The laser driver's internals, showing the custom PCB, the PSU, connectors and the interlocks.

Laser Driver Design Keeps Safety First

May 29, 2022 by Arya Voronova 20 Comments

[Les] from [Les’ Lab] has designed a driver for laser diodes up to 10 watts, and decided to show us how it operates, tells us what we should keep in mind when designing such a driver, and talks about laser safety in general. This design is an adjustable current regulator based on the LM350A, able to provide up to 10 watts of power at about 2 volts – which is what his diode needs. Such obscure requirements aren’t easily fulfilled by commonly available PSUs, which is why a custom design was called for.

He tells us how he approached improving stability of the current regulation circuit, the PCB design requirements, and planning user interface for such a driver. However, that’s just part of the battle – regulating the current properly is important, but reducing the potential for accidental injuries even more so. Thus, he talks extensively about designing the driver circuit with safety in mind – using various kinds of interlocks, like a latching relay circuit to prevent it from powering up as soon as power is applied.

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Upcycled Practice Amp Build Goes To Eleven

May 26, 2022 by Dan Maloney 19 Comments

What do you call someone who gives the toddler in your life a musical instrument as a gift? In most cases, “mortal enemy” is the correct answer, but not everyone feels quite so curmudgeonly, and might even attempt to turn up the volume a bit. Such is the case with this wonderfully detailed practice amp for the grandkids’ electric ukelele.

~~The aptly named [packrat]~~ [Professor Mayhem] really made this build a tour de force of scrap bin sourcing. The amp is built around a module salvaged from an old TV, a stereo Class-D amp that was modified to provide 30 watts output and a volume control. The driver came from a flood-damaged speaker unit, and the power supply from a gutted wall wart. The case was built with scrap plywood and covered with pebble-grain fabric to give it that pro audio look, while the chassis for the electronics was bent from a piece of sheet steel.

But it’s the tiny details that really sell this project. Everything from the pilot light to the pointer knob screams 1970s, as do the painstaking front panel lettering and vinyl “Monkeydyne” logo. [Professor Mayhem] even went the extra mile to create an etched-brass serial number plate, a mock specs and safety label, and even a QA inspection tag that was (sort of) stapled inside the cabinet.

We tip our hats to [Professor Mayhem] for this four-month labor of love and obvious nostalgia trip, which the kids are sure to love. [Professor Mayhem] does admit that some will argue with his decision to use a Class D amp and a switch-mode power supply, but let’s be real — for the application, it’s probably more than sufficient.

Thanks for the tip, [packrat].

Hackaday Podcast 168: Math Flattens Spheres, FPGAs Emulate Arcades, And We Can’t Shake Polaroid Pictures

May 13, 2022 by Dan Maloney 5 Comments

Join Hackaday Editor-in-Chief Elliot Williams and Staff Writer Dan Maloney as they review the top hacks for the week. It was a real retro-fest this time, with a C64 built from (mostly) new parts, an Altoids Altair, and learning FPGAs via classic video games. We also looked at LCD sniffing to capture data from old devices, reimagined the resistor color code, revisited the magic of Polaroid instant cameras, and took a trip down television’s memory lane. But it wasn’t all old stuff — there’s flat-packing a sphere with math, spraying a fine finish on 3D printed parts, a DRM-free label printer, and a look at what’s inside that smartphone in your pocket — including some really weird optics.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments below!

Direct Download link.

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Vintage Computer Festival East Raises The Bar Again

May 2, 2022 by Tom Nardi 34 Comments

When I arrived at the InfoAge Science and History Museum for this year’s Vintage Computer Festival East, I fully expected it to be a reduced event compared to last year. After all, how could it not? Due to the schedule getting shifted around by COVID, show runner Jeffrey Brace and his team had just six months to put together an event that usually gets planned over the course of an entire year. With such a truncated preparation time, they more than deserved a little slack.

But as anyone who attended VCF East 2022 can attest, they didn’t need it. Not only did the event meet the high expectations set by last year’s Festival, it managed to exceed them. There were more workshops, more talks, more vendors, more consignment rooms, more live streams, more…well, everything. This year’s program even got a splash of glossy color compared to the grayscale handout attendees received in October. It was, by any metric you care to use, better than ever.

It does however leave me in somewhat on an unenviable position. As we’ve learned during the pandemic, a virtual representation of an event as extensive as VCF can give you a taste of what’s offered, but all the nuance is lost. Looking at pictures of somebody’s passion project can’t compare to actually meeting the person and seeing that glint of pride in their eye as they walk you through all the details.

So bear that in mind through this rundown of some of the projects that caught my eye. This isn’t a “best of” list, and the Festival is certainly not a competition. But each attendee will invariably come away with their own handful of favorite memories, so I’ll document mine here. If you’d like to make your own memories, I’d strongly suggest making the trek out to the Jersey Shore come April 2023 for the next Vintage Computer Festival East.

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Multiband Crystal Radio Set Pulls Out All The Stops

April 28, 2022 by Dan Maloney 23 Comments

Most crystal radio receivers have a decidedly “field expedient” look to them. Fashioned as they often are from a few turns of wire around an oatmeal container and a safety pin scratching the surface of a razor blade, the whole assembly often does a great impersonation of a pile of trash whose appearance gives little hope of actually working. And yet work they do, usually, pulling radio signals out of thin air as if by magic.

