domingo, 15 de março de 2009

An ethernet weather station

Usando um ‘add-on’ para o já existente servidor AVR Ethernet, vamos construir uma estação meteorológica. Isto é: Uma estação meteorológica com um servidor Web integrado. Os artigos relacionados que descrevem como construir o servidor Web AVR estão aqui:
  1. An AVR microcontroller based Ethernet device
  2. HTTP/TCP with an atmega88 microcontroller (AVR web server)
Os componentes para a construção desta estação meteorológica podem ser encomendados a partir de·
O sistema é modular. Você pode construir uma estação meteorológica Ethenet pura ou uma estação meteorológica Ethenet com um display LCD adicional.



My original plan was to have sensors for temperature, air pressure and wind. I started a prototype and it worked very well except for the wind measurement part. I have written a separate article about it: wind-vane-ver01.shtml. I plan to improve the wind measurement hardware and add it at a later point in time.

For now the weather station has 2 temperature sensors and an air pressure sensor. It works reliable and precise even after several month of testing.

For the sensors we will use:
  • For temperature measurements: LM335. This sensor is cheap and has a linear curve over a wide temperature range. This will give us very accurate temperature readings over a wide range. The accuracy will be almost constant over the whole range.

  • A Motorola/Freescale MPX4115A absolute air pressure sensor. This sensor is already calibrated at production time. The MPX4115A is not made for out-door use but that is not a problem. The circuit can be in a save and dry location inside the house as the air pressure is exactly the same inside and outside the house.

The weather station circuit diagram (add-on board)

 [weather station circuit with LCD, top view]

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