How to find distance between two WSN nodes (for nRF24L01)

[hikaan]

Hi

I am using nrf24L01 transceiver in my WSN node. In this transceiver there is no support for RSSI. In this case, is there any method to find the distance between two WSN nodes ? Is there any scheme like TOF (Time of Flight) that will be useful or not ? Pls suggest your opinion.

Thanks
G Kannan

[temtronic]

You probably will not get any responses with a solution( there are 3 that I know) unless you report which PIC type and compiler version you are using as well as application(home,office, school), accuracy of distance( 1ft, 1mm, ??),update rate(1 hr, 1 sec,1ms,??).

[Eduardo__]

Dear folks. I´m looking for the same solution. Do you know whether is possible to do this with RF? like an LPS(Local positioning system)?

My needs are:
application(home or school), accuracy of distance(1inch or less),update rate(100ms or better).

I was looking on ultrasound solutions as I cannot think nothing faster enough for reading a RF signal time of flight(should be faster enough for read differences of pico-seconds). Even GPS system uses atomic clocks and it have meters of precision.

Anyone have ideas?

Thanks a lot!!!!
_________________
Eduardo Guilherme Brandt

[temtronic]

Several solutions all based upon specs and money you can afford for the project.
How much money will you spend ?
Simple GPS can give you 1" resolution at 1/10th second update rate.

[Eduardo__]

But, how to achieve GPS 1" resolution?


Of course, despite of how much money we have, I would like to know your ideas, if possible.
Every solution must be as cheap as possible, but I know it´s not possible.

I cannot understand how GPS receivers can manage so tinny time differences. I know that pico or even nano-second times are problematic for uCs and even uPs. Do you know how this works on this problem?
_________________
Eduardo Guilherme Brandt

[temtronic]

The basic solution involves using multiple GPS units per 'device'. Using 8 it is easy to get 1" resolution.
It's up to you to buy 8 identical GPSes,get all 8 talking to one PIC (faster is better) and do the code to figure out exactly where the device is.

It's not really 'rocket science' just looking at the problem from another 'angle'. When access to milsat gpses was blocked, using comsat gpses required 'outside the box' thinking.

You haven't given details as to the area or range the device has to be found in (room, house, 5 acres, 100 acres), line of sight or rough terrain, weather conditions, speed of target, etc. All are factors in a project like this.

If this is to be in say a 20 x 20' room, one level, simple LADAR will work, easily <1"

[Eduardo__]

Dear Mr. Temtronic.
Thanks for sharing with us.

It´s a good Idea to buy 8 gps(it´s not expensive, U$30,00 each). But I not understood the principle of operation. Each of 8 gps will give me an approximation. What to do with each gps data(Latitude, longitude, height)? Make an average?

I´ve heard about DGPS system. DO you know how it exactly works?

About LADAR, are you talking of lasers?
_________________
Eduardo Guilherme Brandt

[Eduardo__]

If I understood, LADAR seems to be a better system to see depth. To build a 3D from images.
_________________
Eduardo Guilherme Brandt

[Eduardo__]

[temtronic]

MILSAT ( aka military GPS satellites)
COMSAT (aka commercial GPS satellites).

[Eduardo__]

[SherpaDoug]