Repurposed Plastic Protects PCBs

June 6, 2019 by Brian McEvoy 28 Comments

An errant wire snipping across the wrong electrical pins spells the release of your magic smoke. Even if you are lucky, stray parts are the root of boundless malfunctions from disruptive to deadly. [TheRainHarvester] shares his trick for covering an Arduino Nano with some scrap plastic most of us have sitting in the recycling bin. The video is also after the break. He calls this potting, but we would argue it is a custom-made cover.

The hack is to cut a bit of plastic from food container lids, often HDPE or plastic #2. Trim a piece of it a tad larger than your unprotected board, and find a way to hold it in place so you can blast it with a heat gun. When we try this at one of our Hackaday remote labs and apply a dab of hot glue between the board and some green plastic it works well. The video suggests a metal jig which would be logical when making more than one. YouTube commenter and tip submitter [Keith o] suggests a vacuum former for a tighter fit, and we wouldn’t mind seeing custom window cutouts for access to critical board segments such as DIP switches or trimmers.

We understand why shorted wires are a problem, especially when you daisy-chain three power supplies as happened in one of [TheRainHarvester]’s previous videos.

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Tokyo Mechanical Keyboard Meetup Knocks Our Clacks Off

June 5, 2019 by Kerry Scharfglass 7 Comments

Just a few days ago, on the other side of the planet from this author, there was a mechanical keyboard meetup in Tokyo. Fortunately through the magic of the Internet we can all enjoy the impressive collection of devices people brought, and boy were there some interesting specimens. There were certainly the inevitable collections of strange artisan keycaps, unusual handmade switches, and keycap sets only available in one group buy five years ago in Nicaragua. But among the bright colors were some truly unique custom designs the likes of which we haven’t see before. A single source is hard to credit, you could check the hashtag #tokyomk6 on Twitter, or [obra]’s thread of photos, or this great blog post (video walkthroughs and photos included) from [romly].

Speaking of [romly], one of their designs stands out as particularly unusual. There are a few things to note here. One is the very conspicuous surface profile of the (clearly totally custom) keycaps themselves. Instead of flat or cylindrical or spherical, these are round. Round like the outside of a log. If we didn’t know better it might look like the entire thing was sculpted or extruded as a single unit. And just below the deck are the perpendicular thumb clusters. Frankly we aren’t sure how to refer to this design feature. The switches are mounted at right angles facing inward so the user places a thumb inside it in a style reminiscent of the DataHand. It’s quite interesting, and we’d be love to know more about what specific functionality it provides.

Another interesting entrant is this keyboard with unusually staggered switches and hexagonal caps (check out the individual markings!). Very broadly there are two typical keyboard layout styles; the diagonal columns of QWERTY (derived from a typewriter in the 1800’s) or the non slanted columns of an “ortholinear” or matrix style layout. By those metrics this is something like an ortholinear keyboard in that its switches overlap their neighbors by half, but the edge to edge close packed caps imply that it might be something else. We’d be very interested to know how typing on this beast would be!

There were so many more awesome designs present at the meetup that this would never end if we tried to document them all. Take a look through the posts and call out anything else too excellent to go unnoticed!

Thanks [obra] for Tweeting about this so we could discover it.

C.H.I.P. Or Z.O.M.B.I.E? We Can’t Decide

June 4, 2019 by Jenny List 58 Comments

Imagine for a moment that you are back in 2015. Radio Shack are going to the wall, Heathkit returning from the dead, and Arduino spliting into two warring Arduinos. And someone has announced a tiny Linux-capable microprocessor board called the C.H.I.P. that will cost only $9. We all thought that last one was pretty cool at the time, didn’t we. Then Heathkit’s new products turned out to be pretty lacklustre, the warring Arduinos merged, and the C.H.I.P? The consensus was that $9 was a tall order for that BoM at the time, and then the Raspberry Pi people gave away a free Pi Zero on the front of a magazine before selling it for £5 ($6.30). It didn’t matter that the C.H.I.P. had a nifty all-in-one screen and keyboard combo called the Pocket C.H.I.P. which was a significant object of desire, the venture lasted for three years before finally hitting the rocks last year.

