Bonsai LED Matrix Has Chaotic Roots

October 21, 2020 by 4 Comments

Most people don’t hand solder their surface mount LED matrices these days, and they certainly don’t do it with RGB LEDs. [fruchti] isn’t most people, has managed to grow his electronic hobby into the art form know as Bonsai.

The organic shapes of miniature trees grown over the course of decades is the ultimate indicator of patience and persistence. For those who prefer bending copper to their will rather than saplings, producing an LED tree that looks and functions this well is an accomplishment that signals clever planning and patient fabrication. The animated result is a masterpiece that took about eighteen months to complete.

There are 128 enamel-coated wires that twist into branches holding 32 RGB light-emitting diodes. Tapping into each at the base of the tree is a chaotic mess made a bit easier by a cleverly designed circuit board.

A circular petal pattern was laid out in Inkscape that includes a hole at the center for the “trunk” to pass through. The LED matrix is designed with 8 rows and 12 columns, but 24 pads were laid out so that only four wires would need to be soldered to each copper petal. Even so, look at the alligator clip holding up this PCB to get an idea of the scale of this job!

The angular base is itself made of copper clad board soldered on the inside of the seams and painted black on the outside. This hides the “petal” PCB, as well as a breakout board for an STM32 microcontroller and a power management circuit that lets you use your choice of USB or a lithium battery.

We wonder if [fruchti] has thought about adding some interactivity to his sapling. While we haven’t seen such a beautiful, tiny, creation as this, we have seen an LED tree whose lights can be blown out like birthday candles. Wouldn’t this be an excellent entry in our Circuit Sculpture challenge? There’s still a few weeks left!

Taking A Crack At The Traveling Salesman Problem

October 21, 2020 by 16 Comments

The human mind is a path-planning wizard. Think back to pre-lockdown days when we all ran multiple errands back to back across town. There was always a mental dance in the back of your head to make sense of how you planned the day. It might go something like “first to the bank, then to drop off the dry-cleaning. Since the post office is on the way to the grocery store, I’ll pop by and send that box that’s been sitting in the trunk for a week.”

This sort of mental gymnastics doesn’t come naturally to machines — it’s actually a famous problem in computer science known as the traveling salesman problem. While it is classified in the industry as an NP-hard problem in combinatorial optimization, a more succinct and understandable definition would be: given a list of destinations, what’s the best round-trip route that visits every location?

This summer brought news that the 44-year old record for solving the problem has been broken. Let’s take a look at why this is a hard problem, and how the research team from the University of Washington took a different approach to achieve the speed up.

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Arduino And Wire Detects Metal

October 21, 2020 by 7 Comments

Our old math teacher famously said, “You have to take what you know and use it find what you don’t know.” The same holds true for a lot of microcontroller designs including [rgco’s] clever metal detector that uses very little other than an Arduino. The principle of operation is simple. An Arduino can measure time, a coil and a resistor will create a delay proportional to the circuit values, and metal around the coil will change the coil’s inductance. As the inductance changes, so does the delay and, thus, the Arduino can sense metal, as you can see in the video below.

The simple principle is also simple in practice. Besides the Arduino and the coil, there’s a single resistor. You want a small coil since larger coils won’t detect smaller objects. If you don’t want to wind your own coil, [rgco] suggests using a roll of hookup wire as long as the resistance is under 10 ohms.

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Learn IC Decapping

October 21, 2020 by 15 Comments

Decapsulating ICs used to be an exotic technique. (I should know, I did that professionally for one of the big IC vendors back in the 1980s.) These days, more and more people are learning to take apart ICs for a variety of reasons. If you are interested in doing it yourself, [Juan Carlos Jimenez] has a post you should read about using acid to remove epoxy from ICs.

[Juan Carlos] used several different techniques with varying degrees of success. Keep in mind, that using nitric acid is generally pretty nasty. You need safety equipment and be sure to plan for bad things to happen. Have eyewash ready because once you splash acid in your eye, it is too late to get that together.

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Light Fields: Missing Ingredient For Immersive 3D Video Gets Improved

October 20, 2020 by 13 Comments
46 time-synchronized action cameras make up the guts of the capture device.

3D video content has a significant limitation, one that is not trivial to solve. Video captured by a camera — even one with high resolution and a very wide field of view — still records a scene as a flat plane, from a fixed point of view. The limitation this brings will be familiar to anyone who has watched a 3D video (or “360 video”) in VR and moved their head the wrong way. In these videos one is free to look around, but may not change the position of their head in the process. Put another way, pivoting one’s head to look up, down, left, or right is fine. Moving one’s head higher, lower, closer, further, or to the side? None of that works. Natural movements like trying to peek over an object, or moving slightly to the side for a better view simply do not work.

