[Robotgroup] Triangulation

[Clendon Gibson]

The problem with RF triangulation in enclosed spaces is reflection. The RF you are most likely going to produce will bounce off the metals and other hard things in the environment.

This can make accurate triangulation tricky.

Personally I would not bother with building transmitters. There are already dozens of transmitters near you. Just tune around your AM or FM dial. (Pick FM stations. The amplitude won't vary with the music they are playing, just the distance from you.) Of course you have to look up where these transmitters are, but I bet that stuff is on the internet. Because they will have different signal strengths there will be calibration involved, but you have a PC at your disposal so...

When you have your frequencies picked out you want to create turned filters attached to antennas. The filters are simple narrow band jobs tuned to the stations of your choice. Run the other end of this to a ac to dc rectifier. (Small transformer and some diodes depending if you want full wave or half wave.) Hey presto you have a RF amplitude to DC Voltage converter. DON"T just plug this into a ADC. You are not likely to get enough sensitivity. Instead use the voltage to run a 555 timer where the voltage changes either the pulse length or the number of pulses per second. Your PC can count very fast after all.

----- Original Message ----
From: Robo Al <sp-18561884 at ggsys.net>
To: Austin Robotgroup Mailing List <robotgroup at puremagic.com>
Sent: Friday, February 1, 2008 4:20:36 PM
Subject: [Robotgroup] Triangulation


Does 
anybody 
know 
any 
links 
or 
reference 
material
about 
non 
GPS 
triangulation?

I 
would 
like 
to 
play 
with 
something 
within 
these
requirements:

* 
open 
and 
closed 
spaces 
around 
150'x100' 
max 
size 
(ie.
  
a 
yard 
or 
inside 
a 
house)
* 
accurate 
to 
within 
1 
to 
3 
centimeters
* 
inexpensive. 
Hopefully 
sub 
$40 
for 
parts.
* 
A 
computer 
or 
fast 
uC 
will 
be 
available 
to 
do 
the
  
calculations 
so 
the 
$40 
is 
just 
for 
sensors 
and 
I/O
  
interfacing 
to 
the 
computer.

I 
would 
imagine 
setting 
3 
or 
4 
radio 
beacons 
within 
my
fence 
posts, 
but 
I'm 
afraid 
I 
just 
don't 
know 
enough
about 
radio 
triangulation.

Thanks,

Alberto


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