Moisture Sensor(Industrial ?) for Irrigation ?

Hi..
If i Google the moisture sensor it will show me these..

But I am Looking for one Actually I can use in Field...
So I Googled little harder and end up with following two sensors

  1. seeed studio moisture and Temperature sensor
    http://www.seeedstudio.com/depot/Soil-Moisture-Temperature-Sensor-p-1356.html

  2. watermark soil sensor moisture
    Watermark Soil Moisture Sensor

So is Seeed studio sensor Really Moisture sensor ? its Wiki saying it is a Soil moisture sensor But the Datasheet provided sth10 saying it is humidity sensor ?

is it gonna survive if put the sensor below two feet in the soil ?

And Can anyone tell me how to interface water mark soil moisture sensor to the arduino ? I did found this one http://www.emesystems.com/smx.htm.

Does anybody know how to make diy version of this?

I think the Seeed and the Watermark sensors are the same thing. The Watermark looks like it has a plastic housing of some sort, and lacks the heavy-duty cable. Look for reviews to see what people have said about their reliability, or buy one and bury it.

On the other hand, you could try taking a couple 2-foot lengths of insulated. copper wire, strip an inch or so at the end, tape them so the ends don't touch, and bury that. Test the resistance under varying watering conditions.

ChrisTenone:
I think the Seeed and the Watermark sensors are the same thing.

Hi, Thanks for Reply..
Seeed Studio sensor uses sth10 (i think.. they linked its datasheet to it). In datasheet it is given as humidity & Temp sensor.

Seed studio wiki page Seeed Studio Bazaar, The IoT Hardware enabler.
link to Datasheets http://www.seeedstudio.com/document/rar/datasheet.zip

So Is Seed studio moisture sensor more like DTH11 ?

buy one and bury it

In India the sensors coming at two times original cost.. So I need to choose Which is more Useful For Me

http://wemakethings.net/chirp/

Open source
Chirp is Open Source Hardware available under CERN Open Hardware Licence v.1.1.
All the schematics and code is available at GitHub - Miceuz/PlantWateringAlarm: A soil humidity level sensor based on ATTINY44. Uses capacitive sensing..

anilkunchalaece:
But I am Looking for one Actually I can use in Field…

Like stick in the ground/measure/remove?

I think you can’t do that with cheap resistive sensors (your picture).
They need a resting rusting period.
And if you leave a circuit board in the ground, it won’t last very long.
I think two 3" or 4" nails, 1" apart, is as good as those cheap resistive sensors.

I have a project going with two 3" nails permanently in the soil (potplant).
With an AC (not DC) measuring current.
Quite useable if you wait three days for the nails to settle (water frequently).
This resistive measuring method is somewhat temp dependent though.

No experience (yet) with capacitive sensors, like the chirp.
Seems ok for indoors (flower pots), but not for “in the field”.
Too many exposed parts.

Attached is partially tested code if you want to experiment with “two nails in the ground”.
You might have to play with the values (after three days).
Leo…

/*----Soil Moisture Sensor----
  Two (galvanised) 3" nails, 1" apart
  10k resistor from D5 to A0
  47uF cap positive to A0 and negative to the first electrode
  Second electrode connected to Arduino ground
  Use twisted or shielded wire for long runs  e.g. Cat-5
*/

const byte drivePin = 5,
           samples = 25; // min one PWM period time | max 64 samples
unsigned long currentMillis,
         previousMillis,
         interval = 10; // sampling interval in minutes
int rawValue, // A/D reading
    highPeak = 0, // start low
    lowPeak = 1023, // start high
    highValue = 240, // 100% dry
    lowValue = 40, // 100% wet
    dryValue; // dry value
byte moisture; // moisture percentage

void setup() {
  pinMode(drivePin, OUTPUT);
  analogWrite(drivePin, 128); // 1kHz square wave on pin 5
  Serial.begin(9600);
  Serial.print(F("Soil Moisture Sensor"));
  Serial.print(F("\t Sample interval = "));
  Serial.print(interval);
  Serial.println(F(" minutes"));
  Serial.println(F("===================="));
  interval = interval * 60000; // change to millis
  previousMillis = millis() - interval + 3000; // first reading after 3 seconds
}

void loop() {
  currentMillis = millis(); // update
  if (currentMillis > previousMillis + interval) {
    for (int x = 0; x < samples; x++) {
      rawValue = analogRead(A0);
      if (rawValue > highPeak) { // detect highest peak
        highPeak = rawValue;
      }
      if (rawValue < lowPeak) { // detect lowest peak
        lowPeak = rawValue;
      }
    }
    dryValue = highPeak - lowPeak; // calculate difference
    highPeak = 0; // reset
    lowPeak = 1023; // reset
    previousMillis = currentMillis; // update
    Serial.print(F("Raw="));
    Serial.print(dryValue); // higher is drier
    dryValue = constrain(dryValue, lowValue, highValue);
    moisture = map(dryValue, highValue, lowValue, 0, 100); // invert and map to 0-100%
    Serial.print(F("\t Soil moisture is ")); // higher is wetter
    Serial.print(moisture);
    Serial.println(F("%"));
  }
}

