3D Printing Custom LED Bar Graphs

[BikerGlen] wanted to spice up his zombie containment unit (see video below) so he designed and 3D printed some very cool looking bar graphs. Apparently, you can get curved bar graph LEDs, but only if you buy a fairly large quantity. Hand soldering discrete LEDs at the perfect angle would be frustrating, but with a 3D printed jig, it was a piece of cake.

The devices use a MAX6954 LED driver, so it needs very few parts and takes commands via SPI. The chips were not cheap, but the small size and high integration sold [Glen] on it.

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The Curse Of The 40673: Zombie Components That Refuse To Die

As a fresh-faced electronic engineering student while the first Gulf War was raging in a far-off desert, I learned my way through the different families of 74 logic at a university in the North of England. 74LS was the one to use, the story went, because it’s quick and doesn’t use much power. At the time, there was an upstart on the scene: 74HC. Now that’s really quick. New. Exotic, even.

Thus an association was formed, when you want a quick logic function then 74HC is the modern one to go for. It could have been a lifelong love affair, but over twenty years, after many factors of speed increases and some RF tricks with gates we wouldn’t have dreamed of back then, it’s over. There is a whole world of newer logic families to choose from, and while HC is still good at what it does, it’s well past time to admit that it may just have been superseded.

40673s, probably now worth more by weight than anything else on four legs.
40673s, probably now worth more by weight than anything else on four legs. (Thanks are due to [Brandon Dunson] and Tanner Electronics)
 A tendency to cling to the past with logic families is pretty harmless. Like [Adam Fabio]’s TIP power transistors they’re pretty cheap, still very much in production, and still do most jobs demanded of them excellently. But what prompted this piece was a far more egregious example of an old component still being specified: the RCA 40673 dual-gate MOSFET. Launched in the mists of time when dinosaurs probably still roamed the earth, this static-sensitive four-pin TO72 found a home in a huge variety of RF amplifiers, oscillators, and mixers. It worked well, but as you might expect better devices came along, and the 40673 was withdrawn some time in the 1980s.

Unfortunately, nobody seems to have told a section of the amateur radio community about the 40673’s demise. Or perhaps nobody’s told them that many scrap analogue TV tuners of a certain age will yield a perfectly good newer replacement for free. Because even today, thirty years after the 40673 shuffled off this mortal coil, you can still find people specifying it. If you have a stash of them in your junk box, they’re worth a small fortune, and yours could be the bench with the throng of people at the next ham radio convention.

A different but equally annoying manifestation of the phenomenon comes when the device everyone likes to specify is not very old and very much still in production, but the designer hasn’t taken the time required to check for a cheaper alternative. Nobody ever got fired for buying IBM, they say, but perhaps they should be fired for specifying an AD8307 logarithmic amplifier in an amateur radio power meter. Don’t take this the wrong way, it’s a beautiful chip and probably a lot of work at Analog Devices has gone into laser-trimming resistors to make it perform to an extremely demanding specification. But eleven dollars for a chip? When a cursory search will turn up Maxim’s MAX9933 which does a perfectly good job in this application at well under two dollars? Someone isn’t doing their homework.

Sometimes there are components for which there are no perfect replacements. Germanium point-contact diodes, for example. 1N34As and OA91s are becoming like hen’s teeth these days, and though Schottky diodes can replace them in many applications, there are still a few places if you’re a radio person you’ll hanker for the original.  There are suppliers on Alibaba who claim to manufacture 1N34s, but the pictures always look suspiciously like 1N4148s, and anyway who can find a home for a hundred thousand diodes? (Hang on, this is Hackaday. There will be someone out there with a hundred-thousand-diode project, you can count on it.)

OK, maybe germanium diodes are an edge case and the examples above have a radio flavour, but you get the picture. What the full-blown rant in the previous paragraphs has been building up to is this: a plea for designers to do their homework. Please try to design every project for the next two decades, and as though any extras in the component price come from your company’s bottom line. (We’ll make exceptions for building something for which the whole point is a retro circuit. An Apple I replica like the Mimeo 1 needs old logic chips for artistic purposes.)

Is there a vital electronic engineering skill that’s being lost here perhaps? Back when the Internet was the sole preserve of boffins and Tim Berners-Lee hadn’t yet plugged his hypertext ideas into it, we relied on catalogs. Big paper-bound books the size of telephone directories were our only window into the exciting world of electronic components. If you’re an American yours was probably from Radio Shack, but for most UK-based hackers and makers who couldn’t get their hands on a commercial account from RS or Farnell that meant the Maplin catalogue. Before they moved in a consumer-electronics direction, they were a component specialist whose catalogue with its distinctive spaceships on the cover could be bought at large newsstands.

