A Mini-ITX PDP-11

April 26, 2018 by 36 Comments

The PDP-11 is perhaps the most important computer in history. This was the king of all minicomputers, and once you get past the amazing front panels of the 11/20, 11/40, and 11/70, you’ll find PDP-11s everywhere. Heathkit sold one. It was the smallest computer that could run Unix. There were desktop versions sold as DEC Professionals. I have been told Ticketmaster — the entire backend of all event ticket sales in the United States — still runs on PDP-11s.

One of the interesting bits of the PDP-11 is the miniaturization that happened over the course of its development. Over time, the Unibus processor cards of the earlier models were shrunk down into a single chip. This PDP-on-a-chip was then cloned by the Soviets, and like most vintage Eastern European electronics, they’re all readily available on eBay.

For his Hackaday Prize entry, [SHAOS] is taking one of these chips and turning it into a modern machine. The PDPii is a project to bring the PDP-11 back to life in the form of an Open Source motherboard with a Mini-ITX motherboard. Is it game-changing? No, not really; you could buy a desktop PDP-11 thirty years ago. This project, though, is taking new old stock chips you can buy for ten dollars and turning it into something resembling a modern system. Finally, Ticketmaster can upgrade.

The design of this project doesn’t quite meet the spec for the Mini-ITX form factor; it’s based off the RC2014 backplane Z80 computer, but desktop computer cases are cheap, as are power supplies, and I’m sure someone out there knows how to fit an eight inch floppy in a five and a quarter inch hole.

The key feature for this Mini-ITX backplane PDP-11 is a redesign of the Q-bus found in later PDPs to something that’s a bit smaller, a bit cheaper to manufacture, and still has all the relevant pins accessible. With some reconfiguring of the baroque DEC standards, [SHAOS] came up with the Bread-Board Friendly Q-bus Extended, or BBQ-Bus+. The next step for this project is gathering up a few PDP-11 compatible Russian КР1801ВМ2 CPUs and going to town on the architecture of what is probably the most replicated computer design ever.

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Is It On Yet? Sensing The World Around Us, Starting With Light

April 26, 2018 by 10 Comments

Arduino 101 is getting an LED to flash. From there you have a world of options for control, from MOSFETs to relays, solenoids and motors, all kinds of outputs. Here, we’re going to take a quick look at some inputs. While working on a recent project, I realized the variety of options in sensing something as simple as whether a light is on or off. This is a fundamental task for any system that reacts to the world; maybe a sensor that detects when the washer has finished and sends a text message, or an automated chicken coop that opens and closes with the sun, or a beam break that notifies when a sister has entered your sacred space. These are some of the tools you might use to sense light around you.

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Writing On A Whiteboard, Performed By A Robot

April 26, 2018 by 6 Comments

For some of us here at Hackaday, school is but a very distant memory. All that teenage awkwardness we’d rather forget, synth pop, and 8-bit computers were cool the first time around, and our newer classrooms didn’t have blackboards any more. The Whiteboard Future Had Arrived, and it came with solvent-laden pens that our more rebellious classmates swore would get you high if you sniffed them for long enough. Innocent times. Kids nowadays probably get their lessons from iPads, but the whiteboard isn’t finished just yet. [f4hdk] has updated his board with Scribot, a whiteboard-writing robot arm driven by a couple of stepper motors and a nicely-engineered set of belts, that writes text from ASCII files in a custom-designed vector font.

At the end of the arm is a whiteboard marker, and in a neat twist it has an eraser on its rear end. A quick flip of the servo holding the marker, and it can rub out any of its work. Behind it all is an LPC1789 Cortex M3-based Mbed board with appropriate servo driver boards, and for those curious enough to take a second look there is a full code repository. The result as you can see in the video below the break is a very well-executed whiteboard writer. Your 1980s teacher might have grumbled at the new technology, but certainly couldn’t accuse it of doing a bad job!

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Mechanisms: The Lever, It’s Everywhere

April 26, 2018 by 28 Comments

Levers are literally all around us. You body uses them to move, pick up a pen to sign your name and you’ll use mechanical advantage to make that ballpoint roll, and that can of soda doesn’t open without a cleverly designed lever.

I got onto this topic quite by accident. I was making an ornithopter and it was having trouble lifting its wings. For the uninitiated, ornithopters are machines which fly by flapping their wings. The problem was that the lever arm was too short. To be honest, as I worked I wasn’t even thinking in terms of levers, and only realized that there was one after I’d fine-tuned its length by trial and error. After that, the presence of a lever was embarrassingly obvious.