Not all crystal sets take this slapdash approach, of course, and some, like this homebrew multiband crystal receiver, aim for a feature set and fit and finish that goes way beyond the norm. The “Husky” crystal set, as it’s called by its creator [alvenh], looks like it fell through a time warp right from the 1920s. The electronics are based on the Australian “Mystery Set” circuit, with modifications to make the receiver tunable over multiple bands. Rather than the traditional galena crystal and cat’s whisker detector, a pair of1N34A germanium diodes are used as rectifiers — one for demodulating the audio signal, and the other to drive a microammeter to indicate signal strength. A cat’s whisker is included for looks, though, mounted to the black acrylic front panel along with nice chunky knobs and homebrew rotary switches for band selection and antenna.

As nice as the details on the electronics are, it’s the case that really sells this build. Using quarter-sawn oak salvaged from old floorboards. The joinery is beautiful and the hardware is period correct; we especially appreciate the work that went into transforming a common flat washer into a nickel-plated escutcheon for the lock — because every radio needs a lock.

Congratulations to [Alvenh] for pulling off such a wonderful build, and really celebrating the craftsmanship of the early days of radio. Need some crystal radio theory before tackling your build? Check out [Greg Charvat]’s crystal radio deep dive.

Upcycled Nixie Clock Fit For A Friend

April 7, 2022 by Chris Wilkinson No comments

Building a clock from parts is a rite of passage for makers, and often represents a sensible introduction into the world of electronics. It’s also hard to beat the warm glow of Nixie tubes in a desktop clock, as [Joshua Coleman] discovered when building a Nixie tube clock for a friend.

The original decision to upcycle the chassis from an unrepairable Heathkit function generator came a little undone after some misaligned cutting, so the front panel ended up being redesigned and 3D printed. This ended up being serendipitous, as the redesigned front panel allowed the Nixie tubes to be inset within the metal chassis. This effect looks great, and it also better protects the tubes from impact damage.

Sourcing clones of the 74141 Nixie driver ICs ended up being easier than anticipated, and the rest of the electronics came together quickly. The decoders are driven by an Arduino, and the IN-4 Nixie tubes are powered by a bespoke 170 volt DC power supply.

Unfortunately four of the tubes were damaged during installation, however replacements were readily available online. The gorgeous IN-4 Nixie tube has a reputation for breaking easily, but is priced accordingly on auction sites and relatively easy to source.

The build video after the break should get any aspiring Nixie clock makers started, but the video description is also full of extra information and links for those needing help getting started.

We’re not short on clock hacks here at Hackaday, so why not check out a couple more? This retro-inspired LED clock looks like its right out of a parallel universe, or maybe this stunning Nixie clock driven by relays will strike your fancy.

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High Tech Pancake Tesla Coil Brings The Lightning

March 18, 2022 by Tom Nardi 4 Comments

For several years now we’ve been following [Jay Bowles] as he brings high-voltage down to Earth on his Plasma Channel YouTube channel. From spark gaps made of bits of copper pipe to automotive ignition coils driven by the stalwart 555 timer, he’s got a real knack for keeping his builds affordable and approachable. But once in a while you’ve got to step out of your comfort zone, and although the dedicated DIY’er could still replicate the solid state “pancake” Tesla coil he documents in his latest video, we’d say this one is better left for the professionals.

The story starts about nine months ago, when [Jay] was approached by fellow YouTuber [LabCoatz] to collaborate on a PCB design for a solid state Tesla coil (SSTC). Rather than a traditional spark gap, a SSTC uses insulated-gate bipolar transistors (IGBTs) triggered by an oscillator, which is not only more efficient but allows for fine control of the primary coil. The idea was to develop an AC-powered coil that was compact, easy to repair, and could be controlled with just a couple dials on the front panel. The device would also make use of an antenna feedback system that would pick up the resonant frequency of the secondary coil and automatically adjust the IGBT drive to match.

Being considerably more complex than many of the previous builds featured on Plasma Channel, it took some time to work out all the kinks. In fact, the majority of the video is [Jay] walking the viewer through the various failure modes that he ran into while developing the SSTC. Even for somebody with his experience in high-voltage, there were a number of headscratchers that had to be solved.

For example, the first version of the design used metal bolts to attach the primary and secondary coils, until he realized that was leading to capacitive coupling and replaced them with acrylic blocks instead. If his previous videos surprised you by showing how easy it could be to experiment with high-voltages, this one is a reminder that it’s not always so simple.

But in the end [Jay] does get everything sorted out, and the results are nothing short of spectacular. Even on the lower power levels it throws some impressive sparks, but when cranked up to max, it offers some of the most impressive visuals we’ve seen so far from Plasma Channel. It was a lot of work, but it certainly wasn’t wasted effort.

Fascinated by the results, but not quite ready to jump into the deep end? This affordable and easy to build high-voltage generator featured on Plasma Channel back in 2020 is a great way to get started. If you still need more inspiration, check out the fantastic presentation [Jay] gave during the 2021 Remoticon.

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