Author: Donald Papp

1405 Articles

Everything You Probably Didn’t Know About FOV In HMDs

June 21, 2019 by 8 Comments

VR headsets have been seeing new life for a few years now, and when it comes to head-mounted displays, the field of view (FOV) is one of the specs everyone’s keen to discover. Valve Software have published a highly technical yet accessibly-presented document that explains why Field of View (FOV) is a complex thing when it pertains to head-mounted displays. FOV is relatively simple when it comes to things such as cameras, but it gets much more complicated and hard to define or measure easily when it comes to using lenses to put images right up next to eyeballs.

Simulation of how FOV can be affected by eye relief [Source: Valve Software]
The document goes into some useful detail about head-mounted displays in general, the design trade-offs, and naturally talks about the brand-new Valve Index VR headset in particular. The Index uses proprietary lenses combined with a slight outward cant to each eye’s display, and they explain precisely what benefits are gained from each design point. Eye relief (distance from eye to lens), lens shape and mounting (limiting how close the eye can physically get), and adjustability (because faces and eyes come in different configurations) all have a role to play. It’s a situation where every millimeter matters.

If there’s one main point Valve is trying to make with this document, it’s summed up as “it’s really hard to use a single number to effectively describe the field of view of an HMD.” They plan to publish additional information on the topics of modding as well as optics, so keep an eye out on their Valve Index Deep Dive publication list.

Valve’s VR efforts remain interesting from a hacking perspective, and as an organization they seem mindful of keen interest in being able to modify and extend their products. The Vive Tracker was self-contained and had an accessible hardware pinout for the express purpose of making hacking easier.  We also took a look at Valve’s AR and VR prototypes, which give some insight into how and why they chose the directions they did.

Open Source Headset With Inside-Out Tracking, Video Passthrough

June 15, 2019 by 4 Comments

The folks behind the Atmos Extended Reality (XR) headset want to provide improved accessibility with an open ecosystem, and they aim to do it with a WebVR-capable headset design that is self-contained, 3D-printable, and open-sourced. Their immediate goal is to release a development kit, then refine the design for a wider release.

An early prototype of the open source Atmos Extended Reality headset.

The front of the headset has a camera-based tracking board to provide all the modern goodies like inside-out head and hand tracking as well as the ability to pass through video. The design also provides for a variety of interface methods such as eye tracking and 6 DoF controllers.

With all that, the headset gives users maximum flexibility to experiment with and create different applications while working to keep development simple. A short video showing off the modular design of the HMD and optical assembly is embedded below.

Extended Reality (XR) has emerged as a catch-all term to cover broad combinations of real and virtual elements. On one end of the spectrum are completely virtual elements such as in virtual reality (VR), and towards the other end of the spectrum are things like augmented reality (AR) in which virtual elements are integrated with real ones in varying ratios. With the ability to sense the real world and pass through video from the cameras, developers can choose to integrate as much or as little as they wish.

Terms like XR are a sign that the whole scene is still rapidly changing and it’s fascinating to see how development in this area is still within reach of small developers and individual hackers. The Atmos DK 1 developer kit aims to be released sometime in July, so anyone interested in getting in on the ground floor should read up on how to get involved with the project, which currently points people to their Twitter account (@atmosxr) and invites developers to their Discord server. You can also follow along on their newly published Hackaday.io page.

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Art Project Analyzes Every Public Recording Of Facebook’s CEO Since 2004

June 11, 2019 by 15 Comments

[Benjamin Grosser] had a simple question: “What does Mark Zuckerberg think about?” The resulting art project is named ORDER OF MAGNITUDE and to create it he researched archives of every public utterance the founder and CEO of the world’s largest social media network has made, going as far back as 2004.

The end product is a nearly fifty-minute film consisting entirely of cuts centered around what [Benjamin] says are three of the Facebook CEO’s most favored and often-used terms:

  • The word “more”
  • The word “grow”
  • Metrics such as “ninety-nine percent”, “two million”, and terms of that nature.

The idea is that the resulting video provides insight into what Mark Zuckerberg thinks about, has focused on, and how that has (or has not) changed between 2004 and now.  How well does ORDER OF MAGNITUDE do that? Watch the video below, and judge for yourself.

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A DIY Step Attenuator, By Gluing Together Two Smaller Ones

June 4, 2019 by 4 Comments

In the RF world, attenuators are a useful test and measurement tool. Variable units that can apply different levels of attenuation in discrete steps are even better. [DuWayne] made a 63 dB step attenuator by putting two smaller units in series, with an Arduino Nano in control of them. With a 3D printed enclosure and OLED for feedback, the device is easily adjusted with a single rotary encoder. There was even room to add a micro USB plug for recharging the power supply.

The two smaller digital attenuators [DuWayne] used are essentially breakout boards for the PE4302 digital RF attenuator, and cheaply available from the usual overseas sources. They are capable of up to 31.5 dB of attenuation in 0.5 dB steps, and by using two in series (and controlling them in parallel) [DuWayne] gets a range of up to 63 dB. The design files can be downloaded from a Dropbox share for the project, should you wish to try any of it for yourself.

