Weird Lens Allows Light Field Passthrough For VR Headset

August 10, 2023 by 16 Comments

Light Fields are a subtle but critical element to making 3D video look “real”, and it has little to do with either resolution or field of view. Meta (formerly Facebook) provides a look at a prototype VR headset that provides light field passthrough video to the user for a more realistic view of their surroundings, and it uses a nifty lens and aperture combination to make it happen.

As humans move our eyes (or our heads, for that matter) to take in a scene, we see things from slightly different perspectives in the process. These differences are important cues for our brains to interpret our world. But when cameras capture a scene, they capture it as a flat plane, which is different in a number of important ways from the manner in which our eyes work. A big reason stereoscopic 3D video doesn’t actually look particularly real is because the information it presents lacks these subtleties.

Continue reading “Weird Lens Allows Light Field Passthrough For VR Headset” →

Minimizing Stress On A Coin Cell Battery

August 10, 2023 by 20 Comments

When it comes to powering tiny devices for a long time, coin cell batteries are the battery of choice for things like keyfobs, watches, and even some IoT devices. They’re inexpensive and compact and a great choice for very small electricity needs. Their major downside is that they have a relatively high internal resistance, meaning they can’t supply a lot of current for very long without decreasing the lifespan of the battery. This new integrated circuit uses a special DC-DC converter to get over that hurdle and extend the life of a coin cell significantly.

A typical DC-DC converter uses a rapidly switching transistor to regulate the energy flow through an inductor and capacitor, effectively stepping up or stepping down the voltage. Rather than relying on a single converter, this circuit uses a two-stage system. The first is a boost converter to step the voltage from the coin cell up to as much as 11 volts to charge a storage capacitor. The second is a buck converter which steps that voltage down when there is a high current demand. This causes less overall voltage drop on the battery meaning less stress for it and a longer operating life in the device.

There are a few other features of this circuit as well, including an optimizer which watches the behavior of the circuit and learns about the power demands being placed on it. That way, the storage capacitor is only charged up to its maximum capacity if the optimizer determines that much charge is needed. With all of these features a coin cell could last around seven times as long as one using more traditional circuitry. If you really need to get every last bit of energy from a battery, though, you can always use a joule thief.

Myth Tested: DOS Can’t Multitask

August 9, 2023 by 77 Comments

It’s a piece of common knowledge, that MS-DOS wasn’t capable of multitasking. For that, the Microsoft-based PC user would have to wait for the 80386, and usable versions of Windows. But like so many such pieces of received Opinion, this one is full of holes. As [Lunduke] investigates, there were several ways to multitask DOS, and they didn’t all depend on third-party software.

A quick look at DESQview and Concurrent DOS was expected from this article, but of more surprise is that IBM had a multitasking DOS called TopView, or even that Microsoft themselves released the fully multitasking MS-DOS 4.0. We remember DOS 4 as being less than sparkling, but reading the article it’s obvious that we’re thinking of the single-tasking version 4.01.

From 2023 it seems obvious that multitasking is a fundamental requirement of PC use, but surprisingly back in the 1980s a PC was much more a single-application device. On one hand it’s surprising given the number of multitasking DOS products on the market that none of them became mainstream, but perhaps the best evidence of the PC market simply not being ready for it comes in the fact that they didn’t.

If you fancy experimenting with DOS multitasking, at least machines on which to do it can still be found.

Why VR As Monitor Replacement Is Likely To Be Terrible For A While Yet

August 9, 2023 by 26 Comments

Putting on a headset and using virtual monitors in VR instead of physical ones is a use case that pops up, but is it really something feasible? [Karl Guttag], who has long experience and a deep understanding of the technical challenges that face such devices, doesn’t seem to think so.

In his writeup [Karl] often focuses on the recently-unveiled high resolution Apple Vision Pro, but the issues he discusses transcend any particular product. His article is worth the read for anyone with an interest in these issues, but we’ll summarize some main points here. Continue reading “Why VR As Monitor Replacement Is Likely To Be Terrible For A While Yet” →

Pedal Car Vs Ministry Of Transport

August 9, 2023 by 49 Comments

[Tim] from the “Way Out West” Youtube channels has started a fun project — building a wooden pedal-car heavily inspired by “Bugsy Malone”. The kids-sized gangsters in that movie got around in kid-sized pedal cars. Apparently kid-sized [Tim] just loved the idea, but just didn’t have the skills or tools to try to build one. But the time has come, and he has spent years putting together a workshop, tools, and skills.

The goal is a 4-wheeled vehicle that can actually be enclosed, to keep the driver out of the rain. It would be petal powered, with an optional electric assist. It should be made of simple materials, like plywood and epoxy. The design would be freely shared, and the overall cost hopefully kept low. Come back after the link to find the rest of the story, including the monkey wrench thrown into the works.
Continue reading “Pedal Car Vs Ministry Of Transport” →

3D Print Your Own Seiko-Style “Magic Lever” Energy Harvester

August 9, 2023 by 20 Comments

Back in 1956, Seiko created their “magic lever” as an integral part of self-winding mechanical watches, which were essentially mechanical energy harvesters. The magic lever is a type of ratcheting arrangement that ensures a main gear only ever advances in a single direction. [Robert Murray-Smith] goes into detail in this video (here’s a link cued up to 1:50 where he begins discussing the magic lever)

There is a lot of naturally-occuring reciprocal motion in our natural world. That is to say, there is plenty of back-and-forth and side-to-side, but not a lot of round-and-round. So, an effective mechanism for a self-winding watch needed a way to convert unpredictable reciprocal motion into a unidirectional rotary one. The magic lever was one way to do so, and it only has three main parts. [Robert] drew these up into 3D models, which he demonstrates in his video, embedded below.

The 3D models for Seiko’s magic lever are available here, and while it’s fun to play with, [Robert] wonders if it could be integrated into something else. We’ve certainly seen plenty of energy harvesting projects, and while they are mostly electrical, we’ve also seen ideas about how to harvest the energy from falling raindrops.

Continue reading “3D Print Your Own Seiko-Style “Magic Lever” Energy Harvester” →

2023 Hackaday Prize: A Reinvented Solar Tracker

August 9, 2023 by 35 Comments

It probably goes without saying that solar panels need to be pointed at the sun for optimal performance. The tricky bit is that the sun has a funny habit of moving on you. For those with a solar panel on their balcony or garden, mysoltrk tracks the sun to get the most out of a small solar panel.

[Fulvio] built the tracker to be solid, low cost, and sturdy enough to survive outdoors, which is quite a tall order. Low cost meant WiFi and GPS were out. The first challenge was low-cost linear actuators that were 3D printed with a mechanism to lock the shaft. An N20 6 volt 30 RPM geared motor formed the heart of the actuator. Four photo-resistors inside a printed viewfinder detect where the sun is, allowing the system to steer the array to get equal values on all the sensors. An Arduino Nano was chosen as it was low power, low cost, and easy to modify. A L298N h-bridge drives the motors, and a shunt is used instead of limit switches to reduce costs further.

There are a few other clever tricks. A voltage divider reads the power coming off the panel so the circuit doesn’t brown out trying to move the actuators. The load can also be switched off via an IRL540n. As of the time of writing, only the earlier versions of the code are up on GitHub, as [Fulvio] is still working on refining the tracking algorithm. But the actuators work wonderfully. We love the ingenuity and focus on low cost, which probably explains why mysoltrk was selected as a finalist in the 2023 Hackaday Prize Green Hacks challenge.

Continue reading “2023 Hackaday Prize: A Reinvented Solar Tracker” →