Fail Of The Week: Machining Bismuth

August 24, 2016 by Jenny List 62 Comments

[David Cook]’s summary below the write-up of his experiences working with a bismuth ingot is succinct.

“I wasted a weekend learning why elemental bismuth is not commonly used for metal parts.“

It’s a fair assessment of his time spent growing unspectacular bismuth crystals, casting a bismuth cylinder that cracked, and machining bismuth only to be left with a very rough finish. But even though he admits the exercise was unsuccessful, he does provide us with a fascinating look at the physical properties of the element.

This is what [David] wanted to make. Alchemist-hp + Richard Bartz with focus stack. (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Bismuth is one of those elements you pass by in your school chemistry lessons, it has applications in machining alloys and as a lead replacement but most of us have never knowingly encountered it in the real world. It’s one of the heavy metals, below antimony and to the right of lead on the Periodic Table. Curious schoolchildren may have heard that like water it expands on solidifying or that it is diamagnetic, and most of us have probably seen spectacular pictures of its crystals coated in colourful iridescent oxides.

It was a Hackaday story about these crystals that attracted [David] to the metal. It has a low enough melting point – 271.5 °C – that it can be liquified on a domestic stove, so mindful of his marital harmony should he destroy any kitchen appliances he bought a cheap electric ring from Amazon to go with his bismuth ingot. and set to work.

His first discovery was that cheap electric rings outdoors aren’t very effective metallurgy furnaces. Relocating to the kitchen and risking spousal wrath, he did eventually melt his bismuth and pick off the top layer once it had resolidified, to reveal some crystals.

Unfortunately for him, instead of spectacular colors and huge crystals, the sight that greeted him was one of little brilliance. Small grey crystals with no iridescence. It seems the beautiful samples are made by a very slow cooling of the liquid bismuth, followed by a quick pouring off of the remaining molten metal. Future efforts, he assures us, will involve sand-insulated molds and careful temperature monitoring.

Undeterred, he continued with his stock of bismuth and embarked on the creation of a cylinder. Early efforts with a clay mold resulted in cracked cylinders, so in desperation he cast the entirety of the metal in an aluminium baking tray and cut the resulting ingot to a rough piece of stock for turning.

With the bismuth in the lathe, he then came face to face with what he alluded to in his conclusion above, why machined bismuth parts aren’t something you’ll encounter. His cylinder came out with significantly rough patches on the surface, because bismuth is both crystalline and brittle. He suggests improvements could be made if the metal could be solidified with fewer crystals, but it’s obvious that elemental bismuth on its own is not a winner in the turning stakes.

We suggest you take a look at [David]’s write-up. It may be presented as a Fail of The Week here, but in fact it’s more of a succession of experiments that didn’t work than an unmitigated disaster. The result is an interesting and well-documented read that we’re sure most Hackaday readers will gain something from.

Aside from the bismuth crystals linked to above, we’ve featured bismuth a few times here at Hackaday. A low-temperature soldering process used it in an alloy, and we’ve even featured someone using it in another alloy to print using a RepRap.

Thanks [nebk] for the tip.

Colossus: Face To Face With The First Electronic Computer

August 23, 2016 by Jenny List 46 Comments

When the story of an invention is repeated as Received Opinion for the younger generation it is so often presented as a single one-off event, with a named inventor. Before the event there was no invention, then as if by magic it was there. That apple falling on Isaac Newton’s head, or Archimedes overflowing his bath, you’ve heard the stories. The inventor’s name will sometimes differ depending on which country you are in when you hear the story, which provides an insight into the flaws in the simple invention tales. The truth is in so many cases an invention does not have a single Eureka moment, instead the named inventor builds on the work of so many others who have gone before and is the lucky engineer or scientist whose ideas result in the magic breakthrough before anyone else’s.

The history of computing is no exception, with many steps along the path that has given us the devices we rely on for so much today. Blaise Pascal’s 17th century French mechanical calculator, Charles Babbage and Ada, Countess Lovelace’s work in 19th century Britain, Herman Hollerith’s American tabulators at the end of that century, or Konrad Zuse’s work in prewar Germany represent just a few of them.

So if we are to search for an inventor in this field we have to be a little more specific than “Who invented the first computer?”, because there are so many candidates. If we restrict the question to “Who invented the first programmable electronic digital computer?” we have a much simpler answer, because we have ample evidence of the machine in question. The Received Opinion answer is therefore “The first programmable electronic digital computer was Colossus, invented at Bletchley Park in World War Two by Alan Turing to break the Nazi Enigma codes, and it was kept secret until the 1970s”.