It’s difficult to describe the impact of electronics catalogues in the ’70s and ’80s to someone who has known only the abundance of information from the WWW. These publications were our only window into the world of electronic components. They contained significant excerpts from semiconductor data sheets, and we read their wealth of information from cover to cover. We knew by heart what each device was capable of, and we eagerly devoured each new tidbit of information as it arrived.

In short, when we specified a component, we did so with a pretty good knowledge of all the components that were available to us.

By comparison, nowadays we can quickly buy almost any device or component in production from a multitude of suppliers. There are millions more devices available, and if RS or Farnell don’t have the part then Mouser or Digi-Key are sure to provide. The WWW allows us to find what we need in short order, and the miracle of global distribution means that we can have it delivered within 48 hours almost wherever we live.

CPC's very aptly-named Big Book
CPC’s very aptly-named Big Book

Which means that all the new devices are available to us, but we’ve lost the ability to keep on top of them. We’ve become information rich, but knowledge poor. Printed catalogs still exist, but the sheer volume of information they contain forces brevity upon their entries and expands the size of the publication to the point at which it becomes an unwieldy work of reference. We therefore tend to stick with the devices and components we know, regardless of their cost or of whether they have been superseded, and our work is poorer for it.

We need to relearn the skill of inquisitiveness when it comes to the parts we use, and to rediscover the joy of just browsing, even if the medium is now a huge suppliers’ web site rather than a paper catalog. Otherwise we’ll still be looking at circuit diagrams containing 74LS logic and 40673 MOSFETs in the 2030s, and that can’t be a good thing!

There is of course also a slightly macabre alternative scenario. The highest online price we found for 40673s was over $30 each, so if a producer can make that kind of silly money then there’s a danger that RCA’s successors will see a business model in exhuming the corpse and re-animating it, thus ensuring that we’ll never be free of the undead. We need to make sure that doesn’t happen!

Zombie image credit: By Fabien Rougié (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Becoming A Zombie with the Hackable Electronic Badge

Last week, Parallax released an open hackable electronic badge that will eventually be used at dozens of conferences. It’s a great idea that allows badge hacks developed during one conference to be used at a later conference.

[Mark] was at the Hackable Electronics Badge premier at the 2015 Open Hardware Summit last weekend, and he just finished up the first interactive hack for this badge. It’s the zombie apocalypse in badge form, pitting humans and zombies against each other at your next con.

The zombie survival game works with the IR transmitter and receiver on the badge normally used to exchange contact information. Upon receiving the badge, the user chooses to be either a zombie or survivor. Pressing the resistive buttons attacks, heals, or infects others over IR. The game is your standard zombie apocalypse affair: zombies infect survivors, survivors attack zombies and heal the infected, and the infected turn into zombies.

Yes, a zombie apocalypse is a simple game for a wearable with IR communications, but for the Hackable Electronics Badge, it’s a great development. There will eventually be tens of thousands of these badges floating around at cons, and having this game available on day-one of a conference will make for a lot of fun.

The Best Project We Never Did Yet

Back when [Caleb] was around here at Hackaday, he was tasked with making a few YouTube videos. His Portal Gun got 1.6 Million views, and we got a takedown request because of this video even though that company was more than willing to use [Caleb] as a guinea pig at CES.

This post is not about those videos. This post is about the best project we never did yet.

The grand plan for The Best Project was a zombie survival van. It’s exactly what you think it is: a van armored and armed for driving through a herd of walkers. Proposed mods included a cow catcher and roof rack, a motorized turret, a poofer (propane tanks shooting fire from underneath the van), a bartender that launches molotov cocktails, and a beautiful little contraption called an ankler. The Ankler is just a pair of chainsaws that fold out from under the van.

The base vehicle would be a 60s VW bus. [Caleb]’s a big fan of aircooled stuff, and if you think about it, 60s VWs are pretty good for the zombie apocalypse. If you’re doubting that, just ask how many tools it would take to change out the engine in your car.

Although the dream of a Hackaday aircooled zombie apocalypse van died when [Caleb] left, that doesn’t mean we’re still not considering an official Hackaday ride. All of this is still in the planning stages, but we have a few ideas; the first, and biggest, is a mobile hackerspace on a trailer. This would be a standard semitrailer, loaded up with tools, 3D printers, a laser cutters, and a couch. It would be the perfect thing to load up with swag and haul to events.

We’re considering another more sensible vehicle, and right now the top contender is an early 2000s Astro or Safari cargo van. Yes, I know what you’re thinking: the coolest vehicle we could come up with is a minivan. There’s actually some logic to this, so hear me out.

