Hackaday Dictionary: The Global Positioning System (GPS)

November 12, 2015 by 64 Comments

One of the fundamental technologies of modern gadgets is the Global Positioning System (GPS). Using signals from satellites orbiting the earth, a GPS receiver can pin down its location with remarkable accuracy: the latest generation of Civilian Navigation Signals (CNAV) sent by the US GPS system has an accuracy of less than half a meter (about 3 feet). These signals also contain the time, accurate to within milliseconds, which makes it perfect for off-line dataloggers and systems that require very accurate timing. That’s a powerful combination that has made GPS one of the main technologies behind the mobile revolution, because it lets gadgets know where (and when) they are.

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Heat Duct Rover Explores Stink, Rescues Flashlight

November 12, 2015 by 32 Comments

It all started with a bad smell coming from the heat register. [CuddleBurrito] recalled a time when something stinky ended up in the ductwork of his folks’ house which ended up costing them big bucks to explore. The hacker mindset shies away from those expenditures and toward literally rolling your own solution to investigating the funk. In the process [CuddleBurrito] takes us on a journey into the bowels of his house.

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Black MIDI: There Is No Denser Music

November 12, 2015 by 73 Comments

Imagine if you played all the keys on a piano at once. What would it sound like? Now imagine that you’d like to transcribe that music. What would it look like? So many notes that you could hardly see the paper underneath.

Which is why the people making such “impossible music” are calling themselves the Black MIDI Crew: if you wrote the music down, it’d look like a big black blob. Or at least, that’s the joke. Amazingly, though, it doesn’t sound like a big mess. Check out “Pi, The Song With 3.1415 Million Notes” below the break to see what we mean.

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3D Printing Pen And CNC Machine Yields Cheap 3D Printer

November 11, 2015 by 22 Comments

3D printers are ubiquitous now, but they’re still prohibitively expensive for some people. Some printers cost thousands, but even more inexpensive options aren’t exactly cheap. [Daniel] decided that this was unacceptable, and set out to make a basic 3D printer for under $100 by including only the bare essentials needed for creating anything out of melted plastic.

3D printers are essentially four parts: a bed, filament, and a hot end and extruder. In a previous project, [Daniel] used parts from old CD drives to create a three-axis CNC machine which he uses for the bed. To take care of the hot end and extruder, he is using a 3D printing pen which he mounts to the CNC machine and voila: a 3D printer!

It’s not quite as simple as just strapping a 3D printing pen to a CNC machine, though. The pen and the CNC machine have to communicate with each other so that the pen knows when to place filament and the CNC machine knows when to move. For that, [Daniel] went with a trusty Arduino in order to switch the pen on and off. Once it’s working, it’s time to start printing!

[Daniel] does note that this is a design that’s relatively limited in terms of print size and resolution, but for the price it can’t be beat. If you’re interested in getting started with 3D printing, a setup like this would be perfect. 3D pens are a pretty new idea too, and it’s interesting to see them used in different ways like this.

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.