DMG Lib: Digital Mechanism And Gear Library

July 18, 2012 by Gerrit Coetzee 9 Comments

Reader, [klemens], suggested DMG Lib to us when we posted about a similar site. DMG-Lib is an amazing source of information. It’s primary downside is that a great portion of the text is in a language other than English, though in some ways this is a plus. Latin, Italian, German, and many other languages held the position of being the chief scientific language of the world long before English, and this repository holds entire books about mechanisms in those languages. Some of the books range all the way back to the 1500s. The mechanism animations are very good on this site and play smoothly. While it’s a little harder to search than KMODDL due to the language oddities, it’s still an extremely useful and interesting site to add to the hacker’s information toolbox.

Scratch-built Railroad Crossing Signal

July 16, 2012 by Mike Szczys 7 Comments

At first glance you would think this is the real thing, but [Kevin] built this railroad crossing signal from parts you can find at the home store. We keep seeing traffic lights used as web-connected signaling devices. This would be right at home for that type of setup, but [Kevin] built it with railroad enthusiasts in mind.

He used Google SketchUp to design the frame for the signal, then purchased all of the PVC parts to match those specifications. Some grey spray paint goes a long way to making it look like steel tubing. But this is much easier to work with and he should have no trouble internalizing the wiring later on. The lights themselves are tail lights for a trailer with a decorative trim piece added. He designed his own driver board to switch the lights and ring the doorbell which give the signal some sound. His first version used a 555 timer, this one upgrades to microcontroller. We like what he’s doing in the video after the break, but think the bell speed needs to be doubled for it to mimick the real thing just about perfectly.

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Repurposing Old HDD Components

July 12, 2012 by Mike Nathan 32 Comments

hdd-stepper

[IronJungle] had an old hard drive taking up space in his workshop, so he took it apart and wrote in to remind us how useful these old pieces of hardware can be. Aside from offering up incredibly strong magnets and donut-shaped mirrors, HDDs also come with a reliable stepper motor in tow.

He pulled theold drive apart, wiring up two of the stepper motor pins to a pair of the drive’s header pins. This allowed him to easily access the signals produced by the stepper simply by hooking up a small JST connector to the back of the drive.

From there, he can use the drive for any number of purposes. For the sake of discussion, [IronJungle] used it to flash an LED as seen in the video below – something he willingly admits is no great feat. However, stepper motors can be used for in a wide array of projects, both simple and complex. Be sure to share your favorite use for salvaged HDD motors in the comments.

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Two-stage Rocket Climbs To 15 Km, Promptly Gets Lost

July 11, 2012 by Brian Benchoff 34 Comments

Last month, the Cambridge University Spaceflight society launched two stages of their Martlet 1 three-stage rocket. After seeing our call for rocket builds, they sent in a launch report. We’re glad they did; it’s an amazing piece of work that screams into the atmosphere faster than the speed of sound.

The society is designed the three-stage Martlet 1 with the goal of reaching 15km (50,000 feet) over a launch range at Ben Armine in Scotland. This launch was a test of stage separation, intended to work out any bugs in the system before going to the full-sized rocket.

When Martlet 1 takes off, it’s 1st stage engine fires for 5 seconds and coasts for another 9 seconds. In the video after the break, the guys expected to hear the pop of the second stage igniting after 14 seconds. The team forgot to account for the fact the rocket would be 3km in the air at that time, and thanks to the slowness of sound the second stage was heard though the clouds at 25 seconds after launch.

With rockets, hardly anything goes exactly as planned, so unfortunately the team only recovered the bottom half of their rocket. After searching over 60 square km for the second stage, the guys realized it might be lost to the moors of Scotland. Hopefully the second stage will turn up soon so the full 3 stage stack can be realized.

Check out the launch videos after the break.

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Data Mining And Saving Money With Octopart’s Historical Pricing

July 6, 2012 by Brian Benchoff 6 Comments

[Greg Shikhman] is at Octopart this summer as a software development intern. In between the time he’s spending getting coffee for the other devs, he came up with historical pricing for thousands of components available at Octopart

There’s a lot of cool data out there, like this bit of pricing info for a 555 timer. We’re guessing a few people were out of stock of 555s around the end of May, explaining why they were selling (well, available for) $1.68 a piece. If you’re trying to source components, it might be worth your while to check out Octopart’s historical price index. Buying a PIC microcontroller last August was a roll of the dice; in one day the price changed from $5 to just over $2.

With all this data, it’s even possible to data mine for real life events unrelated to shipping and stocking issues. Japanese manufacturer Renesas was hit pretty hard by last year’s earthquake, and this shows up in the historical prices for one of their microcontrollers. Not bad for an intern’s project.

Anti-Sanecraft ARTillery Cannon Is Farm Boy Engineering At Its Finest

July 5, 2012 by Jesse Congdon 13 Comments

The term “just enough knowledge to be dangerous” comes immediately to mind with this one. The official description is “a large scale pan and tilt propane Flame Effect” but that hardly does this thing justice. The Anti-Sanecraft ARTillery Cannon is a three-barrel fire cannon that can move around like its namesake and launch massive propane bursts from two 1″ diameter barrels. The third barrel is somewhat special, it is constructed of stronger steel and can be pre-fed with oxygen to create one massive intense propane-O2 mixed fire burst.

The trick about the whole thing is that when oxygen and propane are mixed it is a highly volatile and dangerous thing, in a closed space they classify as an explosive. Instead oxygen is filled directly into the open ended barrel separately and is allowed to sit until propane fires it out. This mixes the two fuels in the open air where it is safer and far away from any bystanders. We would not suggest you try this at all ever, as the effect was so loud during the Transformus festival that neighbors, miles away from the large festival ground, were complaining about rattling windows. This is the kind of place where several thousand watt sound systems are pushed near the red with no issue, just to give a bit of a comparison.

~~We can’t seem to find a video of this thing in action either~~ [Beyond Joy] just posted a video of this crazy contraption in action (without the O2 effect), check it out after the jump! Don’t forget to check the facebook photo album for all the NPT pipe fitting action, (warning some images of the phallic controls are very mildly NSFW).

Photo Credit: [Bert Reed Photography]

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The Cool Kids All File Their Resistors For Accuracy

July 5, 2012 by Mike Szczys 43 Comments

Here’s a tip to keep in your back pocket, you can use a metal file to adjust your resistors. [Gareth] shows off this technique in the video after the break. A metal file is literally all that you need to do some fine tuning. Just make sure you’re starting off with a carbon film resistor as this will not work with the metal film variety.

His example shows a 10k resistor which is reading just 9.92k on his multimeter. But he needs precisely 10k. After getting through the protective layer he makes just a couple of passes with a small file, each time adding about 20 Ohms of resistance. Now he does mention that excessive deep cuts can hurt the power rating of the resistor. But this certainly isn’t damaging it if done correctly. It turns out this is how they are tuned at the factory.

One possible use he mentions is trimming the balance on a hacked servo motor.

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