Table of Contents
Advertisement
Philips Semiconductors
Electronic Compass Design using
KMZ51 and KMZ52
6. DIRECTION DETERMINATION UNIT (DDU)
6.1 8-Segment Compass
If applications require a rough direction indication only, then a compass set-up is sufficient, which identifies the
nearest of the eight cardinal or intermediate points (e.g. N, NW, S, SE, ...). This information can be gained from
the SCU outputs without evaluating the arctan function in equation (1). Figure 18 shows the principle. Here the
SCU output signals Vx and Vy are shown for a full clockwise rotation of the compass. By comparing the SCU
signals with the thresholds Vt+ and Vt-, logic signals N', S', E', W' can be derived, which contain the desired
information. Vt+ and Vt- are equal to +/-sin(22.5°). Figure 19 shows a circuit for the direction determination. As a
display, e.g. LEDs can be driven by the respective outputs.
SCU Signals
100%
N'
Vt+ = 38.3%
Vx
Vref
Vy
Vt- = -38.3%
E'
-100%
N
NE
Figure 18
Direction determination for 8-segment compass
Vx
+
o
Vt+
-
Vt-
+
o
-
+
o
Vt+
-
Vt-
+
o
Vy
-
Figure 19
Circuit for 8-segment compass
W'
N'
180
360
S'
E
SE
S
SW
W
NW
N
MLC760_1
N´
S´
W´
E´
25
Application Note
AN00022
N
NE
E
SE
S
SW
W
NW
Advertisement
Table of Contents