@Wawa
Thankyou for Reply..
I am looking for Which one of above sensor is best suitable for My Application

anilkunchalaece:
@Wawa
Thankyou for Reply..
I am looking for Which one of above sensor is best suitable for My Application

We still do not know your application.

water level at the surface will always be less than at depth after some settling.
it will always be higher after watering or rain.

most plant roots have a shallow depth, 2/3 meter deep is very deep for roots. that is if you are trying to use this for agriculture.

Consider that a simple enclosure on any of these will allow them to be burried.
you can dig a small well, put in stones, brick or pipe and place the soil sensor at depth.
make sure you make it air tight so there is no effect from the surface.
you can put on the end of a long probe and insert to depth. maybe need to 'drill' a hole so that insertion is easier.

There are firms which build these for farmers....

they use a high frequency excition ac source, and detect the conducted current

dc won't do as it polarises the electrodes and gives false readings.

regards

Allan.

It sounds like you are looking for something that will last. That means the cost will be high. Maybe 100-200USD. Take a look at SDI-12 sensors. They're what agriculture and environmental research usually use. Take a look at Decagon 5TM volumetric water content and temperature sensor.

Seems most of these expensive resistive sensors are the equivalent of "two nails in the ground".
The better ones with diurnal temp compensation.

OP is asking for DIY.
If this is for permanent deep soil, I would try two long evenly spaced stainless welding rods, or the sliding rods from an old flatbed scanner. Maybe embedded in gypsum. With e.g. a DS18B20 temp sensor.

The code from post#4 uses a ~1kHz square wave signal, sent to the sensor via a 10k resistor.
The sensor shorts part of this AC signal to ground via a cap (no corroding DC on the sensor).
Remaining peak/peak signal on the sensor is measured by an analogue pin.

Allan mentioned a high frequency. Not sure if that's needed for a simple setup.
Not a problem to change the drive pin to a higher frequency with code though.
Then the 47uF cap can be a lower value too.
Leo..

Some more reading.

Decagon sensor is cap sensing. I thought OP asked industrial sensor.

liudr:
Decagon sensor is cap sensing. I thought OP asked industrial sensor.

I see at least two types on their website.
Electrical conductivity and dielectric permittivity.
Leo..

Did you read the 5TM then? That's the one I recommended.

liudr:
Did you read the 5TM then? That's the one I recommended.

At $155, I think it is out of his price range.

2 pieces of metal in some qypsom might be easier.

Wawa:
Some more reading.
http://vanderleevineyard.com/1/post/2012/07/the-vinduino-project-2-making-and-installing-gypsum-soil-moisture-sensors.html

That’s a Quite good information i am looking for. Thanks for it Wawa

dave-in-nj:
2 pieces of metal in some qypsom might be easier.

I will try this…

dave-in-nj:
We still do not know your application.

My Application is Measuring the Moisture at root Level

My main concern over using some bare metal probes is that once the OP is all done, measurement values will drift over time so the next student will look at the data and become confused. Are there any glass covered probe that are used as cheap alternatives?

liudr:
My main concern over using some bare metal probes is that once the OP is all done, measurement values will drift over time so the next student will look at the data and become confused. Are there any glass covered probe that are used as cheap alternatives?

calibration and testing will always be required.
for the use of sensors at depth, one might be well served to install a pipe and then insert said sensor at the base of the pipe.

that way one could use a seccondary probe to test and calibrate without having to dig up the sensor and disturb the soil.

as a note, capacitive sensors are not prone to decay from electrolosys, could be encapusulated to make an environmental shield and at 2 feet of depth, there would be less change of temperatures and effects of people would be reduced.

I've worked on these devices professionally.

We used 100MHz as exitation.

The point is that different soil types have different characteristics - it affects both the conductivity and the dielectric constant.

calibration for water content was done by taking a sample, weighing it, then drying in an oven at about 120C and weighing again....

how accurate do you want to be? if you're not in a hurry the oven method is best..

regards

Allan

allanhurst:
We used 100MHz as exitation.

Must have been a capacitive sensor.
The small cap variation of the sensor influencing the frequency of a VHF oscillator more.
Leo..

Yes, it was. Mostly. The drive frequency was fixed, not part of a free-running oscillator.

Obviously the impedance of wet soil is both capacitive and resistive, but at 100MHz the capacitive part dominates.

One reason for this approach is that fertilisers such as ammonium nitrate are ionic, and small amounts affect the conductivity enormously.

But not the dielectric constant.

regards

Allan