Nesbit Solution (Really)

[Wrenow]

The Nesbit problem has finally been solved by a British company <A href='http://loc8tor.com/' Target=_Blank>External Web Link</a>. This locator system uses 2.4Ghz RFID beacons and gives you range and direction on the cellphone sized locator, and also can be set to give an alarm when the RFID tag goes astray (beyound one of 3 preset ranges). Up to 600' range and tracks to within 1&quot;. Available in the US now for about USD$99.

Now, if it can be hacked for interface to the Picaxe as a datalogger or other purposes, this might be a really nice gadget with lots of possibilities. Assuming you can have 2 locators per tag (not necessarily correct), you could do triangulation. However, if you have range and direction, that is not really needed, is it?

It would also make a nice addition to the ultimate fire control system for R/C Model Warship Combat, or for an automated convoy system (where you need to determine the position of the convoy ships relative to each other).

Track control system for R/C cars?

Lots of possibilities.

Now Nesbit's owner will be able to sleep better at night, knowing Nesbit hasn't escaped or been nicked. And can find the little dear under the bushes. ;-)

I found the advert for this device in X-tremegeek, and the lights just went on.

Wreno

 

[demonicpicaxeguy]

thats brilliant although why not just try the same thing with some el cheapo 433mhz modules

 

[Dippy]

I suppose you could make a big one Demon.
But, just for a moment, have you considered the reasons for going to a much higher frequency than 433/434?

Cost? One receiver with LCD and 2 mini tags all for 50 quid - do you reckon you can make a similar setup for less?

 

[hippy]

Ranging and going-out-of-range detection should be fairly easy; signal strength measurements of an incoming ID packet I imagine.

From the advert though I couldn't work out how it does the direction finding.

My guess would be omni-direction aerials and the relative signal strength of an ID packet on each determines if it is straight ahead or to the left or right. A single aerial rotated by a servo could scan radar-like.

If there's only a single fixed aerial I'm intrigued as to how direction can be determined without manual intervention such as scanning in an arc to find what one is looking for.

 

[moxhamj]

It is a bit hard to guess the scale from the photos, but maybe they are hiding a small yagi or even just a dipole in the case?

 

[Michael 2727]

At 2.4 G it probably uses TDR or similar to
detect the signal speed/distance=length.

 

[demonicpicaxeguy]

i imagine you probably just move the thing left to right you're self which is what i'm thinking about for the 433mhz modules
<A href='http://www.jaycar.com.au/productView.asp?ID=ZW3100&amp;CATID=&amp;keywords=433&amp;SPECIAL=&amp;form=KEYWORD&amp;ProdCodeOnly=&amp;Keyword1=&amp;Keyword2=&amp;pageNumber=&amp;priceMin=&amp;priceMax=&amp;SUBCATID=' Target=_Blank>External Web Link</a>

one of these attached to nesbit with a 18x and a battery
transmitting a fixed message like a beacon

then with your matching reciever and a directional antenna you're in buisness
just move it around until you recieve the message... you get the general idea
and if you want to have a second one

 

[BrendanP]

Ive done a bit with video tx at 2.4ghz. I got modules in from TW that TX'D 100 milliwatts. The usual signal strenght limit here in Aus. is 10 milliwatts. Id say its the same in the UK. Even with 100 milliwatts with hi gain directional antennas at 2.4ghz the signal is OK in clear line of site. However plant foliage, light rain etc.in the way will cause problems. Forget about buildings, fences etc. At 10 milliwats I suspect you would have no hope of finding little johnny or Nesbit if he's in scrub or even just long grass.

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Edited by - BrendanP on 14/06/2007 00:48:19

 

[sedeap]

**********
Nice gizmo...
i try to get one to learn *how to's*

)

 

[c6jones720]

I just saw a video of the device being used. It has an audio output and basically outputs tones depending on the proximity of the object to be detected.

It looks like the device would have to manually set up to start off with but thereafter decoding the tones to locate the object is almost certainly possible with a picaxe.

 

[c6jones720]

I asked them, and they told me that ther will be computer interface to this in 2008-2009 its been delayed. I would have thought it was a pretty obvious thing to add an I/O port to this device. When the interface comes out this will potentially have huge implications for robotics and other embedded location applications.