Table of contents
6.The magnetic fields sensors
7.The inclination measurement system
9.The data acquisition system
11.The power supply
12.Realisation of the PCB
13.The embedded system
14.Static Library Util.a
17.Sensors controller commands
This feature was one of the first parts
we designed. It makes easier the dimensioning of the others components.
The microcontroller ATMEGA32 is sufficient for our application. It includes height
10-bits ADC that is not sufficient to measure the angular rate, the magnetic
field or the acceleration but enough to control the temperature or the voltage.
Therefore we decided to use serial ADC 12-bits (MAX186AEPA). After a
calculation of the sensors resolution, it shows that 12 bits is enough. With a
14-bit application, we will not obtain a better signal than the actual ADC; we
just collect a more great quantity of noise.
On the Max186, 1LSB = 4,096/212 =
On the Atmega32, 1LSB = 4mV
The input signal on the ADC is comprised
just between 0 and 4,096V. Consequently, all the signals have to be centred on
The eight input channels of the ADC are
divided as follow:
-2 channels for the
accelerometer (one for each axis)
-3 channels for the
magneto-sensors (one for each axis)
-1 channel for the gyro.
We have still two channels free. They
will be used to supervise the reference voltage and the inner temperature of
Note: A problem with the microcontroller
is that it is not design to operate outdoors (it doesn’t work when the
temperature below 0°C).