The Acceleration Sensing Glove (ASG) is composed of 6 Analog Devices ADXL202 accelerometers and an Atmel AVR AT90LS8535 8-bit microcontroller.  All processing is currently performed on the host computer, wired via COM port.

Current power consumption of accelerometers and microcontroller:

6 * (0.6mA * 3.3V for ADXL) + (6.4mA * 3.3V for Atmel) = 11.9mW + 21.1mW = 33mW

This implementation assumes continuous operation of the accelerometers.  The Atmel AVR microcontroller is used to sample and perform an A/D conversion from all the accelerometers.  However, the ADXL202 has digital outputs, where the duty cycles are proportional to the acceleration on an axis, that eliminates the need for an A/D.  Also, they can be power cycled for better power efficiency.  We can use a TI MSP430C311 microcontroller (used in the Milk Sensor writeup) to decode the duty cycle output for each accelerometer.

The ADXL202 requires 1.6ms for a good reading.  The shortest duty cycle period is 0.5ms.  We need at least two duty cycles to perform a reading from both the X and Y output (see Analog Devices Application Note on decoding).  With the TI running at 1Mhz and with a 6ns wakeup time, it is the accelerometer times that are the predominant factor.  At a 30hz sampling rate (say, for motion capture animation), the active power consumption for a mote with these components would be:

(1.6ms + 2 * 0.5ms) * 30 samples/s * (0.6mA + 0.4mA) * 3V = 234uW

Still not in SmartDust range (especially after adding idle and communication consumption), but getting closer.

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