It’s such a temptingly perfect soundbite laden with pluck and derring-do that could so easily be taken from a 1950s Eagle comic, isn’t it. Unfortunately it contains such significant untruths as to be rendered useless. Colossus is the computer you are looking for, it was developed in World War Two and kept secret for many years afterwards, but the rest of the Received Opinion answer is false. It wasn’t invented at Bletchley, its job was not the Enigma work, and most surprisingly Alan Turing’s direct involvement was only peripheral. The real story is much more interesting.

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A PDP-11 On A Chip

August 22, 2016 by Jenny List 47 Comments

If you entered the world of professional computing sometime in the 1960s or 1970s there is a high probability that you would have found yourself working on a minicomputer. These were a class of computer smaller than the colossal mainframes of the day, with a price tag that put them within the range of medium-sized companies and institutions rather than large corporations or government-funded entities. Physically they were not small machines, but compared to the mainframes they did not require a special building to house them, or a high-power electrical supply.

A PDP-11 at The National Museum Of Computing, Bletchley, UK.

One of the most prominent among the suppliers of minicomputers was Digital Equipment Corporation, otherwise known as DEC. Their PDP line of machines dominated the market, and can be found in the ancestry of many of the things we take for granted today. The first UNIX development in 1969 for instance was performed on a DEC PDP-7.

DEC’s flagship product line of the 1970s was the 16-bit PDP-11 series, launched in 1970 and continuing in production until sometime in the late 1990s. Huge numbers of these machines were sold, and it is likely that nearly all adults reading this have at some time or other encountered one at work even if we are unaware that the supermarket till receipt, invoice, or doctor’s appointment slip in our hand was processed on it.

During that over-20-year lifespan of course DEC did not retain the 74 logic based architecture of the earliest model. Successive PDP-11 generations featured ever greater integration of their processor, culminating by the 1980s in the J-11, a CMOS microprocessor implementation of a PDP-11/70. This took the form of two integrated circuits mounted on a large 60-pin DIP ceramic wafer. It was one of these devices that came the way of [bhilpert], and instead of retaining it as a curio he decided to see if he could make it work.

The PDP-11 processors had a useful feature: a debugging console built into their hardware. This means that it should be a relatively simple task to bring up a PDP-11 processor like the J-11 without providing the rest of the PDP-11 to support it, and it was this task that he set about performing. Providing a 6402 UART at the address expected of the console with a bit of 74 glue logic, a bit more 74 for an address latch, and a couple of 6264 8K by 8 RAM chips gave him a very simple but functional PDP-11 on a breadboard. He found it would run with a clock speed as high as 11MHz, but baulked at a 14MHz crystal. He suggests that the breadboard layout may be responsible for this. Hand-keying a couple of test programs, he was able to demonstrate it working.

We’ve seen a lot of the PDP-11 on these pages over the years. Of note are a restoration of a PDP-11/04, this faithful reproduction of a PDP-11 panel emulated with the help of a Raspberry Pi, and an entire PDP-11 emulated on an AVR microcontroller. We have indeed come a long way.

Thanks [BigEd] for the tip.

Impostor Syndrome And Individual Competence

August 22, 2016 by Jenny List 24 Comments

When you attend a very large event such as EMF Camp, there is so much going on that it is impossible to catch everything. It’s easy to come away feeling that you’ve missed all the good stuff, somehow you wasted your time, everyone else had complete focus and got so much more out of the event.

In an odd twist, one of the EMF 2016 talks people have been raving about is very relevant to that fear of inability to take in a festival programme. [Jessica Rose] gave a talk about imposter syndrome. A feeling of inadequacy compared to your peers and a constant anxiety at being exposed as a fraud that will probably be very familiar to many readers. As she points out, it’s a particularly cruel affliction in that it affects those people who do have all the skills while the real impostors share an inflated competence in their abilities.

This has significant relevance to many in our community and for a single presentation to get so many people talking about it at an event like EMF Camp means it definitely hit the mark. The full video is embedded below the break. At about half an hour long it’s well worth a look.

