Part of Research Notes of Kristof Van Laerhoven. Last update: Monday, 24 May 2004 14:46:42 +0100

The 'Porcupine'

The Porcupine is a microcontroller-based unit that contains 9 ball switches, and is intended to be part of a network of others for position- and motion detection. Its name was given by a BT researcher at the Wearable and Implantable Body Sensor Workshop in Imperial College, London in early April. 

The first versions use a Smart-It prototyping board as a core component, and have an experimental add-on board that contain the ball switches and their resistors. Below are a few pictures of one of the very first Porcupines (click on the thumbnails to see the large version):

The module just underneath the add-on board marked 'BIM2' is an RF transceiver that forwards the data at approximately 70 Hz to a base station where the data can be processed. The output bits are encoded in twos complement to avoid any problems with the wireless transfer (an imbalanced bitstream can lead to errors). To preserve battery power, RF transmission will only occur if activity is detected trough the ball switches.

Building a Porcupine should be straightforward, as it consists mainly out of a common mini-DIY Smart-It (schematics, PCB layout top and bottom, step-by-step building instructions) and a prototype board with 9 ball switches and resistors.

Experimenting with the Porcupines. Below are some action shots of experiments where we attached 10 Porcupines to a person's leg (thanks Dave). The data was wirelessly transmitted to a base station which could theoretically be 300 metres away, but I followed the test subject closely with the base station (attached to the laptop) to make sure that the transmission would go smoothly:

And here is one of the nicely annotated plots that was (manually) created after the data logging (for 1 Porcupine, so just 1/10th of the sensor data):

Last updated by Kristof Van Laerhoven, 24/05/2004 14:46:42 +0100