Litter Box Monitor
Keeping the house smelling nice with four cats in residence can be quite a challenge. To help make sure the litter boxes are scooped and changes as appropriate, I am working on a prototype that monitors the air quality near the boxes and then sends a text message to alert someone to do their chore (aka my daughter).
So far, the prototype centers around an MQ135 air quality sensor that includes ammonia amongst the gases it can detect. As the air quality worsens, the voltage read from the sensor increases.
The first prototype was done using an Arduino Yun with data being logged to a MicroSD card. After confirming the the sensor was functioning as desired and seeing how the readings behaved in correlation with the smell around the litter box, I came up with a data model that would work for knowing when the litter needed to be changed.
The next version of the prototype will use an ESP8266 Thing from SparkFun to reduce the cost quite a bit.