ETC@USC [CC BY-SA 2.0].

Via Hacker News.

Reflection On A Decade Of Hackerspace Expansion

December 13, 2019 by Jenny List 44 Comments

A few days ago I was invited to a party. Party invites are always good, and if I can make it to this one I’ll definitely go. It’s from a continental European hackerspace, and it’s for their tenth birthday party. As I spent a while checking ferries and flights it struck me, a lot of the spaces in my sphere are about a decade old. I went to London Hackspace’s 10th earlier in the year, and a host of other British hackerspaces aren’t far behind. Something tells me I’ll be knocking back the Club Mate and listening to EDM of some form at more than one such party in the coming year.

For most of the decade since I found the then-recently-established mailing list of my local hackerspace I’ve spent a lot of my time involved in more than one space. I’ve been a hackerspace director, a member, and many roles in between and I’ve seen them in both good times and bad ones. Perhaps it’s time to sit back and take stock of that decade and ask a few questions about hackerspaces. How have they fared, what state are they in now, and where are they going?

Continue reading “Reflection On A Decade Of Hackerspace Expansion” →

This Week In Security: VPNs, Patch Tuesday, And Plundervault

December 13, 2019 by Jonathan Bennett 11 Comments

An issue in Unix virtual private networks was disclosed recently, where an attacker could potentially hijack a TCP stream, even though that stream is inside the VPN. This attack affects OpenVPN, Wireguard, and even IPSec VPNs. How was this possible? Unix systems support all manner of different network scenarios, and oftentimes a misconfiguration can lead to problems. Here, packets sent to the VPNs IP address are processed and responded to, even though they are coming in over a different interface.

The attack initially sounds implausible, as an attacker has to know the Virtual IP address of the VPN client, the remote IP address of an active TCP connection, and the sequence and ACK numbers of that connection. That’s a lot of information, but an attacker can figure it out one piece at a time, making it a plausible attack. Continue reading “This Week In Security: VPNs, Patch Tuesday, And Plundervault” →

Supercon SMD Challenge Gets 3D Printed Probes: Build Your Own

December 12, 2019 by Al Williams 2 Comments

This year was the second SMD challenge at Supercon, so it stands to reason we probably learned a few things from last year. If you aren’t familiar with the challenge, you are served some pretty conventional tools and have to solder a board with LEDs getting progressively smaller until you get to 0201 components. Those are challenging even with proper tools, but a surprising number of people have managed to build them even using the clunky, large irons we provide.

During the first challenge, we did find one problem though. The LEDs are all marked for polarity. However, since we don’t provide super high power magnification, it was often difficult to determine the polarity, especially on the smaller parts. Last year, [xBeau] produced some quick LED testers to help overcome this problem. This year we refined them a bit.

As you can see, the 2018 model was a very clever use of what was on hand. A CR2032 holder powered the probes and the probes themselves were two resistors. If you can get the LED to light with the probes you know which lead is the anode and which is the cathode. A little red ink makes it even more obvious. Continue reading “Supercon SMD Challenge Gets 3D Printed Probes: Build Your Own” →

WWII Aircraft Radio Roars To Life: What It Takes To Restore A Piece Of History

December 12, 2019 by Gregory L. Charvat 59 Comments

I’ve been told all my life about old-timey Army/Navy surplus stores where you could buy buckets of FT-243 crystals, radio gear, gas masks, and even a Jeep boxed-up in a big wooden crate. Sadly this is no longer the case. Today surplus stores only have contemporary Chinese-made boots, camping gear, and flashlights. They are bitterly disappointing except for one surplus store that I found while on vacation in the Adirondacks: Patriot of Lake George.

There I found a unicorn of historical significance; an un-modified-since-WW2 surplus CBY-46104 receiver with dynamotor. The date of manufacture was early-war, February 1942. This thing was preserved as good as the day it was removed from its F4F Hellcat. No ham has ever laid a soldering iron or a drill bit to it. Could this unit have seen some action in the south Pacific? Imagine the stories it could tell!

My unconventional restoration of this radio followed strict rules so as to minimize the evidence of repair both inside and out yet make this radio perform again as though it came fresh off the assembly line. Let’s see how I did.

Continue reading “WWII Aircraft Radio Roars To Life: What It Takes To Restore A Piece Of History” →