Now the C.H.I.P. is back, in a crowdfunding campaign fronted by one of its original engineers. It’s been renamed the Popcorn, and it comes in three variants. The Original Popcorn is a compatible C.H.I.P. by any other name, while the Super Popcorn is a much higher-spec machine that comes in quad and octacore variants with AmiLogic SoCs. All three have 32 GB eMMC on board, and the specs are suitably impressive but not out of the ordinary for a 2019 single board computer. Prices are $49, $69, and $89, which takes away that optimistic $9 price tag that made the original so attractive. There is no Pocket C.H.I.P. which is a shame because for us that was the only reason to buy a C.H.I.P, but there is a companion board called the Stovetop that provides Raspberry Pi-style desktop and display interfaces.

We wish them well, but it’s difficult to escape the conclusion that the hardware world has moved on and the window of opportunity has closed. It’s not that these boards are not good ones, more that they now join a plethora of others which come a lot closer to the low price of the original. Still, there remains a C.H.I.P. community still out there, so perhaps that will save the day for them.

We interviewed the C.H.I.P.’s creators back in 2015, and marked its passing last year.

Thanks [Rose] for the tip.

Tearing Apart Pulse Transformer Switches

June 3, 2019 by Brian Benchoff 29 Comments

If you like mechanical keyboards, you like switches. Historically, switches were weird, with strange capacitive rubber dome switches in Topre boards, buckling springs in the IBM Model M, and beamsprings in earlier IBM keyboards. This teardown of an HP signal generator has the weirdest keyboard switches ever. They’re being called pulse transformer switches, but they are the strangest, weirdest, and most complicated keyboard switch we’ve ever seen

Mechanically, these keys are mounted on a 1×5 plastic frame with a plunger that presses down on a (brass?) photoetched plate. Mechanically, this is effectively a metal dome keyboard that simply presses a springy bit of metal against a contact on a printed circuit board. That’s the mechanical explanation, the electrical theory of operation is much, much weirder.

Electrically, this keyboard consists of a printed circuit board with two coils underneath each key. The circuit is wired up so two keys are ‘read’ at the same time with a pulse from a multiplexer. This pulse induces a current in the ‘sense’ coil of two individual keys which is sent to a comparator. If both keys are not pressed, the comparator sees a positive and a negative voltage which cancels out, meaning no keys are pressed. If one key is pressed, the metal dome shorts out the transformer underneath the keyboard, meaning only one voltage is seen by the comparator, and that key is registered as being pressed.

This is some crazy keyboard circuitry, and I do not say that lightly. There are ‘acoustic’ keyboards out there which consist of a row of keys striking a metal bar with an acoustic transducer on each end. By measuring the time it takes for the sound of a keypress to reach either end of the metal bar, a keypress can be registered. This is weird and expensive to build, and it’s still simpler than a pulse transformer switch. Check out the video below.

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How Hard Can It Be To Buy A Computer In Germany And Get It Back Home To The UK?

May 21, 2019 by Jenny List 40 Comments

Some of the best adventures in the world of hardware hacking start in the pub. For three volunteers at the National Museum Of Computing in the UK, [Adam Bradley], [Chris Blackburn], and [Peter Vaughan], theirs started over a pint with an eBay listing for an old computer in Germany. No problem you might think, we’re well used to international parcel shipping. This computer wasn’t a crusty old Commodore 64 though, instead it was a room-sized IBM System/360 Model 20 from the 1960s, complete with the full array of peripherals and what seemed to be a lot of documentation and software media. It would need a Mercedes Sprinter, a large van, to shift it, but that seemed feasible. With a bit of frantic bidding they secured the auction, and set off for Germany to view their purchase.

Arriving at the machine’s location they found a little bit more than they had expected. In an abandoned building on a side street in Nuremburg there was an intact machine room full of the IBM computer cabinets over a false floor with all the machine cabling in place, and the only usable access was through a street door which hadn’t been opened in decades and which was obstructed by the false floor itself. To cap it all they found they’d bought not one but two System/360s, and also unexpectedly a 1970s System/370 Model 125. Clearly this was more than a job for a quick in-and-out with a Sprinter.

