Ask Hackaday: Is USB Robust Enough?

April 29, 2019 by Mike Szczys 60 Comments

Earlier this month a single person pleaded guilty to taking down some computer labs at a college in New York. This was not done by hacking into them remotely, but by plugging a USB Killer in one machine at a time. This malicious act caused around $58,000 in damage to 66 machines, using a device designed to overload the data pins on the USB ports with high-voltage. Similar damage could have been done with a ball-peen hammer (albeit much less discreetly), and we’re not here to debate the merits of the USB Killer devices. If you destroy property you don’t own you should be held accountable.

But the event did bring an interesting question to mind. How robust are USB ports? The USB Killer — which we’ve covered off and on through the years — is billed as a “surge testing” device and operates by injecting -200 volts DC on the data lines of the USB connection. Many USB ports are not protected against this and the result is permanent damage to the computer hardware. Is protection for these levels of abuse necessary or would it needlessly add cost to our machines?

A chip like the TPD4S014 has ESD protection on the data lines that is rated up to +/- 1500 volts, clamping to ground to dissipate the energy. It’s a solution that should protect against repeated spikes on the data lines, as well as short circuits on the power lines and over/undervoltage situations.

The ADuM4160 is an interesting step up from this. It’s designed to provide isolation between a USB host and the device connected to it. Rather than relying on clamping, this chip implements isolation through air core transformers. Certainly this would be overkill to install in every product, but for those of use building and testing USB devices this would save you from “Oops, wrong USB cable” moments at the work bench.

Speaking of accidents at the bench, there is certainly a demand for USB isolation outside of what’s built into our computers. Earlier this year we saw a fantastic take on a properly-designed USB power strip. Among the goals were current limiting, undervoltage protection, and a proper power disconnect switch for each port. The very need to design your own reminds us that consumer manufacturers are often lazy in their USB design. “Use a USB hub” is bad advice for protection at the workbench since quality of design varies so wildly.

We would be interested in hearing from anyone who has insight on standards applying to equipment continuing to survive over current or over voltage events and remain functional. There are standards like UL-60950 that should apply to USB. But that standard includes language about failing safe for the operator, not necessarily remaining functional:

After abnormal operation or a single fault (see 1.4.14), the equipment shall remain safe for an OPERATOR in the meaning of this standard, but it is not required that the equipment should still be in full working order. It is permitted to use fusible links, THERMAL CUT-OUTS, overcurrent protection devices and the like to provide adequate protection.

So, we’re here to ask you, the readers of Hackaday. Are our USB devices robust enough? Do you have a go-to USB protection chip, part, or other circuit you like to use? Have you ever accidentally killed a USB host device (if so, how)? Do you have special equipment that you depend on when developing projects involving USB? Let us know what you think in the comments below.

Parametric Amplifiers And Varactors

April 26, 2019 by Al Williams 9 Comments

It is hard to imagine a time without active amplification. However, if you go back far enough, radio communications started in an era where generating RF required something like a spark gap and reception was only possible if the signal was strong enough at the antenna — like with a crystal radio. It would be a few years before tubes allowed both transmitted and receiving signals to be electronically amplified and longer still before transistors that would work at radio frequency appeared. However, even active devices have had their limitations and the parametric oscillator and amplifier are ways around some of those problems.

These were more popular in the 1970s when it was harder to get transistors that would work at very high frequencies. They are still useful when you need very low noise amplification. In addition, the same effect is used in optical devices and you can even observe the effect in mechanical devices.

What Is It Exactly?

The phrase parametric means that the amplification or oscillation occurs because of the change in a parameter of the system. A simple example would be a variable capacitor. We know the charge in a capacitor is equal to the capacitance times the voltage across the unit. That also implies that, if charge is known, we can know the voltage by dividing the charge by the capacitance. To put it in numerical terms, if a 0.1 farad capacitor has 12V across it, the charge is 1.2 coulombs. Suppose our input signal is 12V and we let the capacitor charge up to that value. Then we twist the capacitor’s knob to give it a value of 0.05 farad. The charge can’t change, so now we have 24 volts across the capacitor. That’s an amplification of 2 times. These values, of course, are not practical. Nor is it practical to twist a capacitor knob constantly to amplify. However, it is a good analog of how a parametric amplifier works.

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Retrotechtacular: Balloons Go To War

April 25, 2019 by Tom Nardi 5 Comments

To the average person, the application of balloon technology pretty much begins and ends with birthday parties. The Hackaday reader might be able to expand on that a bit, as we’ve covered several projects that have lofted various bits of equipment into the stratosphere courtesy of a high-altitude balloons. But even that is a relatively minor distinction. They might be bigger than their multicolored brethren, but it’s still easy for a modern observer to write them off as trivial.

But during the 1940’s, they were important pieces of wartime technology. While powered aircraft such as fighters and bombers were obviously more vital to the larger war effort, balloons still had numerous defensive and reconnaissance applications. They were useful enough that the United States Navy produced a training film entitled History of Balloons which takes viewers through the early days of manned ballooning. Examples of how the core technology developed and matured over time is intermixed with footage of balloons being used in both the First and Second World Wars, and parallels are drawn to show how those early pioneers influenced contemporary designs.

Even when the film was produced in 1944, balloons were an old technology. The timeline in the video starts all the way back in 1783 with the first piloted hot air balloon created by the Montgolfier brothers in Paris, and then quickly covers iterative advancements to ballooning made into the 1800’s. As was common in training films from this era, the various “reenactments” are cartoons complete with comic narration in the style of W.C. Fields which were designed to be entertaining and memorable to the target audience of young men.

