TensorFlow In Your Browser

April 16, 2018 by Al Williams 24 Comments

If you want to explore machine learning, you can now write applications that train and deploy TensorFlow in your browser using JavaScript. We know what you are thinking. That has to be slow. Surprisingly, it isn’t, since the libraries use Graphics Processing Unit (GPU) acceleration. Of course, that assumes your browser can use your GPU. There are several demos available, include one where you train a Pac Man game to respond to gestures in your webcam to control the game. If you try it and then disable accelerated graphics in your browser options, you’ll see just what a speed up you can gain from the GPU.

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Two-Cent Temperature Sensors

April 16, 2018 by Elliot Williams 89 Comments

When they need to add temperature control to a project, many hackers reach for a K-type thermocouple for their high-temperature needs, or an integrated temperature-sensing IC when it doesn’t get that hot. The thermocouple relies on very small currents and extremely high gain, and you pretty much need a dedicated IC to read it, which can be expensive. The ICs aren’t as expensive, but they’re basically limited to boiling water. What do you do if you want to control a reflow oven?

There’s a cheaper way that spans a range between Antarctic winter and molten solder, and you’ve probably already got the parts on your shelf. Even if you don’t, it’s only going to run you an extra two cents, assuming that you’ve already got a microcontroller with an ADC in your project. The BOM: a plain-vanilla diode and a resistor.

I’ve been using diodes as temperature sensors in three projects over the last year: one is a coffee roaster that brings the beans up to 220 °C in hot air, another is a reflow hotplate that tops out around 210 °C, and the third is a toner-transfer iron that holds a very stable 130 °C. In all of these cases, I don’t really care about the actual numerical value of the temperature — all that matters is reproducibility — so I never bothered to calibrate anything. I thought I’d do it right for Hackaday, and try to push the humble diode to its limits for science.

What resulted was a PCB fire, test circuits desoldering themselves above 190 °C, temperature probes coming loose, and finally a broken ramekin and 200 °C peanut oil all over my desk. Fun times! On the other hand, I managed to get out enough data to calibrate some diodes, and the results are fantastic. The circuits under test included both best practices and the easiest thing that could possibly work, and the results are pretty close. This is definitely a technique that you want to have under your belt for most temperature ranges. The devil is in the details, of course, so read on!

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Custom Built Vacuum Tube Cassette Player

April 16, 2018 by Tom Nardi 40 Comments

As we’ve said many times here on Hackaday, it’s not our place to question why people make the things they make. There’s a legitimate need or utility for many of the projects we cover, no doubt about it. But there’s also a large number of them which are so convoluted that they border on absurd. Not that we love the crazy ones any less, in fact, we usually like those the best.

So when we saw this incredible modification to a Panasonic RN-404 microcassette recorder which replaces the audio hardware with a custom built vacuum tube amplifier, we didn’t bother asking what the point was. Perhaps it’s an attempt to make the most impractical method for recording and playing back audio, or maybe it was just to see if it was possible. No matter why it was done, it’s here now and it’s absolutely glorious.

If the look of the hardware didn’t tip you off that this project makes use of old Soviet-era components, the video after the break certainly will. Specifically, it’s using 1ZH25R and 1S38A tubes which were originally intended for military use. Just like all cool old Soviet tech was. Say what you will about the Cold War, it certainly got the engineering juices flowing.

There’s quite a bit of information about how these ancient tubes were brought back to life by way of this gorgeous home-etched PCB. Suffice to say, working with tubes is an art to begin with, but working with such small and unique ones is on a whole new level.

This isn’t the first time we’ve seen some tiny tubes make their way into a piece of consumer audio equipment, but this one certainly takes the top spot in terms of professional final results.

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Mechanisms: The Spring

April 13, 2018 by Kristina Panos 64 Comments

Most people probably don’t think about springs until one kinks up or snaps, but most of the world’s springs are pretty crucial. The ones that aren’t go by the name Slinky.