What followed became a lengthy saga of repeated trips, van hire, constructing ramps, and moving heavy computer parts to a hastily rented storage unit. Decabling a computer of this size is no easy task at the best of times, and these cables had spent many decades in a neglected machine room. It’s a fascinating read, and a very well-documented one with plenty of photos. The machines now sit in their storage units awaiting a return to the UK, and the trio are soliciting any help they can find to make that happen. So if you happen to own a European haulage company with spare capacity on your Germany — UK route or if you can help them in any way, donate or get in touch with them. We think this project has much more to offer, so we’ll be following their progress with interest.

These three intrepid computer hunters were brought together at The National Museum Of Computing at Bletchley, UK. If you find yourself within range it is an essential place to visit, we did so in 2016.

Fun With Negative Resistance II: Unobtanium Russian Tunnel Diodes

May 16, 2019 by Ted Yapo 24 Comments

In the first part of this series, we took a look at a “toy” negative-differential-resistance circuit made from two ordinary transistors. Although this circuit allows experimentation with negative-resistance devices without the need to source rare parts, its performance is severely limited. This is not the case for actual tunnel diodes, which exploit quantum tunneling effects to create a negative differential resistance characteristic. While these two-terminal devices once ruled the fastest electronic designs, their use has fallen off dramatically with the rise of other technologies. As a result, the average electronics hacker probably has never encountered one. That ends today.

Due to the efficiencies of the modern on-line marketplace, these rare beasts of the diode world are not completely unobtainable. Although new-production diodes are difficult for individuals to get their hands on, a wide range of surplus tunnel diodes can still be found on eBay for as little as $1 each in lots of ten. While you’d be better off with any number of modern technologies for new designs, exploring the properties of these odd devices can be an interesting learning experience.

For this installment, I dug deep into my collection of semiconductor exotica for some Russian 3И306M gallium arsenide tunnel diodes that I purchased a few years ago. Let’s have a look at what you can do with just a diode — if it’s the right kind, that is.

[Note: the images are all small in the article; click them to get a full-sized version]

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A Full-Stack Web Browser

May 14, 2019 by Brian Benchoff 13 Comments

Interviewing to be a full-stack engineer is hard. It’s a lot harder than applying for a junior dev job where you’re asked to traverse a red-black tree on a whiteboard. For the full-stack job, they just give you a pile of 2N2222 transistors. (The first company wasn’t a great fit, and I eventually found a place that gave me some 2N2907s for the interview.) That said, there’s a certain challenge in seeing how far you can push some doped silicon. Case in point, [Alastair Hewitt]. He’s building a computer to browse the world wide web from the gate level up.

The goal of this project is to browse the web using only TTL logic. This presents problems that aren’t readily apparent at first glance. First up is being able to display text on a screen. The easiest way to do this now is to get a whole bunch of modern memories that are astonishingly fast for a 1970s vintage computer. This allows for VGA output, and yes, we’ve seen plenty of builds that output VGA using some big honkin’ memories. It turns out these RAM and ROM chips are a little better than the specs say they are, and this computer is overclocked from the very beginning.

A bigger problem is how to interface with a network. This is a problem for very old computers, but PPP still exists and if you have the software stack you can read something from a server over a serial connection. [Alistar] actually found the UART frequency was more important than the dot clock frequency of VGA, and the system clock must therefore be built around the serial port, not the display interface. This means the text mode interface is actually 96 columns instead of the usual 80 columns.

It’s very easy to say that you’re building a computer on a bread board. It’s another thing entirely to actually do it. This is actually a surprisingly well-though out sketch of a computer system that will, theoretically, be able to connect to the Internet. Of course, the reality of the situation is that this computer will be connecting over serial to a computer that’s connected to the Internet, but there’s no shame in that. You can check out the progress on the GitHub for this project.