“An anemometer is a device used for measuring wind speed and direction. While there are many different types of anemometers, the most common versions are cup anemometers, vane anemometers, hot wire anemometers, and pitot tube anemometers. This project, based on the vane style, creates a DIY handheld version using readily sourceable electronic components.
This whole project is designed around the average computer cooling fan. Cooling fans typically come in one of three styles, each improving on the controllability of the latter. Two-wire fans are used for the most basic applications. Accommodating only a power and ground connection, these fans will only provide the ability to turn on and off. Three-wire fans add a tachometer output to the original two wires. Typically utilizing a hall effect sensor, this third wire will output a pulse voltage a set amount of times per fan rotation. These pulses can be used to monitor a fan’s condition and detect any failure. The final four-wire option creates the ability to have full control over the fan. A duty cycle can be sent to the fan through this fourth wire to vary the speed of the motor.
For this particular project, the third wire option will be focused on. The pulse output, used for measuring rpm, can be connected to an Arduino to measure the average fan rotations that occur during a set time interval.”