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Minimum sensor recognition distance:
> Sensor’s minimum-distance does not have to be much smaller than 20cm (8“).
Infrared:
- Binary Output: detects whether an object is within a threshold distance
- Multiple Bit Output: detects the more or less accurate distance to an object
Pro:
- Quality products comparatively cheap
- In some cases very high resolution (up to 1 mm)
Contra:
- Problems with sun light
- Problems with recognition of dark or black objects
- Small range sizes
Recommendation after some research:
Sharp GP2Y 0A02 (ca. $11, 20cm – 150cm Range, Analogue Output)
http://acroname.com/products/SHARP-GP2Y0A02YK0F-IR-PACKAGE
(see also: http://acroname.com/articles/sharp-infrared-ranger-comparison for comparison)
Ultrasonic
Pro:
- Not depending on optical properties of an object -> more reliable in common usage
- Larger range sizes
Contra:
- Usually higher prize
- Lower resolution (2-3 cm)
- Problems detecting acoustic quieting objects
Recommendation after some research:
Parallax PING Ultrasonic Sensor (ca. $29, 2cm – 300cm Range)
https://www.parallax.com/product/28015
(maybe cheap replacement: http://www.dx.com/p/hc-sr04-ultrasonic-sensor-distance-measuring-module-133696?Utm_rid=37202148&Utm_source=affiliate#.VTsyqa3tmko)
Radio Telemetry Kit
FPV 433Mhz Radio Telemetry Kit 100mW V1.1:
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