rfid

191 Articles

UHF Power Harvesting

January 29, 2009 by 15 Comments

hdpowerharvesting

[Alanson Sample] and [Joshua R. Smith] have been experimenting with wireless power transfer for their sensing platform. Their microcontroller of choice is the MSP430, which we used on our e-paper clock. They chose it specifically for its ability to work with low voltages and they discus its specific behavior at different voltages. The first portion of their paper uses a UHF RFID reader to transmit to the sensor’s four stage charge pump. They added a supercap to provide enough power for 24 hours of logging while the node isn’t near a reader. For the second half of the paper, they use a UHF antenna designed for digital TV with the same circuit and pointed it at a television tower ~4.1km away. It had an open circuit voltage of 5.0V and 0.7V across an 8KOhm load, which works out to be 60uW of power. They connected this to the AAA battery terminals of the thermometer/hygrometer pictured above. It worked without issue. The thermometer’s draw on a lab power supply was 25uA at 1.5V.

It’s an interesting approach to powering devices. Do you have an application that needs something like this? For more on wireless power, checkout this earlier post on scratch building RFID tags.

[via DVICE]

MBTA Drops Lawsuit Against MIT Subway Hackers

December 23, 2008 by 8 Comments

The Massachusetts Bay Transit Authority (MBTA) has dropped its federal case against three MIT researchers, “the subway hackers”. This happened in October and now the EFF brings news that the students will be working with the MBTA to improve their system. The overall goal is to raise security while keeping expenses minimal.

This whole mess started in August when a gag order was issued against the students’ presentation at Defcon. It’s a shame no one ever saw it because it covers a lot of interesting ground. A PDF of the banned slides is still online. They performed several attacks against both the subway’s fare system and physical security. Our favorites by far were using GNU Radio to sniff the RFID card’s transaction and bruteforcing Mifare Classic with an FPGA.

Scratch Built RFID Tags

November 11, 2008 by 17 Comments

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[nmarquardt] has put up an interesting instructable that covers building RFID tags. Most of them are constructed using adhesive copper tape on cardstock. The first version just has a cap and a low power LED to prove that the antenna is receiving power. The next iteration uses tilt switches so the tag is only active in certain orientations. The conclusion shows several different variations: different antenna lengths, conductive paint, light activated and more.

IR Glass Level Detection

November 7, 2008 by 15 Comments

[youtube=http://www.youtube.com/watch?v=DG3_2lvoL8A]

[Johnny Lee]’s colleague [Paul Dietz] has done some interesting work using interactive tables. He’s specifically researched how to determine how full a drink glass is. In the video above, he’s using Microsoft’s Surface, but this technique should work with any IR camera based multitouch table. Determining the drink level requires custom glassware that has a small prism inside. When the liquid level is above the prism, light passes through, but when it’s below the top it reflects more IR light back into the table. Using this information, restaurant staff could serve drinks in a more efficient manner.

[Paul] has worked on another project that uses RFID and capacitive sensing to a similar effect.

DIY RFID Implant

October 15, 2008 by 58 Comments

[youtube=http://www.youtube.com/watch?v=vsk6dJr4wps]

[Quethe] implanted an RFID chip into his hand so that he can access his handgun safe without having to fumble around for keys or buttons. He’s also planning to do more with the chip, including installing readers so he can access his car without keys. [Quethe] claims that inserting the chip hurts less than drawing blood. From the video he’s apparently using livestock grade equipment for the injection. While we applaud his ingenuity, we’re not sure that the convenience of easier access to guns and cars is actually worth the trouble of putting a chip in your body.

We’ve covered quite a a few hackers that have chosen to chip themselves in the past. [Mikey Sklar] did it back in 2005 after constructing a pair of pants to block the signal. [Amal Graafstra] ended up writing RFID Toys after implanting himself. [Larry Pesce] from the PaulDotCom podcast had his chip cloned on stage by [Major Malfunction] at ShmooCon. [Annalee Newitz] had her chip cloned by [Jonathan Westhues] while covering RFID hacking for Wired. It’s interesting to see the practice of DIY RFID chipping gaining traction, and, thankfully, all of the people just listed understand that it’s not a form of security.

[via Boing Boing]