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Fly With A Game Boy Classic

August 21, 2016 by Jenny List 16 Comments

How many grown-up hardware hackers whiled away their youth playing Tetris or Mario on their Game Boy? Fond memories for many, but unless you are lucky your Game Boy will probably be long gone. Not for [Gautier Hattenberger] though, he had an unexpected find at his parents’ house; his Game Boy Classic, unloved and forgotten for all those years. Fortunately for us his first thought was whether he could use it as a controller for a drone, and better still he’s shared his work for all of us to see.

Back in the day a would-be Game Boy hacker would have been deterred by Nintendo’s legal defences against game piracy, but with the benefit of a couple of decades the handheld console’s hardware is now an open book. Unfortunately for [Gautier], he seems to be the first to use one as a flight controller, so he had to plough his own furrow. His Game Boy Game Link serial port feeds an Arduino/FTDI combination that converts Game Link to USB, which is then sent to his laptop on which a small piece of software converts them to commands for the drone through the Paparazzi UAV framework.

All his code is in a GitHub repository, and he’s posted a video of his work which you can see below the break. For a child of the early ’90s, the mere thought that their handheld console could do this would have been mindblowing!

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Pokémon Center Charging Station

August 20, 2016 by Jenny List 18 Comments

If you watch Pokémon Go enthusiasts, you may have noticed something of a community spirit among gamers congregating at busy in-game locations. [Spencer Kern] wanted to encourage this, so produced what he describes as a water cooler for Pokémon Go players, a Pokémon-styled charging station with multiple USB ports.

His build centres on a Yeti 400 solar power pack and a large multi-port USB hub, for which he has built a detailed wooden housing in the style of a Pokémon Center from the earlier Nintendo games. The idea is that gamers will congregate and plug in their phones to charge, thus bringing together a real-world social aspect to the game. We can see the attraction to gamers, however we suspect most Hackaday readers would join us in not trusting a strange USB socket and using only a USB cable not equipped with data conductors.

Still, the housing has seen some careful design and attention to detail in its construction. He started with a 3D CAD model from which he created a set of 2D templates to print on paper and from which to cut the wood. As many of his dimensions as possible were taken from common wood stock to save machining time, and the structure was assembled using wood glue before being sanded and filled. Finally, the intricate parts such as the Pokémon logo were 3D printed, and spray painted. The result is a pretty good real-world replica of the Pokémon Center that you’d recognise if you were a player of the original games, and he reports it was a hit with gamers in his local park.

We’ve covered quite a few Pokémon Go hacks recently, but many of them have had a less physical and more virtual basis. We did see a real-world Pokémon-catching Pokéball though, and of course there was also the automated Pokémon egg incubator.

Thanks [Genki] for the tip.

[Ken Shirriff] Demystifies BeagleBone I/O

August 19, 2016 by Jenny List 15 Comments

If you have ever spent a while delving into the bare metal of talking to the I/O pins on a contemporary microprocessor or microcontroller you will know that it is not always an exercise for the faint-hearted. A host of different functions can be multiplexed behind a physical pin, and once you are looking at the hardware through the cloak of an operating system your careful timing can be derailed in an instant. For these reasons most of us will take advantage of other people’s work and use the abstraction provided by a library or a virtual filesystem path.

If you have ever been curious enough to peer under the hood of your board’s I/O then you may find [Ken Shirriff]’s latest blog post in which he explores the software stack behind the pins on a BeagleBone Black to be of interest. Though its specifics are those of one device, the points it makes have relevance to many other similar boards.

He first takes a look at the simplest way to access a Beagle Bone’s I/O lines, through virtual filesystem paths. He then explains why relying so heavily on the operating system in this way causes significant timing issues, and goes on to explore the physical registers that lie behind the pins. He then discusses the multiplexing of different pin functions before explaining the role of the Linux device tree in keeping operating system in touch with hardware.

For some Hackaday readers this will all be old news, but it’s safe to say that many users of boards like the BeagleBone Black will never have taken a look beyond the safely abstracted ways to use the I/O pins. This piece should therefore provide an interesting education to the chip-hardware novice, and should probably still contain a few nuggets for more advanced users.

We’ve seen a lot of [Ken]’s work here at Hackaday over the years, mostly in the field of reverse engineering. A few picks are his explanation of the TL431 voltage reference, a complete examination of the 741 op-amp, and his reverse engineering of the 1970s Sinclair Scientific calculator.

We appreciate [Fustini]’s tip on this story.

BeagleBone Black image: BeagleBoard.org Foundation [CC BY-SA 3.0], via Wikimedia Commons.