Author Topic: The opposite everyone is trying to achieve... low distance transmit power  (Read 3306 times)

DeltaZuluCharlie

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #15 on: December 23, 2016, 01:04:30 PM »
I humbly suggest that you look at iBeacons again to see how they work and what their purpose is... (hint: A SmartPhone or Tablet IS a BLE Host with respect to iBeacons)

Tom

I have indeed looked into it further. It seems the prices have come down tremendously since I first looked at BLE transceivers a couple of years ago along with a lot of DIY/open source community development.

My concern at the time, and up to you suggesting I take another look was that I didn't want the iBeacons on walls and having to carry around a smart phone all the time. I wanted the opposite but without expensive iPhones or whatever on the wall.

Looking at the nRF51822 right now for the room sensors and still poking around for 'fobs'. TI has some interesting sensortags.

DeltaZuluCharlie

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #16 on: December 23, 2016, 01:08:49 PM »
Concur with BLE beacons - as used in short distance range finding applications in lots of domains these days ;-) . . .

For example to track people who wear them on a pendant around their necks so that an automated system can detect whether they have stopped moving, or where they are in a building . . . add in a pressure sensor and you can detect whether they have fallen or just stopped moving . . . if they happen to be prone to falling and getting hurt for example . . .

Dang you Ziplockk. Now I have to integrate an accelerometer into my fobs. :P

TomWS

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #17 on: December 23, 2016, 06:56:57 PM »
I have indeed looked into it further. It seems the prices have come down tremendously since I first looked at BLE transceivers a couple of years ago along with a lot of DIY/open source community development.

My concern at the time, and up to you suggesting I take another look was that I didn't want the iBeacons on walls and having to carry around a smart phone all the time. I wanted the opposite but without expensive iPhones or whatever on the wall.

Looking at the nRF51822 right now for the room sensors and still poking around for 'fobs'. TI has some interesting sensortags.
The model I'm suggesting is to use an off-the-shelf fob/tag, similar to what @ziplockk mentioned, as the key chain/fob/bodypiercing/whatever that gets carried around.  These all send periodic beacons.

At each point where you care about detecting the presence a 'body' carrying such a beacon, you have a 'station' that consists of a BLE host/client/whatever term du jour is being used (BlueGiga has a couple of usable ones) that, in turn, is connected to a gateway device (ESP8266 is a reasonable choice, but RaspPI, or any other programmable device that can bridge between the BLE world and a LAN will work), which revolves the closeness of the 'presence', possibly comparing with other stations, to determine where, exactly the 'body' is with respect to the stations.  The concept is trivial and workable as long as you're prepared to fill in a LOT of gaps in coding/hardware integration.  I'm not aware of any affordable off the shelf solutions.

Tom

WhiteHare

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #18 on: December 24, 2016, 06:14:03 PM »
Perhaps using the "Tile Mate" approach would be easier?  Just make the receiver beep audibly, and then let your ears guide you to it.

Felix

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #19 on: January 01, 2017, 04:56:22 PM »
FWIW I ran across this article where the author (good credentials) says:

Quote
Triangulation on BLE is impossible because on 2400 MHz you will have a lot of reflections, multipath plus phase shift.
Further down:
Quote
A detection on room level is possible. If you add Kalman filters and some more sources like the magnetic field of the earth, accelerometers or even ultrasonic sound then the result will be much better than on BLE beacons only.

Maybe worth a read.

DeltaZuluCharlie

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Re: The opposite everyone is trying to achieve... low distance transmit power
« Reply #20 on: January 01, 2017, 04:59:24 PM »
Thanks. I've also been reviewing this one over the holidays: http://www.cl.cam.ac.uk/~rmf25/papers/BLE.pdf