There Is No Such Thing As An Invalid Unit

September 19, 2017 by 356 Comments

The Mars Climate Orbiter was a spacecraft launched in the closing years of the 1990s, whose job was to have been to study the Martian atmosphere and serve as a communications relay point for a series of other surface missions. It is famous not for its mission achieving these goals, but for the manner of its premature destruction as its orbital insertion brought it too close to the planet’s atmosphere and destroyed it.

The ill-fated Mars Climate Orbiter craft. NASA [Public domain].
The ill-fated Mars Climate Orbiter craft. NASA [Public domain].
The cause of the spacecraft entering the atmosphere rather than orbiting the planet was found in a subsequent investigation to be a very simple one. Simplifying matters to an extent, a private contractor supplied a subsystem which delivered a reading whose units were in the imperial system, to another subsystem expecting units in the SI, or metric system. The resulting huge discrepancy caused the craft to steer towards the surface of the planet rather than the intended orbit, and caused the mission to come to a premature end. Billions of dollars lost, substantially red faces among the engineers responsible.

This unit cock-up gave metric-using engineers the world over a brief chance to feel smug, as well as if they were being honest a chance to reflect on their good fortune at it not having happened on their watch. We will all at some time or another have made an error with respect to our unit calculations, even though in most cases it’s more likely to have involved a simple loss of a factor of ten, and not with respect to a billion dollar piece of space hardware.

But it also touches on one of those fundamental divides in the world between the metric and imperial systems. It’s a divide that brings together threads of age politics, geography, nationalism, and personal choice, and though it may be somewhere angels fear to tread (we’ve seen it get quite heated before to the tune of 885+ comments), it provides a fascinating subject for anyone with an interest in engineering culture.

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Hybrid Technique Breaks Backscatter Distance Barrier

September 19, 2017 by 31 Comments

Low cost, long range, or low power — when it comes to wireless connectivity, historically you’ve only been able to pick two. But a group at the University of Washington appears to have made a breakthrough in backscatter communications that allows reliable data transfer over 2.8 kilometers using only microwatts, and for pennies apiece.

For those unfamiliar with backscatter, it’s a very cool technology that modulates data onto RF energy incident from some local source, like an FM broadcast station or nearby WiFi router. Since the backscatter device doesn’t need to power local oscillators or other hungry components, it has negligible power requirements. Traditionally, though, that has given backscatter devices a range of a few hundred meters at most. The UW team, led by [Shyamnath Gollokota], describe a new backscatter technique (PDF link) that blows away previous records. By combining the spread-spectrum modulation of LoRa with the switched attenuation of incident RF energy that forms the basis for backscatter, the UW team was able to cover 2800 meters for under 10 microwatts. What’s more, with printable batteries or cheap button cells, the backscatter tags can be made for as little as 10 cents a piece. The possibilities for cheap agricultural sensors, ultracompact and low power wearable sensors, or even just deploy-and-forget IoT devices are endless.

We’ve covered backscatter before, both for agricultural uses and for pirate broadcasting stations. Backscatter also has also seen more cloak and dagger duty.

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In-Band Signaling: Quindar Tones

September 19, 2017 by 29 Comments

So far in this brief series on in-band signaling, we looked at two of the common methods of providing control signals along with the main content of a transmission: DTMF for Touch-Tone dialing, and coded-squelch systems for two-way radio. For this installment, we’ll look at something that far fewer people have ever used, but almost everyone has heard: Quindar tones.

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London Calling: The Hackaday UK Unconference Roundup

September 19, 2017 by 22 Comments

A trip to London, for provincial Brits, is something of an undertaking from which you invariably emerge tired and slightly grimy following your encounter with the cramped mobile sauna of the Central Line, its meandering international sightseers, and stampede of besuited commuters heading for the City. Often your fatigue after such an expedition will be that following the completion of a Herculean labour, but just sometimes it will instead be the contented tiredness of a fulfilling and busy time well spent.

