question for expert time guys
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
- base station 1 indicates we are determining position of device A.
- Each base station 1, 2, 3 take turns pinging the device to determine
distance. - A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast - Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results. - obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time
accuracy is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
Also the fixed stations can not have OCXO?
On Fri, Feb 1, 2013 at 5:37 AM, Rick Harold rickharold@gmail.com wrote:
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
1. base station 1 indicates we are determining position of device A.
2. Each base station 1, 2, 3 take turns pinging the device to determine
distance.
3. A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast
4. Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results.
5. obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time
accuracy is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi Rick,
You would do better putting a small GPS receiver in the mobile and transmit with
a 2.4 GHz Blue tooth transmitter. The GPS devices can be gotten very small (your
thumb would just about cover it up). They are also very light and draw very
little power. That would save you two transmitting and receiving stations.
Clearly the software would be infinitely easier as you would not need to deal
with all the timing issues.
GPS would provide the position information and its time count for each report, if
that mattered. Some representative GPS receivers can be research at the
following location:
https://www.sparkfun.com/categories/4
They also have various transmitter devices for blue tooth, WIFI and Zigbee. You
can view these under the following category:
https://www.sparkfun.com/categories/16
This is only one place that provides such things for hobbyist. There are others,
as well as, going direct to the manufacturers for such OEM products.
I do not know if you are aware of it, but and finale product that transmits over
the air may need FCC certification. Other sections might apply in certain
circumstances.
Bill....WB6BNQ
Rick Harold wrote:
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
1. base station 1 indicates we are determining position of device A.
2. Each base station 1, 2, 3 take turns pinging the device to determine
distance.
3. A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast
4. Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results.
5. obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time
accuracy is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi Rick,
You would do better putting a small GPS receiver in the mobile and
transmit with
a 2.4 GHz Blue tooth transmitter. The GPS devices can be gotten very
small (your
thumb would just about cover it up). They are also very light and draw
very
little power. That would save you two transmitting and receiving
stations.
Clearly the software would be infinitely easier as you would not need to
deal
with all the timing issues.
GPS would provide the position information and its time count for each
report, if
that mattered. Some representative GPS receivers can be research at the
following location:
https://www.sparkfun.com/categories/4
They also have various transmitter devices for blue tooth, WIFI and
Zigbee. You
can view these under the following category:
https://www.sparkfun.com/categories/16
This is only one place that provides such things for hobbyist. There
are others,
as well as, going direct to the manufacturers for such OEM products.
I do not know if you are aware of it, but and finale product that
transmits over
the air may need FCC certification. Other sections might apply in
certain
circumstances.
Bill....WB6BNQ
Rick Harold wrote:
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
1. base station 1 indicates we are determining position of device A.
2. Each base station 1, 2, 3 take turns pinging the device to determine
distance.
3. A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast
4. Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results.
5. obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time
accuracy is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Can the base stations be interconnected via cable?
In that case, wouldn't it suffice to have the mobile device send an
unmodulated carrier of low enough frequency, and compare the phase
between the receiving base stations, taking the (known) cable delays
into account?
Cheers
Stefan
Rick Harold wrote:
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
1. base station 1 indicates we are determining position of device A.
2. Each base station 1, 2, 3 take turns pinging the device to determine
distance.
3. A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast
4. Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results.
5. obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time
accuracy is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 1/31/13 8:37 PM, Rick Harold wrote:
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3
fixed positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
Don't do "pinging" and time of flight. Do phase measurements. At 900
MHz the wavelength is 33cm. Essentially rather than trying to ping,
you're measuring the positions of multiple zero crossings averaged over
some amount of time.
Can your "base stations" be interconnected so they can share a common
reference signal?
What position accuracy do you need? How big an area?
Can you initialize at a known position and then track, or do you need to
come up cold?
There's a lot of clever schemes that use multiple frequencies from a
common source to disambiguate phase: e.g. if I measure phase at 908 MHz
and phase at 928 MHz, I can effectively also measure phase as if I were
radiating at 20 MHz, so that gives me coarse position (out of 15m
wavelength) and fine position (out of 33cm wavelength)
Just to make sure I understand the 'ground rules', the three base stations
define a plane, unless they are on the same line. Is the mobile device also
in this plane? How far apart are the base stations relative to the location
of the mobile device? Or, better, is the mobile device 'inside' this
triangle or 'outside'?
How precisely can you know the location of the base stations without
violating the 'inexpensive' rule? Can the base stations 'ping' each other?
Seems to me that an accuracy to 3 feet is going to be a problem without
precise time measurement unless you can use some 'known' reference (like the
precise location of the base stations) and the ability to use that 'known'
to 'calibrate' each measurement, thus minimizing the errors from 'drift',
etc., in the available, 'inexpensive', time references.
Good luck.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Rick Harold
Sent: Thursday, January 31, 2013 10:37 PM
To: time-nuts@febo.com
Subject: [time-nuts] question for expert time guys
To time experts/EE's.
I would like to triangulate a position of a device which moves using 3 fixed
positions devices of known location.
The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
appropriate frequency.
These two type of devices (fixed and mobile) are all under my control and
thus customized as needed.
The mobile device (not a phone, custom device) would be the least expensive
item. I'd like a range of 150 feet or better and accuracy of 3 feet or
better.
When manufactured these items they can be calibrated in order to adjust for
any variation in IC's, discrete components etc...
We can assume for now the temperature is constant 70 degree temperature.
Cost is the key design factor.
The general flow is:
- base station 1 indicates we are determining position of device A.
- Each base station 1, 2, 3 take turns pinging the device to determine
distance. - A ping consists of (something like, e.g. frequencies as examples)
-send 915mhz signal from base station to device
-device response ASAP on different frequency
-station waits and counts 'time' for return
-this is repeated N? times to get best avg/accuracy.
-The mobile device does not move very fast - Since delays of the process on each unit is calibrated the device and
base station would subtrack that time out from the results. - obviously with 3 distances we can determine the 2D position of the
mobile device
I know the time accuracy is the key to count time = feet, 1ns. This
overall project is not new concept. How to make it "inexpensive" is key.
how inexpensive, very ;-) no OCXO or expensive components like that.
That's my goal, and I'm looking for help on the design/thought process of
getting there.
I am open to a consulting arrangement for a fee, please email if you like.
I've worked with 'regular' EE's (I'm a software guy) but this time accuracy
is too much for them.
Esp. finding a way to do it inexpensively.
Thanks for any thoughts.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.