Re: House Access Help

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 31 Jul 2006 11:12:51 -0700, joseph_stiehm@xxxxxxxxx wrote in message
<1154369571.193456.12140@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>Marc,
>
>Thanks a lot for the info.  I was reading up this past weekend.  The
>iAutomate solution is interesting.  A couple of questions if you don't
>mind answering them:
>
>1) The iAutomate (Wavetrend) solution involves tags that are battery
>operated and have a lifespan of 5 years.  Are you aware of any good
>long-range proximity reader solutions which involves strictly passive
>tags that don't require their own power source (HID seems to fit the
>bill, but it doesn't seem to be marketed to home automation)?
>
>2) The setup I have envisioned has the reader installed in the house
>with the read envelope extending outside the house.  All the readers
>I've looked at seems to be omni-directional.  Any ideas on creating a
>hemi-spherical area of activation (on the outside of my house only)?  I
>looked at the front door this weekend with a tape measure.  In order to
>create a passive, transparent solution to opening the door I figured a
>radius of 36" around the doorknob (at wallet level) would be ideal.  I
>don't want to trip the front door reader from the inside so I figured I
>needed to do one of 4 things:
>  a - Shield the reader (using metal?) so it only detects tags from one
>direction. Is this realistic?
>  b - Set up the reader outside (ugly for a number of reasons) so that
>the envelope doesn't penetrate to the inside of the house
>  c - Use a reader and a second, fixed-location, tag set up
>asymmetrically and measure distance of the 1st tag against the distance
>to the second tag to determine whether the door should open (I don't
>even know if this is feasible)
>  d - Get two readers (expensive) and set them up in conjunction to
>create a crescent of activation (tricky?)
>
>Again, I'm new to this so maybe my concern is due to naivete on my part
>(it may be that this is something HA folks simply "deal with"), but
>before I look to spend $700 on the venture I'd like to establish the
>feasibility of my concept.
>
>Thanks for your time.
>
>= Joseph

Joseph,

Sophisticated (expensive) systems with multiple sensors can locate an RFID
tag to within centimeters in 3-D space in real time. This in turn can be
used to calculate diretion and rate of movement (velocity vectors) which
would be very useful to address a goal that I've played with off-and on for
years.

+++

This site has some very useful info:

http://www.antd.nist.gov/wctg/RFID/RFIDassist.htm#Local

++++

Earlier this year, I wrote in ccomp.home.automation about G2 Microsystem's
www.g2microsystems.com new active RFID chip.

' The $12 (in quantity; scheduled to ship 3rd quarter 2006) G2501 chip
performs active RFID over standard 802.11b WIFI.  Battery life using two
AA's is projected at 5 years.

The chip is programmed through a url and "uses existing WIFI wireless
access points on the network, meaning no new network installation is
required" if a WIFI network exists.

Spatial location of the tag to within 15 feet can be accomplished  by
triangulation using three WIFI access points, or to within about six feet
using ISO 24370/ANSI 371.1 Time Delay of Arrival (TDOA).

The chip also has two standard passive RFD technologies built in:
Electronic Product Code (EPC) and a standard 125mhz magnetic. These are
powered internally, don't need the WIFI transceiver to turn on and "can
talk to other existing RFD systems in their neighborhood".

GPIO, UART, SPI, current loop and ADC interfaces are built-in and on-chip.
The latter are specifically designed for sensor interfaces such as
temperature, humidity, light, radiation and so on. '

With respect to the battery issue, I'd work under the assumption that five
years (cited battery life) is a long time in the rapidly evolving long-range
RFID arena. It would be nice to see a device the size and thickness of a
credit card including battery that could be kept in a wallet. With that form
factor, the battery life would not be an issue (for me.) Credit cards all
expire in less than five years, so why shouldn't RFID tags?

There are of course passive RFID tags, but their range is limited. The G2501
chip discussed above can employ both techniques.

HTH ... Marc
Marc_F_Hult
www.ECOntrol.org