FIGURE 2: CIRCUIT DIAGRAM FOR THE MASTER.
slave nodes are strapped onto the anatomy, and the accelerations imposed upon the slave nodes as they piggyback
during body movements are measured to calculate the gait.
The key sensor component residing in every slave node
of our current gait detection system is the humble triple
axis MEMS-based accelerometer ADX330. In lieu of the
stand-alone accelerometer chip, we chose to use the
DE-ACCM3D modules from Dimension Engineering
( www.dimensionengineering.com) as they carry
on-board regulators, power filters, reverse voltage
protection, and provide buffered outputs.
The three analog outputs (one for every axis) from the
DE-ACCM3D module in each slave is then fed into programmable gain amplifier modules within a Cypress C8YC29466
PSoC mixed signal array microcontroller. The amplified
signals are then digitized using an incremental ADC converter
(TRIADC8) capable of fast conversions. Note that the
TRIADC8 was chosen for this project solely for superior
speed. However, the PSoC provides a large variety of
incremental and delta-sigma converters that can be
FIGURE 3: PHOTOGRAPH OF THE COMPLETED SLAVE MODULE.
SERVO 12.2008 39