Re: Relative Positioning

On May 5, 1:17 pm, mattrapop...@xxxxxxxxx wrote:
I have a person and I want to place small transceivers in various
places on his body.  The transceivers would all be able to detect
their distances from each other using some sort of wireless

The "time of flight" for wireless, as you propose, is going to be very
difficult because electro-magenetic waves (speed of light) are
extremely fast. So, I woudl abandon that idea. But, sound is an
alternative. If each transceiver takes turns emitting an ultrasonic
"ping", then each of the other transceivers can record the time it
takes for the sound to travel to them. But, you also need to let each
transciever know when the pulse was emitted by either a wired or
wireless transmission (an IR beacon is common, but you may not have
line-of sight to do this)

Here is one link to the type of system I am describing, as commonly
used in robotics;
http://www.restena.lu/convict/Jeunes/beacon.htm

In your case, you might send an IR signal (similar to those used in a
TV remote control) to tell a particular beacon to "Ping"... at the
same time the other transcievers read the IR signal to know which
transciever is doing the Ping and start to listen for it.

But, in the above method, you might have issues with some transcievers
not getting the IR signal. But, if you are in a small-ish room, you
can just flood the room with the IR, and it may work. Still, a wired
system is going to be a lot easier to do.

Joe Dunfee
.

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