for this test we were interested in the effects of orientation on a second axis. we had one mote (fixed) laying flat, batteries down, with its usb pointed directly at the other mote. .55m away was the other mote, with the circuit board facing the first mote, with its usb facing the ceiling. this mote was rotated in 30 degree increments, such that the usb was always facing the ceiling, but the board rotated to be facing away from the first mote. a constant separation of .55 meters was used, and all possible broadcast strengths were used. rssi data was then recorded to give us an accurate picture of the radiation cloud at .55m in this particular direction of rotation.
the graph below gives rssi readings at power levels 3, 10, and 20 at each of the rotations. NOTE: these readings are only for one distance, at different power levels, not different distances at the same power level.
Nice experiment. If I follow this correctly, I think it means that orientation about the long axis doesn’t matter nearly as much as orientation about the plane of the board. Do you agree?
Comment by gthomas — August 26, 2009 @ 7:44 pm
yes. we are very excited about this aspect.
Comment by E M — August 27, 2009 @ 2:26 pm
Indeed, it validates the concept of using the badges as though orientation didn’t matter. It doesn’t ensure, however, that rssi will indicate distance well–that is up to other experiments, so the validation of the badges would rely on the assumption that the distance effects we measured in some orientations are proportional to the effects of distance in this orientation.
Comment by Gray Thomas — August 28, 2009 @ 2:40 pm