Hey there,
I'm pretty new to arduino but somewhat familiar with electronics and stuff.
I'm currently working on setting up an automated (ultra low cost) greenhouse controller based on arduino and i am already doing pretty good progress.
It's the third day i've had my little microcontroller friend and already diy-ed a working soil humidity, temperature and air humidity sensors.
They all work great, only the air humidity sensor readings still confuse me.
I got that sensor from some old digital thermometer/hygrometer thing, together with a fitting resistor (smd size, but i managed to solder some wires into it for the breadboard).
Anyways, the readings are somehow weird. When it's set up in a room and i breathe onto the sensor, the value reported by arduino goes up, leading me to think that higher humidity -> higher value
However in long term tests with nearly constant humidity but falling temperature (2 hours, 50% relative humidity, temperature drop from 20.5 to 18 something celsius) i noticed that the values of the humidity sensor keep falling. First they read something around 180, now theyre already at 130 and dropping, but the humidity is still pretty much the same (as measured by another digital hygrometer next to the breadboard.)
Can anyone give me some insight on how resistive hygrometer sensors work? Is this behavior somehow related to the temperature?
I'm not aiming to calibrate the readings into some unit that i can actually relate to something. I just need the sensor values for regulating the climate, so knowing that value xx is xx % humidity or xx C° temperature is already enough.