Are you interested in RF and maybe software defined radio (SDR)? We’ve covered all the stuff you’ll need to get started with an inexpensive RTL-SDR, and sooner or later you may find yourself in need of [Dan Maloney]’s info on cheap and effective dummy loads.

Tiny Two-Digit Thermometer Has Long Battery Life

May 29, 2019 by 20 Comments

Like most of his work, this tiny two-digit thermometer shows that [David Johnson-Davies] has a knack for projects that make efficient use of hardware. No pin is left unused between the DS18B20 temperature sensor, the surface mount seven-segment LED displays, and the ATtiny84 driving it all. With the temperature flashing every 24 seconds and the unit spending the rest of the time in a deep sleep, a good CR2032 coin cell should power the device for nearly a year. The board itself measures only about an inch square.

You may think that a display that flashes only once every 24 seconds might be difficult to actually read in practice, and you’d be right. [David] found that it was indeed impractical to watch the display, waiting an unknown amount of time to read some briefly-flashed surprise numbers. To solve this problem, the decimal points flash shortly before the temperature appears. This countdown alerts the viewer to an incoming display, at the cost of a virtually negligible increase to the current consumption.

[David]’s project write-up explains how everything functions. He also steps through the different parts of the source code to explain how everything works, including the low power mode. The GitHub repository holds all the source files, and the board can also be ordered direct from OSH Park via their handy shared projects feature.

Low power consumption adds complexity to projects, but the payoffs can easily be worth the time spent implementing them. We covered a detailed look into low power WiFi microcontrollers that is still relevant, and projects like this weather station demonstrate practical low power design work.

Gaze Upon This Intricate Victorian-Era Time Lock

May 29, 2019 by 7 Comments

The concept of a time lock is an old one, and here you can see an example of the clockwork and gears version that kept vaults sealed against unauthorized openings. Even if the correct combination was known, these devices prevented opening until a pre-arranged amount of time had passed. The fine folks at [Industrial Alchemy] got a copy of a Yale Triple L mechanical time lock, and like other devices of its kind it required manual winding to function. Since the device as a whole was sealed against tampering, winding and setting was done with a key via the small holes in the front.

These devices were mounted on the inside of a vault door, and worked by mechanically interfacing with the lock mechanism in a variety of different ways depending on make and model. While the time lock was engaged, opening the door was prevented even if the correct combination was used. You may notice the multiple movements; this was for redundancy. The movements were interfaced in a mechanical OR arrangement, meaning that the first one to count down to zero would disengage the time lock. In the case of a malfunction, the backup movements would be responsible for preventing a total lockout — a condition as inconvenient and embarrassing as it would be costly.

Embedded below is a video that focuses on swapping movements in a time lock, but happens to also do a good job of showing off the mechanical design and components. Clockwork was the high technology of its time, and interest in it has seen something of a resurgence now that 3D printing is commonplace.

Continue reading “Gaze Upon This Intricate Victorian-Era Time Lock” →

Loads Of Testing Yields New, Reliable, And Cheap Leather Hardening Technique

May 26, 2019 by 36 Comments

Leather hardening has been around for such a long time that one might think that there was little left to discover, but [Jason F. Timmermans] certainly showed that is not the case. Right around the end of 2018 he set up experiments to compare different techniques for hardening leather, and empirically determine the best options. After considerable effort, he crafted a new method with outstanding results. It’s part of his exhaustive testing of different techniques for hardening leather, including some novel ones. It was a considerable amount of work but [Jason] says that he gathered plenty of really useful information, which we’re delighted that he took the time to share it.

According to [Jason], the various methods of hardening can be separated into four groups:

  1. Thermal: heat-treating at 180 ºF or higher, usually via some kind of boiling or baking process.
  2. Chemical: soaking in a substance that causes changes in the leather. Some examples include ammonia, vinegar, acetone, brine, and alcohol.
  3. Mechanical: hammering the leather.
  4. “Stabilizing” methods: saturating the leather with a substance to add rigidity and strength without otherwise denaturing the leather itself. Examples include beeswax, pine pitch, stearic acid, and epoxy.

We recommend making the time to follow the link in the first paragraph and read the full results, but to summarize: heat-treating generally yields a strong but brittle product, and testing revealed stearic acid  — which resembles a kind of hard, dense wax at room temperature — was an early standout for overall great results. Stearic acid has many modern uses and while it was unclear from [Jason]’s reasearch exactly when in history it became commonplace, at least one source mentioned it as a candidate for hardening leather.

But the story doesn’t stop there. Unsatisfied with simply comparing existing methods, [Jason] put a lot of work into seeing if he could improve things. One idea he had was to combine thermal treatment with a stabilizer, and it had outstanding results. The winning combination (named X1 in his writeup) was to preheat the leather then immerse it in melted stearic acid, followed by bringing the temperature of the combination to 200 ºF for about a minute to heat treat the leather at the same time. [Jason]’s observation was that this method “[B]lew the rest out of the water. Cutting the sample to view the cross section was like carving wood. The leather is very rigid and strong.”

The world may not revolve around leather the way it used to, but there’s still stuff to learn and new things to discover. For example, modern tools can allow for novel takes on old techniques, like using 3D printing to create custom leather embossing jigs.