Automated Rig Grows Big, Beautiful Crystals Fast

We haven’t seen [Les Wright] in a while, and with the release of his new video, we know why — he’s been busy growing crystals.

Now, that might seem confusing to anyone who has done the classic “Crystal Garden” trick with table salt and laundry bluing, or tried to get a bit of rock candy out of a supersaturated sugar solution. Sure, growing crystals takes time, but it’s not exactly hard work. But [Les] isn’t in the market for any old crystals. Rather, he needs super-sized, optically clear crystals of potassium dihydrogen phosphate, or KDP, which are useful as frequency doublers for lasers. [Les] has detailed his need for KDP crystals before and even grown some nice ones, but he wanted to step up his game and grow some real whoppers.

And boy, did he ever. Fair warning; the video below is long and has a lot of detail on crystal-growing theory, but it’s well worth it for anyone taking the plunge. [Les] ended up building an automated crystal lab, housing it in an old server enclosure for temperature and dust control. The crystals are grown on a custom-built armature that slowly rotates in a supersaturated solution of KDP which is carefully transitioned through a specific temperature profile under Arduino control. As a bonus, he programmed the rig to take photographs of the growing crystals at intervals; the resulting time-lapse sequences are as gorgeous as the crystals, one of which grew to 40 grams in only a week.

We’re keen to see how [Les] puts these crystals to work, and to learn exactly what a “Pockels Cell” is and why you’d want one. In the meantime, if you’re interested in how the crystals that make the whole world work are made, check out our deep dive into silicon.

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A Look Back At Google’s 2015 Chromecast

Google’s Chromecast was first released in 2013, with a more sophisticated follow-up in 2015, which saw itself joined by the Chromecast Audio dongle. The device went through an additional two hardware generations before the entire line of products was discontinued earlier this year in favor of Google TV.

Marvell's Armada 88DE3006 dual-core Cortex-A7 powers the second-generation ChromeCast. (Credit: Brian Dipert, EDN)
Marvell’s Armada 88DE3006 dual-core Cortex-A7 powers the second-generation Chromecast. (Credit: Brian Dipert, EDN)

In addition to collecting each generation of Chromecast, [Brian Dipert] over at EDN looked back on this second-generation dongle from 2015 while also digging into the guts of a well-used example that got picked up used.

While not having any of the fascinating legacy features of the 2nd-generation Ultra in his collection that came with the Stadia gaming controller, it defines basically everything that Chromecast dongles were about: a simple dongle with a HDMI & USB connector that you plugged into a display that you wanted to show streaming content on. The teardown is mostly similar to the 2015-era teardown by iFixit, who incidentally decided not to assign any repairability score, for obvious reasons.

Most interesting about this second-generation Chromecast is that the hardware supported Bluetooth, but that this wasn’t enabled until a few years later, presumably to fix the wonky new device setup procedure that would be replaced with a new procedure via the Google Home app.

While Google’s attention has moved on to newer devices, the Chromecast isn’t dead — the dongles in the wild still work, and the protocol is supported by Google TV and many ‘smart’ appliances including TVs and multimedia receivers.

British Spooks Issue Yearly Teaser

As a British taxpayer it’s reassuring to know that over in Cheltenham there’s a big round building full of people dedicated to keeping us safe. GCHQ is the nation’s electronic spying centre, and just to show what a bunch of good eggs they are they release a puzzler every year to titillate the nation’s geeks. 2024’s edition is out if you fancy trying it, so break out your proverbial thinking caps.

The puzzle comes in several stages each of which reveals a British landmark, and we’re told there’s a further set of puzzles hidden in the design of the card itself. We know that Hackaday readers possess fine minds, so you’ll all be raring to have a go.

Sadly GCHQ would for perfectly understandable reasons never let Hackaday in for a tour, but we’ve encountered some of their past work. First the Colossus replica codebreaking computer at Bletchley Park was the progenitor of the organisation, and then a few years ago when they had an exhibition from their archive in the London Science Museum.

Good Lighting On A Budget With Cordless Tool Batteries

It’s perhaps not fair, but even if you have the best idea for a compelling video, few things will make people switch off than poor lighting. Good light and plenty of it is the order of the day when it comes to video production, and luckily there are many affordable options out there. Affordable, that is, right up to the point where you need batteries for remote shoots, in which case you’d better be ready to open the purse strings.

When [Dane Kouttron] ran into the battery problem with his video lighting setup, he fought back with these cheap and clever cordless tool battery pack adapters. His lights were designed to use Sony NP-F mount batteries, which are pretty common in the photography trade but unforgivably expensive, at least for Sony-branded packs. Having access to 20 volt DeWalt battery packs, he combined an off-the-shelf battery adapter with a 3D printed mount that slips right onto the light. Luckily, the lights have a built-in DC-DC converter that accepts up to 40 volts, so connecting the battery through a protection diode was a pretty simple exercise. The battery pack just slots right in and keeps the lights running for portable shoots.

Of course, if you don’t already have DeWalt batteries on hand, it might just be cheaper to buy the Sony batteries and be done with it. Then again, there are battery adapters for pretty much every cordless tool brand out there, so you should be able to adapt the design. We’ve also seen cross-brand battery adapters which might prove useful, too.

The Disappearing Capacitor

As part of a phosphorescence detector, [lcamtuf] has been working with photodiodes. The components, like all diodes, have some capacitance at the junction, and this can limit performance. That’s why [lcamtuf] turned to bootstrapping to make that parasitic capacitance almost disappear.

The technique appears in several Analog Devices datasheets that presents a mystery. An op amp circuit that would normally limit changes to about 52 kHz has an unusually-placed JFET and claims to boost the bandwidth to 350 kHz.

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The 6GHz Band Opens In The US

On December 11th, the FCC announced that the band around 6GHz would be open to “very low-power devices.” The new allocation shares space with other devices already using these frequencies. The release mentions a few limitations over the 350 MHz band (broken into two segments). First, the devices must use a contention-based protocol and implement transmit power control. The low-power devices may not be part of a fixed outdoor infrastructure.

The frequencies are 6.425-6.525 GHz, 6.875-7.125 GHz and the requirements are similar to those imposed on 802.11ax in the nearby U-NII-5 and U-NII-7 bands.

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It’s Critical: Don’t Pile Up Your Fissionable Material

Nuclear fission is a powerful phenomenon. When the conditions are right, atomic nuclei split, releasing neutrons that then split other nuclei in an ongoing chain reaction that releases enormous amounts of energy. This is how nuclear weapons work. In a more stable and controlled fashion, it’s how our nuclear reactors work too.

However, these chain reactions can also happen accidentally—with terrifying results. Though rare, criticality incidents – events where an accidental self-sustaining nuclear chain reaction occurs – serve as sobering reminders of the immense and unwieldy forces we attempt to harness when playing with nuclear materials.

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