Question 1

do you have a library for the arduino?  How do I calibrate these?  Getting an analog reading does not mean anything..

Accepted Answer

Take a reading while they are dry (that's your 0% reading), then take a sample of your soil and put it in a pot, insert the sensor and then water the pot until it can't hold any more water, then take another reading that's 100% saturated.
If you want you can put the sensor near a plant and see what level it reads when the plant looks stressed from to little water and make sure you keep it wetter than that.
Note: unless you are measuring pots, the moisture level near the surface is about useless for most plants unless they have very shallow roots..  for plants with deeper roots you probably want to waterproof the top portion of the sensor and bury it about 18" down.

Question 2

What is the max distance from a pi  using 3v3 and using cat5 cable can the sensor be and still work ok?

Accepted Answer

so not sure if you still need this answered or not, but for others it might help.
Im using an Arduino 5v, I used about 10 feet of cat5 cable from arduino to sensor. it changed the value some but you just need to calibrate it for that change.
example,
Arduino to senor without cat 5 = wet "850" / dry "450"
arduino to sensor with 10 feet cat 5 =  wet "700" /dry "300"

Question 3

how does this work? do i have to connected to something else?

Accepted Answer

Yes. Depends on what you want to do with it.
The output is a voltage value. You can connect to an Adruino type device to display it as analog or convert it to a calibrated digital display of percent moisture.

Question 4

Will this work (as is) with the Micro:bit?

Accepted Answer

I dont know understand your question. I plugged it into a data port on a esp 8266 read the data using C+ and  calibtrated it to meet my needs and transmitted it to a Blynk Control Panel  on the internet.

Manufacturer	Songhe
Part number	F24
Item Weight	90 g
Product Dimensions	9.8 x 2.3 x 1 cm; 90 g
Item model number	F24
Style	Modern
Material	Ceramic, Metal
Voltage	5.5 Volts
Item Package Quantity	1
Measurement Accuracy	±15%
Specific uses	Intelligent agriculture, Moisture detection, Garden plants
Batteries included?	No
Batteries Required?	No

Songhe Capacitive Soil Moisture Sensor Module Corrosion Resistant W/Gravity for Arduino Moisture Detection Garden Watering DIY 3.3~5.5V 5pcs

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