If you’re looking to measure the humidity in your space, this project uses a cool terrarium-style light bulb with LEDs.via emdee401 on instructablesThis arduino controlled LED light changes color when the humidity is not optimal.
Whenever the humidity is below 40%, the color will change to Red
Between 40 and 60% the color will be green
Above 60%, the color will change to Yellow! // Read more: original article.
