Data Sheet

Marker Detection
MGSWxxxx Magnetic Sensor Datasheet 8
Marker Detection
Markers are pieces of magnetic tape that are affixed on the left and/or right side of the main track. To differenti-
ate them from the track, markers have opposite magnetic polarities. These markers can be used to inform the
robot of special areas along the track, such as forks or merges ahead, high or low speed zones, charge stations,
etc. Markers must be positioned 15 to 30mm away from the edge of the main track for proper operation, as
shown in Figure 6, below:
South
Sensor
North
15-30mm
North
Main TrackLeft Marker Right Marker
Simple Left Marker Simple Right Marker 2 Dimensional Markers
FIGURE 6. Direction Markers
The Figure 7, below, shows an example of a simple marker (i.e. marker present or absent) and two dimension-
al markers where a pattern is used to encode more complex information. In this example, using the built in
scripting language, the sensor can be made to count the number of right markers while a left marker is pres-
ent.
South
Sensor
North
15-30mm
North
Main TrackLeft Marker Right Marker
Simple Left Marker Simple Right Marker
2 Dimensional Markers
FIGURE 7. Marker Usage Examples
Absolute with Markers Detection Mode
The sensor has two modes of operation. In Absolute mode, the field is measured relative to a reference ambi-
ent 0 level, a shown in Figure 8, below. A little above this level, the signal will be considered as being from the
Track. At three user selectable sensitivity levels below the zero line, the signal will be considered as a Marker.
Track
High
Medium
Marker Detection
Sensitivity
Low
Marker
Ze
ro Level
Track Detection Threshold
}
FIGURE 8. Detection Levels in Absolute Mode