I can probably be excused for not seeing a lever right away because it wasn’t the type we most often experience. There are different classes of levers and it’s safe to say that most people aren’t even aware of this. Let’s take a closer look at these super useful, and sometimes hidden mechanisms known as levers.

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Turn Failed Prints Into Office Fun With A Paper Airplane Maker

April 26, 2018 by 11 Comments

If you’re anything like us, you feel slightly guilty when you send a job to a printer only to find that twenty pages have printed wrong. Maybe it’s a typo, maybe it’s the dreaded landscape versus portrait issue. Whatever it is, trees died for your mistake, and there’s nothing you can do about it except to recycle the waste. But first, wipe that guilt away by using this one-stroke paper airplane maker to equip the whole office for an epic air battle.

We have to admit, automated paper handling has always fascinated us. The idea that a printer can reliably (sometimes) feed individual sheets of a stack is a testament to good design, and don’t even get us started about automatic paper folding. [Jerry de Vos]’ paper airplane maker doesn’t drive the sheets through the folder — that’s up to the user. But the laser-cut plywood jig does all the dirty work of creating a paper airplane. The sheet is clipped to an arm that pulls the paper through a series of ramps and slots that force the paper gently into the five folds needed for the classic paper dart. It’s fascinating to watch, and even though everyone seems to be using it very gingerly lest the paper tear, we can see how adding some rollers and motors from a scrapped printer could entirely automate the process. Think of the fun a ream of paper could provide around the office then.

Oh, wait…

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Neural Network Names Nightshades

April 26, 2018 by 12 Comments

Neural networks are a core area of the artificial intelligence field. They can be trained on abstract data sets and be put to all manner of useful duties, like driving cars while ignoring road hazards or identifying cats in images. Recently, a biologist approached AI researcher [Janelle Shane] with a problem – could she help him name some tomatoes?

It’s a problem with a simple cause – like most people, [Darren] enjoys experimenting with tomato genetics, and thus requires a steady supply of names to designate the various varities produced in this work. It can be taxing on the feeble human brain, so a silicon-based solution is ideal.

[Janelle] decided to use the char-rnn library built by [Andrej Karpathy] to do the heavy lifting. After training it on a list of over 11,000 existing tomato varieties, the neural network was then asked to strike out on its own.

The results are truly fantastic – whether you’re partial to a Speckled Garfech or you prefer the smooth flavor of the Golden Pow, there’s a tomato to suit your tastes. When the network was retrained with additional content in the form of names of metal bands, the results get even better – it’s only a matter of time before Angels of Saucing reach a supermarket shelf near you.

On the surface, it’s a fun project with whimsical output, but fundamentally it highlights how much can be accomplished these days by standing on the shoulders of giants, so to speak. Now, if you need some assistance growing your tomatoes, the machines can help there, too.

 

Motor Test Bench Talks The Torque

April 25, 2018 by 6 Comments

Salvaging a beefy motor is one life’s greatest pleasures for a hacker, but, when it comes to using it in a new project, the lack of specs and documentation can be frustrating. [The Post Apocalyptic Inventor] has a seemingly endless stockpile of scavenged motors, and decided to do something about the problem.

Once again applying his talent for junk revival, [TPAI] has spent the last year collecting, reverse-engineering and repairing equipment built in the 1970s, to produce a complete electric motor test setup. Parameters such as stall torque, speed under no load, peak power, and more can all easily be found by use of the restored test equipment. Key operating graphs that would normally only be available in a datasheet can also be produced.

The test setup comprises of a number of magnetic particle brakes, combined power supply and control units, a trio of colossal three-phase dummy loads, and a gorgeously vintage power-factor meter.

Motors are coupled via a piece of rubber to a magnetic particle brake. The rubber contains six magnets spaced around its edge, which, combined with a hall sensor,  are used to calculate the motor’s rotational speed. When power is applied to the coil inside the brake, the now magnetised internal powder causes friction between the rotor and the stator, proportional to the current through the coil. In addition to this, the brake can also measure the torque that’s being applied to the motor shaft, which allows the control units to regulate the brake either by speed or torque. An Arduino slurps data from these control units, allowing characteristics to be easily graphed.

If you’re looking for more dynamometer action, last year we featured this neatly designed unit – made by some Cornell students with an impressive level of documentation.

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