3 things to talk about today: - RFIDs - prep for Beth Noveck - Final

Questions from Last Week

ZachSwartz.com asked "Why are there different forms of wifi?"

There are different frequencies and different protocols (Manchester encoding, etc.).
The pursuit is always to try to increase speed and compatibility.


Passive RFIDs

Passive RFIDs are built from an integrated circuit with an antenna. produce no power on its own. They get induced power from radio waves that travel through the circular antenna. uses the power from the transmitters broadcast to respond. can't hold much info. range is minimal.

To improve usable range either increase the power of the reader or make the antenna more sensitive to incoming frequencies.

Example - myfair tags: flexible type tag round in merchant applications. ISO standardized (ISO 14443). holds about 1k of info.

Active RFIDs

tag is powered. gives better range and more bandwidth.

Example - EZ-Pass


Active RFID. No dedicated roles of receiver or transmitter, with NFC each node can be both. can both be read and make contact by using a microcontroller.

NFC can be set up as 'proactive' telling other nfc devices to switch to listen mode.

More Info on RFIDs

  • companies make proprietary protocols for transmission. Often for security purposes such as Blink cards which are used for payment. Differing protocols lead to less interoperability.
  • RFIDs transmit in a cardioid pattern. Visualization of RFID range
  • arrays of tags can be used to determine location of reader laden objects.
  • FCC regulates passive RFID tags and receivers.
  • The size and shape of the antenna of an RFID tag determines what frequency(ies) it responds to.
  • A large antenna has dead spots, so to cover a wide area one needs to use many smaller antennae.
  • RFID had an origin in World War II for friend and foe identification of aircraft.

Communications and Protocol - most protocols are a-synchronous serial, operating at 9600bps. - Arduino uses I2C (synchronous serial).


Greg: package tracking

How do we get packages to inform the receivers that the packages have arrived on the floor? Discussed the balance of privacy issues with accessibility to the system. Tom mentioned that 90% of packages would be scannable/readable easy-to-handle but dealing with the remaining 10% of packages (with handwritten labels or oddly shaped) would require much of the work. The USPS delivers to NYU's main mail sorting location and makes corresponding tracking numbers say delivered before they reached the floor. So the system would have to be smarter than just following tracking numbers. determined that this would most likely require a diligent human component.

Dave - expertise and knowledge in groups.

we have lots of knowledge to share but we don't always know who they are and what their availability is.

Gabriella - map of floor.

heat based visualization of peoples' location.


Tom suggests focusing on: - sharing resources on the floor. - motifvation to seek out resources. - physical interface. - Getting to know existing infrastructure before building something new.

  • goal for next week - figure out where you fit into this project.

Beth Noveck Tom wants Beth here because: - she is a hopeless idealist. - she's good at starting discussion (instead of just fielding comments). - she doesn't know how to make what she wants, but she makes it anyway. She focuses on what's wrong with the discussion. - quality of discussion. quality of data.