What Can A $30 USB Spectrum Analyser Do For Me?

March 8, 2021 by 36 Comments

As mildly exotic silicon has become cheaper and the ingenuity of hardware hackers has been unleashed upon it, it’s inevitable that some once-unattainably expensive instruments will appear as cheap modules from China. The LTDZ spectrum analyser on the bench today covers 35 MHz to 4.4 GHz, and has a USB interface and tracking source. It has been available from all the usual outlets for a while now either as a bare PCB or in a metal box about the size of a pack of cards.

We’ve already taken a look at the $50 VNA, and this time it’s the turn of the $30 spectrum analyser, in the form of a little device that I succumbed to while browsing Banggood.

I ordered one, along with an attenuator and RF bridge for SWR measurements, and after the usual wait for postage my anonymous grey package arrived and it was time to give it a look and consider its usefulness. It’s a design derived from one published in Germany’s Funkamateur (“amateur radio”) magazine early in the last decade, and unscrewing the end plate to slide out the board from its extruded enclosure we can see what makes it tick. Continue reading “What Can A $30 USB Spectrum Analyser Do For Me?” →

Decapping Components Hack Chat With John McMaster

March 8, 2021 by 2 Comments

Join us on Wednesday, March 10 at noon Pacific for the Decapping Components Hack Chat with John McMaster!

We treat them like black boxes, which they oftentimes are, but what lies beneath the inscrutable packages of electronic components is another world that begs exploration. But the sensitive and fragile silicon guts of these devices can be hard to get to, requiring destructive methods that, in the hands of a novice, more often than not lead to the demise of the good stuff inside.

To help us sort through the process of getting inside components, John McMaster will stop by the Hack Chat. You’ll probably recognize John’s work from Twitter and YouTube, or perhaps from his SiliconPr0n.org website, home to beauty shots of some of the chips he has decapped. John is also big in the reverse engineering community, organizing the Mountain View Reverse Engineering meetup, a group that meets regularly to discuss the secret world of components. Join us as we talk to John about some of the methods and materials used to get a look inside this world.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, March 10 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.
Continue reading “Decapping Components Hack Chat With John McMaster” →

A Scientist Made An Artificial Black Hole In The Lab, And You Won’t Believe What Happened Next

March 8, 2021 by 53 Comments

OK, that was a little click-baity, but then again, so was the announcement this week that a scientist had confirmed Hawking radiation with a lab-grown black hole. It sure got our attention, at least.

As it turns out, the truth is both less and more than meets the eye. The article above was eventually edited to better reflect the truth that, alas, we have not yet found a way to create objects so massive that even light cannot escape them. Instead, physicist [Jeff Steinhauer] and colleagues at the Technion-Israel Institute of Technology have developed an acoustic model of black holes, which is what was used to observe the equivalent of Hawking radiation for the first time. Hawking radiation is the theoretical exception to the rule that nothing makes it out of a black hole and would imply that black holes evaporate over time. The predicted radiation would be orders of magnitude weaker than the background radiation, though, making it all but impossible to detect.

That’s where [Steinhauer]’s sonic black holes come in. In these experiments, phonons, packets of mechanical vibrations that stand in for photons, are trapped in a fast-moving stream of fluid. The point in the stream where its speed straddles the local speed of sound is the equivalent to a real black hole’s event horizon; phonons inside that boundary can never escape. Except, of course, for the sonic equivalent of Hawking radiation, which the researchers found after 97,000 attempts.

When we first stumbled upon this story, we assumed a lab-grown black hole, even an acoustic analog, would take a CERN’s-worth of equipment to create. It turns out to be far simpler than that; [Steinhauer], in fact, built his black hole machine singlehandedly from relatively simple equipment. The experiments do require temperatures near absolute zero and a couple of powerful lasers, so it’s not exactly easy stuff; still, we can’t help but wonder if sonic black holes are within the reach of the DIY community. Paging [Ben Krasnow] and [Sam Zeloof], among others.

[Featured image credit: Nitzan Zohar, Office of the Spokesperson, Technion]

Sea Level: How Do We Measure Global Ocean Levels And Do Rising Oceans Change That Benchmark?

March 8, 2021 by 34 Comments

Every summer you go down the shore, but lately you’ve begun to notice that the beach seems narrower each time you visit. Is that the sea level rising, or is the sand just being swept away? Speaking of sea levels, you keep hearing that they rise higher every year — but how exactly is that measured? After all, you can’t exactly use a ruler. As it turns out, there are a number of clever systems in place that can accurately measure the global sea level down to less than an inch and a half.

Not only are waves always rippling across the ocean’s surface, but tides periodically roll in and out, making any single instantaneous measurement of sea level hopelessly inaccurate. Even if you plan to take hundreds or thousands of measurements over the course of weeks or months, taking the individual measurements is still difficult. Pick a nice, stable rock in the surf, mark a line on it, and return every hour for two weeks to hold a tape measure up to it. At best you’ll get within six inches on each reading, no matter what you’ll get wet, and at worst the rock will move and you’ll get a damp notebook full of useless numbers. So let’s take a look at how the pros do it.

