Blog Archives

Cosm Local Environment (Weather) Logger


  • 30-12-2012 – Posts to every 15 minutes (as opposed to every 30 minutes)
  • 30-12-2013 – Multiply atmospheric pressure value by 10 to report hPa rather than kPa (breaks historical data)
  • 30-12-2012 – Changed analog LDR sensor for digital lux light sensor (breaks historical data)
  • 27-12-2012 – Now running from a 5v mains powerpack rather than a 12v SLA battery with maintenance charger. 


  • LCD to display data locally
  • SD card to log data locally for analysis
  • Post to twitter when downtime occurs (with explanation codes – ie. loss of network connection)

Brains of the unit (microcontroller) = Atmel ATmega328

Programmed with Arduino 1.5 (C++) 

Connection to the outside world = WIZ820io
  • Plug-in Network Module having W5200 & Mag Jack
  • Usable without H/W design for W5200, Transformer and RJ-45
Temperature & Humidity = DHT22 temperature-humidity sensor
  • Good for 0-100% humidity readings with 2-5% accuracy
  • Good for -40 to 80°C temperature readings ±0.5°C accuracy 

Atmospehric Pressure = BMP085 Barometric Pressure/Temperature/Altitude Sensor
  • Pressure sensing range: 300-1100 hPa (9000m to -500m above sea level)
  • Up to 0.03hPa / 0.25m resolution

Light = TSL2561 digital luminosity / lux / light sensor

  • Approximates Human eye Response
  • Precisely Measures Illuminance in Diverse Lighting Conditions
  • Dynamic range (Lux): 0.1 to 40,000 Lux