Archive for the ‘transciever’ Category

The Sociable Pint at Allen Street Hardware - 11/30/09

Documentation from the November 30th show at Allen Street Hardware, Buffalo, NY.

The Sociable Pint - 11/30/2009 - Allen Street Hardware Cafe from muse207 on Vimeo.

BREAKTHROUGH!!

MESH NETWORK IS NOW FUNCTIONAL!!

ALL MODULES CAN COMMUNICATE WITH ANY OTHER MODULE WITHIN SIGNAL RANGE!!

RSSI IS WORKING IN ALL MODULES TO REVEAL (approximate) PROXIMITY OF CLOSEST MODULE!!

YAY!!

(finally)

(onto the next problem)

Xbee Modules as Proximity Sensors

For this project I want to use the Xbee modules, not only to allow the glasses to share data with each other, but also as proximity sensors. To test whether that this is a viable option, I placed two Xbee modules at specific distances from each other and took signal strength measurements over a minute. I averaged these values and graphed them.

One module was connected via USB to a computer so I could collect the antenna strength data directly to the computer. I wrote a short python program to assist me in the collection of this data.
Signal Strength of Xbee modules
According to this investigation, I am a little worried about using the Xbees to determine proximity. I tested the Xbee modules in an open space in a clear line of sight from each other and the signal strength values were very inconsistent. A bar situation will be much more complex because the space will contain obstructions such as people and walls. Additionally, I did not test the Xbee modules within the glasses. I plan to include capacitance sensors within these glasses which means that the glasses will be covered with a clear conductive film. The problem with this strategy, even if it works well with the capacitance sensors, is that the film may dampen the signals sent between the glasses.

In a perfect world, it is my hope to eventually find a way to accurately measure distance between glasses so I can use triangulation to map out the location and movement of the glasses within the bar space. Currently, I can tell whether two glasses are within 5 feet of each other through signal strength. At the moment I plan to integrate close proximity events like this into my project.

I have not found a way to determine signal strength between the modules without putting the Xbees into command mode. This is incredibly undesirable because I want to be constantly collecting and sharing accelerometer data and I can not do this when the Xbee is in command mode.