Development of automated weather Station: three cup anemometer and tipping bucket rain gauge

Abstract

Weather is the state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc. Weather measurement tools are used to determine the actual weather and forecasting. Natural wind in the open air is a three-dimensional vector that has the directions of north, south, east and west in addition to vertical components and magnitude (i.e., wind speed). As the vertical component is ignored for most operational meteorological purposes, surface wind is practically considered as a two-dimensional vector. An anemometer or wind meter is a device used for measuring wind speed, and is a common weather station instrument. The rain gauge is an instrument that is used to measure the quantity of rainfall or precipitation over a particular time period at a specific region. The forms of precipitation may be in the liquid form that is the rainwater or the solid forms that are the sleet, hail, or even snow. In Sri Lanka it is as rainwater. In this work we have developed an automated weather station of three cup anemometer to measure wind speed and tipping bucket rain gauge to measure rainfall rate. The current wind speed and the rainfall of the past 24 hours were displayed in a LCD panel where the user can easily read and record the data.

Methodology

A fix magnet is attached onto the three cup anemometer. When the wind blows, cups and axel attached to then will spin relative with the wind speed, thus the magnet will trigger the Hall Effect sensor. A pulse will be generated as an output for each revolution. The time difference from each pulse (length of the pulse) is used to calculate the speed of the wind. The output from Hall Effect sensor will be transmitted to microcontroller to be processed and calculated. The calculated measurements are displayed on the LCD. It is displayed the length of the pulse in milliseconds. A prototype of three cup anemometer was made using Iron Shaft, 2 bearings, 3 Light weight metal rods, 3 cups and, piece of wood (Figure 01). A Hall Effect Sensor and a magnet fixed to the iron shaft were used to detect number of rotations. Electric signal produce due to the Hall Effect is fed to the 16F877A pic microcontroller. A prototype of tipping bucket rain gauge was built by using plastic jar, funnel and plastic, light weight bucket. A light weight ice cream cup was used to build the bucket which contains two separate parts inside the bucket to fill the water one after another and the tipping bucket was set to the lid of the plastic jar with two aluminium L shape pieces (Figure 02). Small magnet was placed at upper edge of the triangle in one side of the bucket. To count the toggling of the bucket, a normally opened reed switch was used and it was placed in one bucket side which has fixed the magnet and covers it with plastic cover to protect from water. Toggling of the bucket was counted by the reed switch.