Such will be the state of the happy band of the Hackaday community who made it to London this weekend for our UK unconference held in association with our sponsor, DesignSpark. A Friday night bring-a-hack social in a comfortable Bloomsbury pub, followed by Saturday in an auditorium next to one of the former Surrey Commercial Docks for a day of back-to-back seven-minute talks laying out the varied and interesting work our readers are involved in.

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Music Box Plays “Still Alive” Thanks To Automated Hole Puncher

September 19, 2017 by 20 Comments
Custom hole punch and feed system

Most projects have one or two significant aspects in which custom work or clever execution is showcased, but this Music Box Hole Punching Machine by [Josh Sheldon] and his roommate [Matt] is a delight on many levels. Not only was custom hardware made to automate punching holes in long spools of paper for feeding through a music box, but a software front end to process MIDI files means that in a way, this project is really a MIDI-to-hand-cranked-music-box converter. What a time to be alive.

The hole punch is an entirely custom-made assembly, and as [Josh] observes, making a reliable hole punch turns out to be extremely challenging. Plenty of trial and error was involved, and the project’s documentation as well as an overview video go into plenty of detail. Don’t miss the music box version of “Still Alive”, either. Both are embedded below.

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Single Board Relay Computer

September 18, 2017 by 26 Comments

We all know you can build a computer out of relays, and if you’re a regular reader of Hackaday, you’ve probably seen a few. Actually designing and fabricating a computer built around relays is another thing entirely, and an accomplishment that will put you right up there with the hardware greats.

The newest inductee of the DIY microcomputer hall of fame is [Jhallen]. He’s built a microcomputer ‘trainer’ out of relays. It’s got more click and clack than the Tappet family, and is a work of art rendered in DPDT relays.

The biggest consideration in designing a relay computer is the memory. You can implement a CPU in a few dozen relays, but even a small amount of memory is still hundreds of additional components. In this computer, [Jhallen] is sort of cheating. The memory is implemented as 256 32-bit words on a microcontroller alongside a controller for the front panel. The CPU is still all relays, with support for self-modifying code, a bunch of instructions for conditional jumps, and an ‘increment and jump if not equal to zero’ instruction.

Below, you can check out a very in-depth video of the relay computer in action, starting off with some satisfying click and clack of Euclid’s algorithm and a demonstration of the variable clock rate. The video goes on to demonstrate the assembly language of the relay computer itself and a bit of the overall architecture. This is really one of the most educational demo videos for vintage computing we’ve ever seen.

[Jhallen] assembled a few of these boards and he’s selling some of the extras. If you have $600, you can pick one up over on Tindie (standard Hackaday / Tindie disclosure statement). Considering the amount of soldering required to assemble this board, we’re going to guess that’s a very fair price.
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Sawed Off Keyboard

September 18, 2017 by 45 Comments

Have you ever had to cut a piece of furniture in two to get it into a new place? Yours truly has, having had to cut the longer part of a sectional sofa in two to get it into a high-rise apartment. That’s what [Charles]’ sawed off keyboard immediately reminded us of. It sounds just as crazy, but brilliant at the same time.

In [Charles]’ case he wanted a keypad whose keys were customizable, and that would make a single keypress do common things like cut, copy and paste, which are normally ctrl-X, ctrl-C and ctrl-V in Windows. To do that he literally sawed off the numeric keypad from a full-sized keyboard. He also sawed off the end to the left of the QWERTY keyboard, and glued it onto the open end of his keypad.

The circuit board was too wide to fit in his new keypad, but he couldn’t stretch out the connections from the keypad’s keys to the board. So he did what any self-respecting hacker would do, he cut the circuit board where there were a manageable number of traces, leaving one part that would fit inside the keypad and another part that he could connect the traces to using a few wires. Lastly, he’d started with a PS/2 keyboard but he wanted USB output and programmability. So he redirected the PS/2 wires to an Arduino compatible Pro Micro and wrote some conversion code which you can find on his GitHub.

What other transformations can we do to keyboards? [Shrodingers_Cat] combined his with some DVD case covers to come up with a pedal board for use with his feet. And given that the keys on the numeric keypad are redundant, [Kipkay] put it to use as a hiding place for valuables instead.