We all use and encounter dozens of different types of springs every day without realizing it. Look inside the world of springs and you’ll find hundreds of variations on the theme of bounce. The principle of the spring is simple enough that it can be extended to almost any shape and size that can be imagined and machined. Because it can take so many forms, the spring as a mechanism has thousands of applications. Look under your car, take apart a retractable pen, open up a stapler, an oven door, or a safety pin, and you’ll find a spring or two. Continue reading “Mechanisms: The Spring” →

Another Reason To Learn Morse Code: Kidnapping

April 13, 2018 by Al Williams 81 Comments

Morse code — that series of dots and dashes — can be useful in the strangest situations. As a kid I remember an original Star Trek episode where an injured [Christopher Pike] could only blink a light once for yes and twice for no. Even as a kid, I remember thinking, “Too bad they didn’t think to teach him Morse code.” Of course odd uses of Morse aren’t just for TV and Movies. Perhaps the strangest real-life use was the case of the Colombian government hiding code in pop music to send messages to hostages.

In 2010, [Jose Espejo] was close to retirement from the Colombian army. But he was bothered by the fact that some of his comrades were hostages of FARC (the Revolutionary Armed Forces of Colombia; the anti-government guerrillas), some for as many as ten years. There was a massive effort to free hostages underway, and they wanted them to know both to boost morale and so they’d be ready to escape. But how do you send a message to people in captivity without alerting their captors?

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Hacking When It Counts: Pigeon-Guided Missiles

April 11, 2018 by Dan Maloney 51 Comments

The image of the crackpot inventor, disheveled, disorganized, and surrounded by the remains of his failures, is an enduring Hollywood trope. While a simple look around one’s shop will probably reveal how such stereotypes get started, the image is largely not a fair characterization of the creative mind and how it works, and does not properly respect those who struggle daily to push the state of the art into uncharted territory.

That said, there are plenty of wacky ideas that have come down the pike, most of which mercifully fade away before attracting undue attention. In times of war, though, the need for new and better ways to blow each other up tends to bring out the really nutty ideas and lower the barrier to revealing them publically, or at least to military officials.

Of all the zany plans that came from the fertile minds on each side of World War II, few seem as out there as a plan to use birds to pilot bombs to their targets. And yet such a plan was not only actively developed, it came from the fertile mind of one of the 20th century’s most brilliant psychologists, and very nearly resulted in a fieldable weapon that would let fly the birds of war.

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Redirected Walking In VR Done Via Exploit Of Eyeballs

April 11, 2018 by Donald Papp 55 Comments

[Anjul Patney] and [Qi Sun] demonstrated a fascinating new technique at NVIDIA’s GPU Technology Conference (GTC) for tricking a human into thinking a VR space is larger than it actually is. The way it works is this: when a person walks around in VR, they invariably make turns. During these turns, it’s possible to fool the person into thinking they have pivoted more or less than they have actually physically turned. With a way to manipulate perception of turns comes a way for software to gently manipulate a person’s perception of how large a virtual space is. Unlike other methods that rely on visual distortions, this method is undetectable by the viewer.

The software essentially exploits a quirk of how our eyes work. When a human’s eyes move around to look at different things, the eyeballs don’t physically glide smoothly from point to point. The eyes make frequent but unpredictable darting movements called saccades. There are a number of deeply interesting things about saccades, but the important one here is the fact that our eyes essentially go offline during saccadic movement. Our vision is perceived as a smooth and unbroken stream, but that’s a result of the brain stitching visual information into a cohesive whole, and filling in blanks without us being aware of it.

Part one of [Anjul] and [Qi]’s method is to manipulate perception of a virtual area relative to actual physical area by making a person’s pivots not a 1:1 match. In VR, it may appear one has turned more or less than one has in the real world, and in this way the software can guide the physical motion while making it appear in VR as though nothing is amiss. But by itself, this isn’t enough. To make the mismatches imperceptible, the system watches the eye for saccades and times its adjustments to occur only while they are underway. The brain ignores what happens during saccadic movement, stitches together the rest, and there you have it: a method to gently steer a human being in a way that a virtual space is larger than the physical area available.

Embedded below is a video demonstration and overview, which mentions other methods of manipulating perception of space in VR and how it avoids the pitfalls of other methods.

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