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CHAPTER 4 ■ SENSORS 129

4.3 Distance Sensors (IR and Sonar)

Distance sensors help your robot navigate and keep from hitting things. Here, I’ll discuss two
types of range finders: infrared (IR) and sonar. Use Table 4-1 to best identify what sensor you need.

Table 4-1. Sensor Ranges
Sensor Range Divergence Best Use
Bump Switch Few inches n/a Fast, fail-safe sensor.
Proximity Switch Less than 1 foot 20 degrees from center Proximity for stairs,
blind spots.
IR Sensor 4 inches to 31.5 inches 15 degrees from center Movement in tight
quarters where sonar
might give false reading.
Devantech SRF04 4 inches to 9 feet 22.5 degrees from center Obstacle detection.
6500 Sonar 4 inches to 35 feet 15 degrees from center Large distance ranger with
narrow beam width. Good
for localization and map
building.

The first sensor with the shortest range is the Sharp Infrared GP2D02 distance sensor (see
Figure 4-14). It has a range from 4 to 30 inches and costs about $12.

Figure 4-14. The Sharp Infrared GP2D02

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