[Dprglist] key fob query

Murray Altheim murray18 at altheim.com
Mon May 24 12:00:32 PDT 2021

On 25/05/21 6:26 am, David Anderson via DPRGlist wrote:
> My wife's new car won't let you accidentally lock the remote key
> fob in the car.
> So how does it know the key fob is in the car?
> And does that suggest the fob is transmitting constantly, rather 
> than just when a button is pressed?
> Inquiring minds want to know.
Hi David,

Mine car is the same. I think the fob operates with a button that uses
active RF to lock and unlock, but if I walk up to my car with the fob
in my backpack and pull up on the door handle it will unlock, so it
knows the fob is nearby. I believe it uses RF for the buttons and RFID
for the presence-sensing. RFID devices can be extremely small, as small
as 0.15 x 0.15mm:

   Hitachi Develops World’s Smallest RFID Chip

   SmartDust on Wikipedia

I might have mentioned this in one of our videoconferences awhile back.

The concept has actually been around since the 90s, with Hitachi
publicising their development of it in 2006. The Wikipedia page states:
"The work was strongly influenced by [...] science fiction authors
Stanislaw Lem (in novels The Invincible in 1964 and Peace on Earth in
1985), Neal Stephenson and Vernor Vinge." I found Lem's book Solaris
much different than I'd thought based on the movies, it's actually
about our [in]ability to know anything scientifically.

I was thinking about using something with RFID for a robot dock, or for
the latter-end of waypoint navigation as the range is fairly limited.
There's those longer range RFID-based beacons as well, now for sale from
a store near you.


Murray Altheim <murray18 at altheim dot com>                       = =  ===
http://www.altheim.com/murray/                                     ===  ===
                                                                    = =  ===
     In the evening
     The rice leaves in the garden
     Rustle in the autumn wind
     That blows through my reed hut.
            -- Minamoto no Tsunenobu

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