Light field video changes that. It is captured using a device like the one in the image above, and Google has a resource page giving an excellent overview of what light field video is, what it can look like, and how they are doing it. That link covers recent improvements to their camera apparatus as well as to video encoding and rendering, but serves as a great show-and-tell of what light fields are and what they can do.

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Raspberry Pi And Raspberry Pi Spy: This Is How Trademark SNAFUs Should Be Handled

October 20, 2020 by 29 Comments

In the eight years or so since the Raspberry Pi first landed as tangible hardware, we’ve all dealt with the Pi folks whether as customers or through their many online support and outreach activities. They’ve provided our community with the seed that led to an explosion of inexpensive Linux-capable single board computers, while their own offerings have powered so many of the projects we have featured here. Their heart lies in their educational remit, but they have also become an indispensable part of our community.

The statement from the Pi Foundation’s Philip Colligan.

Thus it was a surprise when [Raspberry Pi Spy], a long-time commentator on all things Pi, received a legal notice from the Raspberry Pi Foundation that their use of the Raspberry Pi name contravened the acceptable use guidelines and demanding that all content be removed and the domains be handed over. Some consternation ensued, before Pi foundation boss [Philip Colligan] released a statement retracting the original letter and explaining that the incident was the result of an over-zealous legal adviser and that the Foundation has no wish to undermine the Pi community.

All’s well that ends well, but what just happened? In the first instance, it’s natural for any organisation to wish to protect their brand, and there would be plenty of unscrupulous entities ready to sell fake Pi products were the Foundation not active in asserting their rights. In this case it seems that it was the use of the full Raspberry Pi trademark in a domain name that triggered the letter and not the fair-use blogging about the Pi products. We can see that however much we might wish otherwise it was not without legal merit. There have been numerous cybersquatting cases heard since the creation of the Web, and even though some of them have been on more dubious ground than others it remains a well-trodden path.

Where this story differs from so many others though is that the Pi Foundation acted with common sense in withdrawing the notice issued against a member of its community. It is inevitable that sometimes even the best of us can take regrettable paths by whatever means, and respect is earned by how such situations are resolved. We applaud the Pi folks for their swift action in this matter, we’d suggest to anyone that they take care when registering domain names, and we suspect that somewhere a legal adviser will be in the doghouse. But that all such incidents in our community could be resolved with such ease.

OSIRIS-REx Reaches Out And Touches Asteroid Bennu

October 20, 2020 by 7 Comments

After a four year trek through deep space, OSIRIS-REx made history this evening as it became the first NASA spacecraft to try and collect a surface sample from an asteroid (Editor’s note: servers may be down due to the breaking news). Once sensors verify the collected material is safely onboard, the vehicle will begin drifting away from the 490 meter wide Bennu in preparation of its eventual departure and return to Earth. If all goes according to plan, the craft’s conical Sample Return Capsule carrying its precious cargo will renter the atmosphere and land at the Utah Test and Training Range in September of 2023.

OSIRIS-REx with solar panels in “Y-Wing” configuration.

Due to its extremely low gravity and rocky surface, a traditional landing on Bennu was deemed impractical. Instead, OSIRIS-REx performed a daring touch and go maneuver that brought the spacecraft into contact with the surface for just a few seconds.

A camera on the bottom of the vehicle took images every few minutes during the descent and ran them through an onboard system called Natural Feature Tracking (NFT) that autonomously steered it away from dangerous surface features. As a precaution, the solar panels on the OSIRIS-REx were angled backwards in a “Y-Wing” configuration shortly before the descent to help protect them from striking the surface or being damaged by ejected material.

Once the colander-like Touch-And-Go Sample Acquisition Mechanism (TAGSAM) mounted to the end of the spacecraft’s 3.35 meter (11 foot) articulated robotic arm arm made contact with the regolith, pressurized nitrogen was used to kick up material and push it towards storage caches built into the mechanism. With so much riding on the successful collection of surface material, this largely passive system was selected to minimize the possible failures in the critical few seconds that OSIRIS-REx would be in contact with Bennu. Mission planners say it might take until Saturday to determine if a sample was successfully collected, and that the spacecraft has the ability to perform two more attempts if needed.

After its discovery in September 1999, both the Arecibo Observatory and the Goldstone Deep Space Network were used to make radar observations of Bennu to study its shape and size. Calculations have shown it has a cumulative 1 in 2,700 chance of striking the Earth by the year 2199. By mapping the asteroid, studying it at close range, and bringing a geological sample back home, NASA hopes to gain valuable insight on how similar near-Earth objects can be detected and ultimately diverted if needed.