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Electronics

 

Razor IMU

The project specifications require an electronic device that can output data streams with 3-axis data of the acceleration and angular rotation. This is obtained using an Inertial Measurement Unit (IMU). The Razor IMU with 9 degrees of freedom (by Sparkfun) has been chosen for this project and is shown to the right. The specifications of this IMU is are follows:

A 3-axis ±16g capacitive accelerometer, ADXL345 by Analog Devices.

A 3-axis MEMS vibratory gyroscope, ITG-3200 by InvenSense.

A 3-axis anisotropic magneto-resistive magnetometer, HMC5583L by Honeywell.

data_flow.png

As shown in the process flow block diagram above, the data from the sensors is received and processed using an ATmega328 Arduino processor. For the wired solution, the data is then transferred through the FTDI (Future Technology Devices International) interface board which is connected via USB to a PC running the Arduino software. For the wireless solution, the data is transferred through a Bluetooth module, which can then be sent to a Bluetooth capable PC or directly to a smartphone.

The device operates at 3.3VDC, with low power dissipation. For the wired solution, the board is powered through the USB connection. For the wireless solution, a lithium-ion rechargeable battery is used to power the device.

The Razor IMU + FTDI board costs approximately £100. The Razor IMU + Bluetooth module setup costs approximately £120, and all boards are commercially available. The boards for the project have also been modified to optimise space utilisation.