Problems calibrating the SparkFun Soil Moisture Sensor

Hello everyone,

I've been having trouble calibrating the Spark Fun sensor with my UNO. All the other guides I've seen, it's worked out of the box for them once they connected it to the appropriate pins. For me, the only 2 outputs that seem correct are, a 0 reading when in the air, and a high reading, around 900-ish when submerged in water.

The pin has 3 connections, VCC, GND, and SIG, and I have set them to a Digital PIN, GND, and A0 respectively.

Every other soil that I've dipped the sensor into, only gives the same output as if it were in water, which is wrong.

I just wanted to know, is the sensor just not "sensitive enough", or am I doing something wrong?

I also have not soldered the jumper wires into the sensor, I just curved them into a J shape in order to hold it in, could that be causing an error in my readings?

That sensor is poorly designed but the design is commonly found on the web. As google will show, lots of people have reported problems with it.

You should always solder connections, and [u]especially[/u] if they will be exposed to dampness.

jremington: That sensor is poorly designed but commonly found on the web. As google will show, lots of people have reported problems with it.

You should always solder connections, and [u]especially[/u] if they will be exposed to dampness.

Ok, thanks for the advice, is it to ask for a review of any good, and affordable soil moisture sensor(s)? The ones I've had my eye on are the DFRobot Gravity, and Gravity Resistance.

I have only exposed the probes of the sensor into water, and have made sure that the connectors haven't made any contact with water.

You'll have to do some research. I have seen reports of decent soil moisture meters that work with capacitive sensors, but didn't keep notes.

Measuring soil moisture accurately and reproducibly is a difficult problem, because soils are all different. A single design won't work for all soils, and current flowing through the probe affects the soil by inducing chemical reactions.

HI

Did you ever figure out your Capacitive Moisture sensor? I was concerned that you suggested you were using a digital pin. My capacitive sensor uses 3v, Gnd, and A0 or other analog input pin. I found that i had to take readings with the probe and calibrate the sketch with these readings which were higher then the example code. the voltage for my probe can be 3 -5V but should match the normal operating voltage of the MCU being used. 3-5v for Arduino uno or 3.3V for ESP32 or MKR1000.

hope this helps someone. I'll try to post back as I figure mine out. keep the bits flowing