The Astro/Safari shares a lot of parts with the S10, and that means parts are everywhere. The Astro has an AWD variant, and with a 4″ lift, upgraded suspension and big, knobby tires the Hackaday van would be very, very fun to take out into the desert. It can haul eight foot sheets of plywood, they’re cheap, everywhere, and they just don’t die.

While the best idea right now is an Astro van, we’re also considering other AWD vehicles: an AMC Eagle would be cool, and I think RedBull has a few Suzuki X-90s sitting around. An M35 Deuce And A Half would be fun. A US Mail Truck would probably last forever, and if we go with the semi-trailer concept we would probably want a smaller vehicle on site wherever we park the truck. Current options for this parasitic vehicle include a Nash Metropolitan, a Trabant, a Citroen 2CV, a Renault Dauphine, a Lada, or a Yugo. Yes, they’re all ridiculous but they’re small and can fit in the back of a semi trailer.

It’s still an idea we’re throwing around, but we really need a reason to have a van before we go out and build a hackaspace on wheels, a zombie survival van, or something to launch off some sweet ramps. We don’t go to that many events, and driving a crappy old van across the country a few times a year sounds like fun but surely isn’t.

You can check out [Caleb]’s pitch video for the zombie survival van below.

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Lantern Made In Preparation of Zombie Apocalypse

[BenN] was at his local hackerspace one day when a friend stopped by and offered him a used 5AH lead acid battery. As any good tinkerer would, he jumped on the opportunity and immediately started looking around for a project to use the battery in. One of [BenN’s] recent other projects involved 12volt landscaping lights, the same voltage as the battery he was just given. At this point it was clear that he had a good start to making a lantern. This lantern project also supports [BenN’s] obsession with hobby of preparing for the zombie apocalypse.

A lantern needs an enclosure. Over on the hackerspace’s spare-parts rack was an old ATX power supply. All of the internal electrical components were removed to make room for the battery which fit inside nicely. The landscaping light just happened to be slightly larger than the power supply’s fan cut outs. Once the grill was removed from the metal power supply enclosure, the lamp fit in nicely and was secured using silicone glue which can tolerate any temperature the bulb can produce.

The feature that separates a lantern from a flashlight is the top-mounted carrying handle and this lantern will receive one made from the wiring removed from the ATX power supply. The electrical wiring is fairly straight forward. The battery is connected to the landscaping light by way of the original ATX on/off switch. The two terminals of the battery were also wired to the power supply’s AC input connector. This allows [BenN] to connect a DC battery charger to two of the three pins in order to charge the battery. Although this is a creative way to re-use the AC connector, it leaves quite a bit of potential to accidently plug in a 120v AC cord!


The Walking Dead Survival Box for the Zombie Apocalypse 

When the world comes to an end and zombies run through the streets like a blood thirsty disease, it will be absolutely necessary to store a weapon (or five) away just in case an undead creature tries to get inside. In addition, stopping crooks from ransacking back up supplies will also be a primary concern as well as savage, brain-eating beasts take over the cities. Keeping objects safe with a lock box like this one would deter both undead creatures and mischievous thieves. Or at least that is what was going on in [Mattt Reamer’s] head when he took on this build.

[Matt] is a UX designer who drew inspiration from the wildly popular television series The Walking Dead. He even 3D printed the Walking Dead’s logo on the front of the blood stained box attributing the idea to the show.

The setup here uses an Arduino Uno which is powered by a 9-Volt battery. The fingerprint scanner unlocks the box by verifying the print against a reverence copy stored in the code. When the program authorizes the scan, a servo opens up the latch allowing the contents within to be retrieved. Video of the full system can be seen after the break.

Now all that comes next would be to protect those fingers.

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Preparing for the zombie apocalypse

Every reasonable person prepares for the future. Whether it’s matching your employer’s 401k contributions, making sure you have bread and milk before a snow storm, or saving for your kid’s college fund, planning for the future gives you a comfortable life. [Gord] has exceptional foresight; he build an awesome Louisville Decapitron for the upcoming zombie apocalypse.

It’s an urban legend that a bullet to the brain will stop a zombie. Instantaneous trepanation is devastating in the living, but we’re talking about the undead here. A melee weapon is what you’re after, and you’ve got to cut off the head. [Gord] based his project around a Louisville Slugger. The blade is a 20 inch long piece of plasma cut mild steel. It’s just a prototype to get the balance figured out; the final version will be done in carbon steel.

The tang of the blade fits into two notches in the bat. The blade is secured with two custom fabricated spacers that are perpendicular to the blade. We’re not quite sure of the nomenclature of the resulting weapon (it’s some type of battle axe, we’re sure), but we couldn’t think of a better way to decapitate the undead.