Do you know a simple humidity sensor? I will use it for our project. This sensor will determine if the grain is already dry or not.

 

Do you mean moisture content of the rice or the humidity of the air around the rice?

Most moisture measurement is done using infra-red or radio frequency. Both methods are similar in that they detect how much energy is being absorbed by the moisture. You can have sensors that work off reflected energy or absorption but it really depends on how you are physically going to locate the device.

Chris Jennings