It has been a busy week with Halloween and some unforeseen breakdowns on the farm. we will be catching up on a slow week today.

 

CO2 is an important factor in plant growth, in some instances sealed grow rooms run at a artificiality elevated CO2 concentration. We wont be doing this in the greenhouse but it would be nice to have a fully defined set of growing conditions for comparing experiments.

 

DfRobot have been kind enough to send me out a PH sensor and CO2 sensor to keep the project moving along quickly, so we will be using the parts from them:

 

CO2 Sensor (Arduino compatible)

[You can most likely source the parts from elsewhere]

 

I will wire the sensor up and talk about how it performs in the next blog on CO2, I think we need to find a cheap way to calibrate the sensors as not everyone is going to have access to CO2 calibration gases [I certainly dont]. Looking at the spec sheet[for the MG811] it might not need calibration, a real life test will be needed to confirm this.

 

Wiring diagram:

pinout

 

 

Header 1

/*

   CO2 Sensor Gas:

 

This script allows you to use a analog c02 gas sensor [like the one in the link below]:

 

 

http://www.dfrobot.com/index.php?route=product/product&product_id=1023&search=co2&description=true#.VjeKyXzhDVM

 

 

 

 

Procedure:

>warm sensor up and take a reading of two known c02 solutions  [note down ADC readout and c02 ppm]

>plug the numbers into the top of the code [Lines 28-31]

>see if it works with a amonia solution between the min and max you calibrated with.

 

 

 

 

other info:

>Burn Sensor in for a hour or so before stable readings will be had

>Sensor needs time to warm up after being powered up

 

 

 

 

 

 

 

   25/10/2015  Michael   Ratcliffe

   

   

          This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation, either version 3 of the License, or

    (at your option) any later version.

 

 

    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.

 

 

    You should have received a copy of the GNU General Public License

    along with this program.  If not, see <http://www.gnu.org/licenses/>.

 

Sensors and useful info:

>Gas Sensor needs burning in before first use

>

 

 

*/

 

 

int GasPin=A0;

float CO2MinADC=0;

float CO2MaxADC=0;

float CO2MinPPM=0;

float CO2MaxPPM=0;

 

 

//We will proberbly have to correct for temperature in the long run [not used yet]

float Temperature=0;

float Temp_Coef=0;

float Offset=0;

 

 

//[Im guessing it will be liner with a offset]

 

 

int i=0;

int SensorBuffer=0;

float CO2PPM=0;

float Gas_Readout=0; //Float incase we attempt to change ADC to PPM

// ************************ Setup Routine ********************************//

void setup() {

 

 

  Serial.begin(9600);// turn serial coms on for sending data to pc

  Setup_Info();

 

}

 

 

//************************** Main Loop ***********************************//

//************************************************************************//

void loop() {

      //Taking ten readings and averaging for accuracy

      i=1;

      SensorBuffer=0;

      while(i<=10){

      Gas_Readout= analogRead(GasPin);

      SensorBuffer=SensorBuffer+Gas_Readout;

      delay(50);

      i++;

      };

      Gas_Readout=SensorBuffer/i;  // cheack that my maths is correct her, I usssualy cock up this bit by one iteration

    

Map_Results();

Print_Results();

 

 

 

 

}

 

 

//*************** Printing dome useful info to seerial on boot up *********//

void Setup_Info(){

Serial.println("This script is a proof of concept that we can get useful representation of amonia in water by measuring its gas off");

Serial.println("Gas Sensor needs burning in before first use [30 mins minimum]");

Serial.println("Calibrate, take ADC read out at MAX CO2 and Min and put them in the top od code");

 

 

 

}

 

 

 

 

 

 

//****************Maps Results after we have Calibration values************//

void Map_Results(){

 

 

// Map only gives integers, we will need to modify to get better readings  [thats what all the *100 are about

CO2PPM = map(Gas_Readout*100, CO2MinADC*100, CO2MaxADC*100, CO2MinPPM*100, CO2MaxPPM*100);

CO2PPM=CO2PPM/100;

 

}

 

 

//********************Print something useful to Serial here****************//

void Print_Results(){

Serial.println("NEW RESULTS ");

Serial.print("ADC Gas Sensor: ");

Serial.println(Gas_Readout);

Serial.print("Amonia PPM: ");

Serial.println(CO2PPM);

 

};

 

 

 

 

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