5. Anemometer

The three-cup anemometer measures wind speed using a Hall effect sensor (SS451A) that detects rotations. Two magnets on the anemometer generate 2 interrupts per revolution, enabling precise tracking of rotational speed. Wind speed is sampled every second by recording interrupt counts and millisecond durations. These 1-second samples are converted into instantaneous wind speeds using the anemometer’s calibration factor. Observations are logged every minute, with:

• Wind Speed: Average of 60 consecutive 1-second samples.

• Wind Gust: Highest 3-second average (three consecutive samples).

Wind speed is calculated using:

$$\text{Speed (m/s)} = \left( \frac{\frac{\text{interrupts}}{2} \cdot 2\pi \cdot \text{radius}}{\text{time (s)}} \right) \cdot \text{calibration factor}$$

• Radius: 0.079 meters (distance from center to cup)

• Calibration factor: 2.64 (empirically determined from wind tunnel testing)

Tutorial Videos

This video playlist demonstrates the entire assembly of the Anemometer. It demonstrates the glue in version of the bearing housing and hub using Qwiic cables. Please follow the manual instructions if using the twist version of the bearing housing or M5 stack Grove cables.

You can toggle between videos using the list icon at the top right or by using the "fast forward" button at the bottom left.

Instruction Slides

Anemometer Tips and Tricks

This document is slightly outdated due to the new threaded/twist version of the hub but still has helpful tips and tricks.

332KB

Anemometer Assembly Hints and Tips.pdf

pdf