Improving WiFi Throughput With FM Radio

November 11, 2015 by 16 Comments

WiFi networking is one of those things that is reasonably simple to use, but has a lot of complex hidden features (dare we say, hacks) that make it work, or work better. For example, consider the Distributed Coordination Function (DCF) specified in the standard. Before a station can send, it has to listen for a certain time period. If the channel is clear, the station sends. If not, it has to delay a random amount of time before trying again. This is a form of Carrier Sense Multiple Access (CSMA) channel management.

Unfortunately, listening time is dead time when–at least potentially–there is no data transmitted on the network. DCF allows you to use various handshaking packets to do virtual carrier detection and ready/clear to send, but these are also less efficient use of bandwidth. There are other optional coordination functions available in the WiFi standard, but they all have their drawbacks.

[Aleksandar Kuzmanovic] at Northwestern University and two of his students have recently published a paper with a new way to coordinate multiple unrelated wireless networks using ubiquitous FM broadcast radio signals called WiFM. Instead of trying to synchronize to the WiFi data channel, this new scheme selects a strong FM radio station that broadcasts Radio Data Service (RDS) data (the data that populates the song titles and other information on modern radios).

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Are Your 3D Prints Toxic?

November 11, 2015 by 78 Comments

With the rising popularity and increasing availability of 3D printers, it was inevitable that someone would start looking into the potential environmental impact presented by them. And now we have two researchers from the University of California Riverside sounding the alarm that certain plastics are toxic to zebrafish embryos (abstract only; full paper behind a paywall).

As is often the case with science, this discovery was serendipitous. Graduate student [Shirin Mesbah Oskui] was using 3D printed tools to study zebrafish embryos, a widely used model organism in developmental biology, but she found the tools were killing her critters. She investigated further and found that prints from both a Stratasys Dimension Elite FDM printer and from a Formlabs Form 1+ stereolithography printer were “measurably toxic” to developing zebrafish embryos. The resin-based SLA printed parts were far worse for the fish than the fused ABS prints – 100% of embryos exposed to the Form 1+ prints were dead within seven days, and the few that survived that long showed developmental abnormalities before they died. Interestingly, the paper also describes a UV-curing process that reduces the toxicity of the SLA prints, which the university is patenting.

Of course what’s toxic to zebrafish is not necessarily a problem for school kids, as the video below seems to intimate. Still, this is an interesting paper that points to an area that clearly needs more investigation.

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Frank Makes A CNC Table

November 11, 2015 by 13 Comments

[Frank Howarth] is one of the big guns when it comes to woodworking on YouTube, and now he’s doing something completely unlike his other builds. He’s building a gigantic CNC machine. Yes, we’ve seen dozens of CNC router builds, but this one adds a few nifty features we’ve never seen before.

The plans for [Frank]’s CNC machine call for a 4 foot by 8 foot table, over which a router on a gantry gnaws away at wood. This is the standard size for shop-sized CNC router, but [Frank] is adding in his own twist: he’s building a 12 foot long table, by way of a four foot extension. This one small addition allows [Frank] to put tenons in tree trunks, engravings on the side of furniture, or just to make one part of a very large piece flat.

Right now, the build is just about the base, constructed out of 2″ square steel tube. While the welding is by all accounts an amateur job, everything is square, straight, and true. Now, with a metal base scooting around on hockey puck feet, [Frank] is ready to start on the robotic part of the build, something we’re all interested to see.

It’s going to be really big, but still not the biggest.

Getting Started With GNU Radio

November 11, 2015 by 25 Comments

Software Defined Radio (SDR)–the ability to process radio signals using software instead of electronics–is undeniably fascinating. However, there is a big gap from being able to use off-the-shelf SDR software and writing your own. After all, SDRs require lots of digital signal processing (DSP) at high speeds.

Not many people could build a modern PC from scratch, but nearly anyone can get a motherboard, some I/O cards, a power supply, and a case and put together a custom system. That’s the idea behind GNU Radio and SDR. GNU Radio provides a wealth of Python functions that you can use to create sophisticated SDR application (or, indeed, any DSP application).

If Python is still not up your alley (or even if it is), there’s an even easier way to use GNU Radio: The GNU Radio Companion (GRC). This is a mostly graphical approach, allowing you to thread together modules graphically and build simple GUIs to control you new radio.

Even though you usually think of GRC as being about radios, it is actually a good framework for building any kind of DSP application, and that’s what I’ll show you in the video below. GRC has a signal generator block and interfaces to your sound card. It even has the ability to read and write data to the file system, so you can use it to do many DSP applications or simulations with no additional hardware.

UPDATE: Don’t miss the follow-up post that uses SDRPlay to build a GNU Radio based receiver.

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The Running Cat

November 11, 2015 by 58 Comments

Cats are great to have around, but they need exercise. If you’re not in a position to let the cat outdoors, you need to look to something else when kitty wakes up bored from her 23 hour nap. Cat playscapes are useful diversions, but this is the first time we’ve considered real exercise equipment. Let’s get our feline friends their exercise fix with a hamster-esque cat exercise wheel.

[bbarlowski]’s design is simple but very clever, and almost looks like something you’d find flat-packed at IKEA. Built of CNC-milled birch plywood, the wheel rims snap together like puzzle pieces while the floor has tabs that slot into the rims. The tension of the bent floor panels locks everything together and makes for a smart looking wheel. The video after the break shows [Kuna the Maine Coon cat] in action on the wheel, and outlines a few plans for expansion, including adding an Arduino to monitor kitty’s activity and control both an RGB LED strip for mood lighting and a cat treat dispenser for positive reinforcement of the exercise regimen.

The project mounted an unsuccessful campaign in March and they’ve made the DXF cutting files available for download. Of course if it’s too much plywood and not enough Arduino for you, just build the Arduspider to torture – err, entertain your cat.

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What Do Bertlmann’s Socks Mean To The Nature Of Reality?

November 11, 2015 by 41 Comments

One can be reasonably certain that when the title of an article includes the phrase “The Nature of Reality”, thought provoking words must surely lie ahead.  But when that same title seems to inquire about a gentleman’s socks,  coupled with an image of said gentleman’s socks which happen to be mismatched and reflect very loud colors , one might be moved in a direction which suggests the article is not of a serious nature. Perhaps even some sort of parody.

It is my hope that you will be pleasantly surprised with the subtle genius of Irish physicist [John Bell] and his use of socks, washing machines, and a little math to show how we can test one of quantum physic’s most fundamental properties. A property that does indeed reside in the very nature of the reality we are a part of. Few people can say they understand the Bell Inequality down to its most fundamental level. Give me a little of your time, and you will be counted among these few.

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Video With Sensor Data Overlay Via Arduino Mega

November 11, 2015 by 17 Comments

If you haven’t been paying attention, big wheel trikes are a thing. There are motor driven versions as well as OG pedal pushing types . [Flux Axiom] is of the OG (you only get one link, now its on you) flavor and has written an instructable that shows how to achieve some nice looking on screen data that he syncs up with the video for a professional looking finished product which you can see in the video after the break.

[Flux Axiom] is using an Arduino Mega in his setup along with a cornucopia of sensors and all their data is being logged onto an SD card. All the code used in his setup is available in his GitHub repository. [Flux Axiom] was also nice enough to include the calibration process he used for the sensors which is also located in the GitHub download.

Sadly [Flux Axiom] uses freedom hating software for combining the video and data, Race Render 3 is his current solution and he is pleased with the results. Leave it in the comments if you have an open source solution for combining the video and data that we can offer him as a replacement.

Edit: Correct spelling of handle.

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