While the style might seem a little strange to modern audiences, there’s plenty of fascinating information packed within the film’s half-hour run time. The rapid advancements to ballooning between 1800 and the First World War are detailed, including the various instruments developed for determining important information such as altitude and rate of climb. The film also explains how some of the core aspects of manned ballooning, like the gradual release of ballast or the fact that a deflated balloon doubles as a rudimentary parachute in an emergency, were discovered quite by accident.

When the film works its way to the contemporary era, we are shown the process of filling Naval balloons with hydrogen and preparing them for flight. The film also talks at length about the so-called “barrage balloons” which were used in both World Wars. Including a rather dastardly advancement which added mines to the balloon’s tethers to destroy aircraft unlucky enough to get in their way.

This period in human history saw incredible technological advancements, and films such as these which were created during and immediately after the Second World War provide an invaluable look at cutting edge technology from a bygone era. One wonders what the alternative might be for future generations looking back on the technology of today.

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The $50 Ham: Dummy Loads

April 25, 2019 by Dan Maloney 41 Comments

This is an exciting day for me — we finally get to build some ham radio gear! To me, building gear is the big attraction of amateur radio as a hobby. Sure, it’s cool to buy a radio, even a cheap one, and be able to hit a repeater that you think is unreachable. Or on the other end of the money spectrum, using a Yaesu or Kenwood HF rig with a linear amp and big beam antenna to work someone in Antartica must be pretty cool, too. But neither of those feats require much in the way of electronics knowledge or skill, and at the end of the day, that’s why I got into amateur radio in the first place — to learn more about electronics.

To get my homebrewer’s feet wet, I chose perhaps the simplest of ham radio projects: dummy loads. Every ham eventually needs a dummy load, which is basically a circuit that looks like an antenna to a transmitter but dissipates the energy as heat instead of radiating it an appreciable distance. They allow operators to test gear and make adjustments while staying legal on emission. Al Williams covered the basics of dummy loads a few years back in case you need a little more background.

We’ll be building two dummy loads: a lower-power one specifically for my handy talkies (HTs) will be the subject of this article, while a bigger, oil-filled “cantenna” load for use with higher power transmitters will follow. Neither of my designs is original, of course; borrowing circuits from other hams is expected, after all. But I did put my own twist on each, and you should do the same thing. These builds are covered in depth on my Hackaday.io page, but join me below for the gist on a good one: the L’il Dummy.

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Radio Piracy On The High Seas: Commercial Demand For Taboo Music

April 24, 2019 by Al Williams 32 Comments

The true story of pirate radio is a complicated fight over the airwaves. Maybe you have a picture in your mind of some kid in his mom’s basement playing records, but the pirate stations we are thinking about — Radio Caroline and Radio Northsea International — were major business operations. They were perfectly ordinary radio stations except they operated from ships at sea to avoid falling under the jurisdiction of a particular government.

Back then many governments were not particularly fond of rock music. People wanted it though, and because people did, advertisers wanted to capitalize on it. When people want to spend money but can’t, entrepreneurs will find a way to deliver what is desired. That’s exactly what happened.

Of course, if that’s all there was to it, this wouldn’t be interesting. But the story is one of intrigue with armed boardings, distress calls interrupting music programs, and fire bombings. Most radio stations don’t have to deal with those events. Surprisingly, at least one of these iconic stations is still around — in a manner of speaking, anyway.

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3D Printering: The Quest For Printable Food

April 24, 2019 by Tom Nardi 44 Comments

A video has been making the rounds on social media recently that shows a 3D printed “steak” developed by a company called NovaMeat. In the short clip, a machine can be seen extruding a paste made of ingredients such as peas and seaweed into a shape not entirely unlike that of a boot sole, which gets briefly fried in a pan. Slices of this futuristic foodstuff are then fed to passerby in an effort to prove it’s actually edible. Nobody spits it out while the cameras are rolling, but the look on their faces could perhaps best be interpreted as resigned politeness. Yes, you can eat it. But you could eat a real boot sole too if you cooked it long enough.

To be fair, the goals of NovaMeat are certainly noble. Founder and CEO Giuseppe Scionti says that we need to develop new sustainable food sources to combat the environmental cost of our current livestock system, and he believes meat alternatives like his 3D printed steak could be the answer. Indeed, finding ways to reduce the consumption of meat would be a net positive for the environment, but it seems his team has a long way to go before the average meat-eater would be tempted by the objects extruded from his machine.

But the NovaMeat team aren’t the first to attempt coaxing food out of a modified 3D printer, not by a long shot. They’re simply the most recent addition to a surprisingly long list of individuals and entities, not least of which the United States military, that have looked into the concept. Ultimately, they’ve been after the same thing that convinced many hackers and makers to buy their own desktop 3D printer: the ability to produce something to the maker’s exacting specifications. A machine that could produce food with the precise flavors and textures specified would in essence be the ultimate chef, but of course, it’s far easier said than done.

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Need A Small Keyboard? Build Your Own!

April 23, 2019 by Brian Benchoff 72 Comments

If you want keyboards, we can get you keyboards. If you want a small keyboard, you might be out of luck. Unless you’re hacking Blackberry keyboards or futzing around with tiny tact switches, there’s no good solution to small, thin, customization keyboards. There’s one option though: silicone keyboards. No one’s done it yet, so I figured I might as well.

Unfortunately, there is no readily available information on the design, construction, or manufacture of custom silicone keypads. There is a little documentation out there, but every factory that does this seems to have copy and pasted the information from each other. Asking a company in China about how to do it is a game of Chinese Whispers. Despite this, I managed to build a custom silicone keypad, and now I’m sharing this information on how to do it with you.

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