Distributed computing in JavaScript

mapreduce

We’ve heard about the idea of using browsers as distributed computing nodes for a couple years now. It’s only recently, with the race towards faster JavaScript engines in browsers like Chrome that this idea seems useful. [Antimatter15] did a proof of concept JavaScript implementation for reversing hashes. Plura Processing uses a Java applet to do distributed processing. Today, [Ilya Grigorik] posted an example using MapReduce in JavaScript. Google’s MapReduce is designed to support large dataset processing across computing clusters. It’s well suited for situations where computing nodes could go offline randomly (i.e. a browser navigates away from your site). He included a JavaScript snippet and a job server in Ruby. It will be interesting to see if someone comes up with a good use for this; you still need to convince people to keep your page open in the browser though. We’re just saying: try to act surprised when you realize Hack a Day is inexplicably making your processor spike…

[via Slashdot]

Mobile RFID scanning

[Chris Paget] is going to be presenting at ShmooCon 2009 in Washington D.C. this week. He gave a preview of his RFID talk to The Register. The video above demos reading and logging unique IDs of random tags and Passport Cards while cruising around San Francisco. He’s using a Symbol XR400 RFID reader and a Motorola AN400 patch antenna mounted inside of his car. This is industrial gear usually used to track the movement of packages or livestock. It’s a generation newer than what Flexilis used to set their distance reading records in 2005.

The unique ID number on Passport Cards doesn’t divulge the owners private details, but it’s still unique to them. It can be used to track the owner and when combined with other details, like their RFID credit card, a profile of that person can be built. This is why the ACLU opposes Passport Cards in their current form. The US does provide a shielding sleeve for the card… of course it’s mailed to you with the card placed outside of the sleeve.

Technology exists to generate a random ID every time an RFID card is being read. The RFIDIOt tools were recently updated for RANDOM_UID support.

[Thanks Zort]

RepRap pinch wheel extruder

pinchwheel

What you see above is the culmination of [Zach Smith]‘s work building a pinch wheel style extruder for the RepRap. The current RepRap 3D printer uses a screw mechanism to push 3mm polymer filament into a heating barrel where it is melted and then extruded through a fine nozzle. [Zach]‘s new version uses a drive gear from SDP/SI mounted directly to the DC motor we saw him teardown earlier. He’s redesigned the carrier for the extruder as well. It’s now much lighter and has provisions for mounting current and future controller electronics along with a magnetic rotary encoder. In the last two days, he’s been doing real world testing. It’s been doing well, but he’s learning to do things like always using a full spool and not trying to run short lengths back to back.

Electric spinning wheel

spinningwheel

[glacialwanderer], who you may remember from his CNC machine build, recently completed an electric spinning wheel. Spinning wheels are used by knitters to turn raw sheep’s wool into yarn. He went through several iterations before arriving at a good design. Besides the motor, there are two major components to the spinning wheel: the flyer and the bobbin. A Scotch tension brake is used to slow the rotation of the bobbin in relation to the flyer. This causes the wool to twist as it’s pulled on.

He initially tried to just use a dimmer switch with an AC motor. That quickly burnt up. The next version used a sewing machine motor since they’re designed with a variable speed control. Unfortunately, it didn’t have enough torque at low speeds. The final design used a DC motor with a SyRen motor controller. It offered plenty of power and at ~$150 it’s still less than the cheapest commercial models on eBay. You can see a video of it and the spinning process embedded below.

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