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I would like to have two HC-05 Bluetooth modules attached to my Arduino MEGA, both calculating the Bluetooth signal strength, emitted from my phone, to determine whether the phone is located in front of the board (both signals are relatively equal), to the left of the board (the left Bluetooth module picks up a higher magnitude signal than the right) or to the right of the board (the right Bluetooth module picks up a higher magnitude signal than the left).

  1. Is there a way to connect two bluetooth modules to one arduino simply to compare bluetooth signal strength?

  2. How do I program my already connected bluetooth module to detect signal strength?

  3. If 1) is not feasible, can you suggest me any alternative to determine the position of my phone (avoiding GPS modules)?

closed as too broad by per1234, sempaiscuba, gre_gor, VE7JRO, MatsK Jan 8 at 14:50

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I checked several HC-05/06 datasheets looking for any that had a command to read its signal strength, but didn't find any.

My suggestion would be to test the device for any inherent directionality and take advantage of that (much like the old low-frequency RF direction-finding loops; turn the loop until the signal goes away - nulls out - then the signal originates on a line perpendicular to the plane of the loop). The Bluetooth board's antenna won't be that dramatically directional - it's design goal was to be omni-directional; just what you don't want for this application.

You might try putting a foil cone around the antenna-end of the HC-05 to try to give it some directional sensitivity. If your module is thermo-wrapped in plastic, as mine is, this should be easy without shorting out something on the board.

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The goal is to be able to sweep around the room to whichever direction you lose/find the signal. Then the board will be pointing toward your phone. It may have a pretty wide capture cone so you might need to find the left and right edges of the cone and mentally split the difference.

Once you have two lines of direction from different places, your phone should be where they intersect. But again, those "lines" may (will) be rather broad anglular areas, so the intersection will be the diamond-shaped area, not a point, where those angular areas overlap. And all of this assumes you can make your board directional enough to narrow your search space enough to eventually close in on your phone in a few tries.

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I suggest you to consider Bluetooth Low Energy Beacon technology.

Beacon data has special field that can be used to estimate the distance. So, BLE Beacon is used in indoor positioning application.

There are two roles in BLE Beacon:

  • Observer: who listen beacon data.
  • Broadcaster: who send beacon data.

You can use two bluetooth module attached to an Arduino mega that act as Observers and the phone act as Broadcaster of beacon data.

A problem is that HC-05 is a classic bluetooth and not BLE 4.0. You have to choose another bluetooth module, like for example an HM-10.

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