Think & Create

Bluetooth tracker

by on Jan.27, 2012, under My gadgets

This is a position tracking system. This system communicates with people’s electronic devices via Bluetooth protocol. Then visualize people’s location on screen in real time.

There are a few reasons why I choose Bluetooth. People do not need to bring anything beside their daily-carried cell phone and laptop. Since Bluetooth needs a bi-direction commutation between the sensor and devices, people have much more control of their privacy than passive listing techniques. If people feel uncomfortable about this project, they can simply turn off discoverable function on their device or turn of Bluetooth completely. Each Bluetooth device has a unique MAC address so different devices can be distinguished by their address.

This system includes a computer with a USB adapter and Bluetooth sensors. The sensors are connected by 2-pair CAT3 cable. One pair is used for power and another for RS-485 One pair is used for power and another for RS-485 communication. All nodes are connected in parallel so the scale of this system can be changed easily. All nodes are controlled by computer and send information gathered back to computer. The computer analyzes all information, calculate device’s position and visualize them.

Instead of using the triangulation methods to get the accurate position of a device, this system only determine which room the device is in. This is much easier than the triangulation. Also the accuracy of signal strength (RSSI) is not high enough to make triangulation necessary. So I used a simple algorithm to detect which room the device is in. If all sensors can find the device, the device may be in that room. The device will be classified to the room with the strongest average signal.

In the visualization process, I use different colors to represent different devices to improve its appearance. When a device stays in one room for a long time, the circle will grow up gradually.

 

(A working node)


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