Arduino humidity fan control

This Sketch is used to control an Arduino Nano which is used to get the wet air out of a basement. It'll

• read two DHT22 sensors to get the temperature and humidity from the inside and outside world
• calculate the absolute humidity
• decide, if it is useful to blow the air out
• use a relais to switch on or off a fan
• display data on a 20x4 I2C-LCD
• log the measurements to an SD card, using a RTC module for timestamping

Table of Contents

• How it works
• Wire plan
• Bugs

How it works

Wire plan

Bugs

• the sketch crashes after a random (hours .. days) time due to unknown reason