Humidity

From Refarm the city

build humidity sensors

the humidity sensors of this project are not really sensing humidity:) they sense electro-conductivity i.e. they measure the amount of electricity that goes from one pole to another thought free iones in the water/soil solution.

here is how this works:

-you send 5V from the microcontroller via digital port 2.

-the energy goes straight to one pole of the sensor.

-the other pole receives electricity depending on the mount of water that carries free ions that exists on that 2.45mm distance

-the difference between a dry or wet soil is not big since we are dealing with low voltage. so we use this transistor the 2N2222

that "map" for us the microvoltage into 0-5V

-this value goes to an analog port of the microcontroller that can read from 0 - 1023 values being 0 > 0V and 1023 > 5V and this is a nice resolution to get data:)

the electro-conductivity value has some physical properties that we all must have in our farms in order that we all sense the same:) same in between distance, same metal and the same dimensions. all this characteristics have influence on the readings. we still don't have any idea how does the chemistry of the soil will change the readings.

-should be in gold for long lasting

-should be small to save resources

-should be cheap to be affordable to mainstream

-should be easy to reply.

-must be environmentally safe.

after a lot of research we found this object that almost fits our needs. a 2.45mm break away headers pins covered with gold. they cost about 1€ and you can get 15 sensors. this price is unbeatable:)