Continue reading “Sea Level: How Do We Measure Global Ocean Levels And Do Rising Oceans Change That Benchmark?” →

3D Printing 90° Overhangs With Non-Planar Slicing

March 8, 2021 by 28 Comments

When slicing a model for 3D printing, the part is divided into a stack of flat, 2D layers. But there’s an alternative in the form of non-planar slicing, where the layers can follow 3D curves. [Rene K. Mueller] took this a step further and successfully used non-planar slicing to print 90° overhangs on a normal Cartesian FDM printer.

Non-planar layers have been around for a while, but were generally limited to creating smooth curves without layer lines. The idea of using the technique for overhangs had been floating around in [Rene]’s head for a while, and he was spurred to action after seeing the rotating tilted nozzle printer featured here on Hackaday. The idea is only to have the outer edge of each layer overhang, by making each layer slope downward toward the overhang. [Rene] programmed a conic slicer algorithm for this purpose, which splits the model into dome-shaped layers, like an onion.

He did a lot of testing and documented the results in detail. Conical slices were compared with tilted slices, which are also used for belt 3D printers. Both have some geometric limitations. Tilted slices can only print the overhang in one direction, but conical slices can do this in all directions, allowing it to create a mushroom-like shape without any support. The limitation is that it can only print inward or outward from a central point. More complex geometry must be segmented, and each sub-volume sliced separately. The slicing angle is also limited by the shape of the print head, to avoid it crashing into the print.

We think this technique has a lot of potential for widespread use, especially since it is compatible with most existing FDM printers. It is still a work in progress, but support has already been added for Slic3r and Prusa Slicer. We look forward to seeing how it develops and gets adopted.

AVR Configurable Custom Logic As A Frequency Divider At 4x Chip’s Clock Speed

March 8, 2021 by 13 Comments

What a time to be alive when you can find inexpensive microcontrollers that come with programmable(ish) logic that can operate independently of the system clock. [David Johnson-Davies] recently built a proof of concept using the Configurable Custom Logic (CCL) that is available in some of the newer AVR microcontroller designs. It’s a simple implementation, a set of frequency dividers that blink three LEDs with up to a 90 MHz input signal. But the simplicity is the reason to love his write-up — you can wrap your head around it right away.

There are four lookup table (LUTs) used to form the frequency divider. Think of these like a NAND or XOR gate, but you get to decide how the output truth tables will perform. The output is fed into a sequencer which can be configured as a D/JK flip-flop or a D/RS latch, plus you can specify the signal edge, and of course define the clock source. An interesting trick here is to hold the G input of both D flip-flops high by feeding them LUTs set to all ones. Note that the output of the first divider (PA3) is feeding the external input (PD2) of the second divider.

While the CCL is configured using the C code you flash to the microcontroller, it’s a hardware peripheral capable of operating independent of the chip’s system clock. The AVR128DA28 that’s used here tops out at 24 MHz (double that if you use the PLL) but [David] got reliable results from his clock divider feeding a signal as high as 90 MHz to the input pin. Of course you have the option of feeding internal clock signals to the CCL, but that wouldn’t seem nearly as interesting here. For the demo, [David] is actually toggling an IO pin which is connected to PA2 as the external input for the logic. Make sure you click through to his write-up linked above as he does an excellent job of walking through the sample code (just a couple-dozen lines to set this all up). Here’s the datasheet for this chip (PDF, page 447 for pertinent registers) and for a deeper dive the appnote on CCL (PDF).

So what is this all good for? We already saw an answer to that question back in January when [SM6VFZ] used the CCL peripheral to build a software-defined switch-mode converter. How awesome is that?

A Tiny Tube Amp For Not A Lot

March 7, 2021 by 49 Comments

At the extreme budget end of tube audio lie single-tube amplifiers usually using very cheap small-signal pentodes. They’ve appeared here before in various guises, and a fitting addition to those previous projects comes from [Kris Slyka]. It’s a classic circuit with a transformer output, and it provides enough amplification to drive a pair of headphones or even a speaker at low levels.

The fairly conventional circuit of the tube amplifier.

Most tube enthusiasts will instantly recognize the anode follower circuit with a transformer in the anode feed through which the output is taken. The tube works in Class A, which means that it’s in its least efficient mode but the one with the least distortion. The transformer itself isn’t an audio part, but a small mains transformer taken from a scrap wall wart. It serves not only for isolation, but also to transform the high impedance output from the tube into a low impedance suitable for driving a headphone or speaker.

The HT voltage is a relatively low 24 V, but it still manages to drive headphones acceptably. Speaker levels require a pre-amp, but even then it’s likely that this circuit is pushing the tube beyond what it’s capable of with a speaker. The more it operates towards the edge of its performance envelope the more distortion it will generate and the worse a sound it will produce. This isn’t such a problem in a guitar application as here, but hi-fi enthusiasts may find it to be too much. It would be interesting to subject it as a headphone amplifier to a series of audio tests to evaluate the effect of a mains transformer over a dedicated audio one.

Last year we took a very in-depth look at the commonly-available Chinese kit pre-amps that use a similar anode-follower circuit but without the transformer. We’ve also seen a similar amp that uses an op-amp as an impedance converter, as well as a novel take on the idea whose unusual biasing allows it to run from only 3.3 volts. These circuits can be so cheap to get started with that we’d suggest anyone give them a try.