DSP Spreadsheet: IQ Diagrams

November 15, 2019 by Al Williams 5 Comments

In previous installments of DSP Spreadsheet, we’ve looked at generating signals, mixing them, and filtering them. If you start trying to work with DSP, though, you’ll find a topic that always rears its head: IQ signals. It turns out, these aren’t as hard as they appear at first and, as usual, we’ll tackle them in a spreadsheet.

What does IQ stand for? The I stands for “in phase” and the Q stands for quadrature. By convention, the I signal is a cosine wave and the Q signal is a sine wave. Another way to say that is that the I and Q signals are 90 degrees out of phase. By manipulating the amplitude of I and Q, you can create complex modulation or, conversely, demodulate signals. We’ll see a spreadsheet that shows that completely next time.

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Jubilee: A Toolchanging Homage To 3D Printer Hackers Everywhere

November 14, 2019 by Sonya Vasquez 36 Comments

I admit that I’m late to the 3D printing game. While I just picked up my first printer in 2018, the rest of us have been oozing out beautiful prints for over a decade. And in that time we’ve seen many people reimagine the hardware for mischief besides just printing plastic. That decade of hacks got me thinking: what if the killer-app of 3D printing isn’t the printing? What if it’s programmable motion? With that, I wondered: what if we had a machine that just offered us motion capabilities? What if extending those motion capabilities was a first class feature? What if we had a machine that was meant to be hacked?

One year later, I am thrilled to release an open-source multitool motion platform I call Jubilee. For a world that’s hungry for toolchanging 3D printers, Jubilee might be the best toolchanging 3D printer you can build yourself–with nothing more than a set of hand tools and some patience. But it doesn’t stop there. With a standardized tool pattern established by E3D and a kinematically coupled hot-swappable bed, Jubilee is rigged to be extended by anyone looking to harness its programmable motion capabilities for some ad hoc automation.

Jubilee is my homage to you, the 3D printer hacker; but it’s meant to serve the open-source community at large. Around the world, scientists, artists, and hackers alike use the precision of automated machines for their own personal exploration and expression. But the tools we use now are either expensive or cumbersome–often coupled with a hefty learning curve but no up-front promise that they’ll meet our needs. To that end, Jubilee is meant to shortcut the knowledge needed to get things moving, literally. Jubilee wants to be an API for motion.

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Ask Hackaday: Is Anyone Sad Phone VR Is Dead?

November 13, 2019 by Donald Papp 92 Comments

It’s official: smartphone-based VR is dead. The two big players in this space were Samsung Gear VR (powered by Oculus, which is owned by Facebook) and Google Daydream. Both have called it quits, with Google omitting support from their newer phones and Oculus confirming that the Gear VR has reached the end of its road. Things aren’t entirely shut down quite yet, but when it does it will sure leave a lot of empty headsets laying around. These things exist in the millions, but did anyone really use phone-based VR? Are any of you sad to see it go?

Google Cardboard, lowering cost and barrier to entry about as low as it could go.

In case you’re unfamiliar with phone-based VR, this is how it works: the user drops their smartphone into a headset, puts it on their head, and optionally uses a wireless controller to interact with things. The smartphone takes care of tracking motion and displaying 3D content while the headset itself takes care of the optics and holds everything in front of the user’s eyeballs. On the low end was Google Cardboard and on the higher end was Daydream and Gear VR. It works, and is both cheap and portable, so what happened?

In short, phone-based VR had constraints that limited just how far it could go when it came to delivering a VR experience, and these constraints kept it from being viable in the long run. Here are some of the reasons smartphone-based VR hit the end of the road: Continue reading “Ask Hackaday: Is Anyone Sad Phone VR Is Dead?” →

pierced puffed exposed leads lithium ion battery

Lessons In Li-Ion Safety

November 13, 2019 by Bob Baddeley 85 Comments

If you came here from an internet search because your battery just blew up and you don’t know how to put out the fire, then use a regular fire extinguisher if it’s plugged in to an outlet, or a fire extinguisher or water if it is not plugged in. Get out if there is a lot of smoke. For everyone else, keep reading.

I recently developed a product that used three 18650 cells. This battery pack had its own overvoltage, undervoltage, and overcurrent protection circuitry. On top of that my design incorporated a PTC fuse, and on top of that I had a current sensing circuit monitored by the microcontroller that controlled the board. When it comes to Li-Ion batteries, you don’t want to mess around. They pack a lot of energy, and if something goes wrong, they can experience thermal runaway, which is another word for blowing up and spreading fire and toxic gasses all over. So how do you take care of them, and what do you do when things go poorly?

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HF Propagation And Earthquakes

November 12, 2019 by Dan Maloney 25 Comments

For all the successes of modern weather forecasting, where hurricanes, blizzards, and even notoriously unpredictable tornadoes are routinely detected before they strike, reliably predicting one aspect of nature’s fury has eluded us: earthquakes. The development of plate tectonic theory in the middle of the 20th century and the construction of a worldwide network of seismic sensors gave geologists the tools to understand how earthquakes happened, and even provided the tantalizing possibility of an accurate predictor of a coming quake. Such efforts had only limited success, though, and enough false alarms that most efforts to predict earthquakes were abandoned by the late 1990s or so.

It may turn out that scientists were looking in the wrong place for a reliable predictor of coming earthquakes. Some geologists and geophysicists have become convinced that instead of watching the twitches and spasms of the earth, the state of the skies above might be more fruitful. And they’re using the propagation of radio waves from both space and the ground to prove their point that the ionosphere does some interesting things before and after an earthquake strikes.

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RISC-V: Why The ISA Battles Aren’t Over Yet

November 12, 2019 by Maya Posch 39 Comments

A computer processor uses a so-called Instruction Set Architecture to talk with the world outside of its own circuitry. This ISA consists of a number of instructions, which essentially define the functionality of that processor, which explains why so many ISAs still exist today. It’s hard to find that one ISA that works for as many distinct use cases as possible, after all.

A fairly new ISA is RISC-V, the first version of which was created back in 2010 at the University of California, Berkeley. Intended to be a fully open ISA, targeting both students (as a learning tool) and industrial users, it is claimed to incorporate a number of design choices that should make it more attractive for a number of applications.

In this article I’ll take a look behind the marketing to take stock of how exactly RISC-V differs from other open ISAs, including Power, SPARC and MIPS.

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Network Booting The Pi 4

November 11, 2019 by Jonathan Bennett 106 Comments

We’ve talked about PXE booting the Raspberry Pi 3B+, and then looked at the Raspberry Pi 4 as a desktop replacement. But there’s more! The Pi 4 sports a very useful new feature, the flashable bootloader. Just recently a beta version of that bootloader was released that supports PXE — booting up over the network — which has become a must-have for those of us who have had consistently bad experiences with root filesystems on SD cards.

What are the downsides, I hear you ask? You might see slower speeds going across the network compared to a high quality SD card, particularly with the Pi 4 and its improved SD card slot. PXE does require an Ethernet cable; WiFi is not enough, so you have that restriction to contend with. And finally, this isn’t a portable option — you are tethered to that network cable while running, and tethered to your network to boot at all.

On the other hand, if you’re doing a permanent or semi-permanent install of a Pi, PXE is absolutely a winner. There are few things worse than dragging a ladder out to access a Pi that’s cooked its SD card, not to mention the possibility that you firewalled yourself out of it. Need to start over with a fresh Raspbian image? Easy, just rebuild it on the PXE server and reboot the Pi remotely.

Convinced PXE is for you? Let’s get started! Continue reading “Network Booting The Pi 4” →