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Mecahnical Assembly •
GPS - Digital
Compass •
Proportional Servo •
Circuit Description •
Software •
Test Modes •
Crossing the Atlantic •
Sources
Digital
Compass
The
Roboat uses a digital compass sensor analog model
6100 (distributed by Pewatron) to determine which
direction the Roboat is heading (azimuth). This sensor
has the shape of a small cylinder that is 15 mm high
and 13 mm in diameter, and contains a tiny magnet
and two Hall-effect sensors. The magnet is free to
rotate around its vertical axis and point north under
the influence of the earth’s magnetic field.
The
two Hall-effect sensors are mounted around the tiny
magnet, 90° apart from each other. When the magnet
rotates, the outputs of the two sensors describe the
sine and cosine curves that, using a power supply
of 5 V, have an average value of 2.5 V and range between
1.8 and 3.2 V.
The
Roboat azimuth (degreed) can then be computed as the
ArcTangent of the ratio of the displacements of the
two curves from the average (see
Figure 4).
