Cảm Biến Khí CO2 Tương Tự Dành Cho Arduino-DFRobot

/*******************Demo for MG-811 Gas Sensor Module V1.1***************************** Author: Tiequan Shao: tiequan.shao@sandboxelectronics.com Peng Wei: peng.wei@sandboxelectronics.com Lisence: Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0) Note: This piece of source code is supposed to be used as a demostration ONLY. More sophisticated calibration is required for industrial field application. Sandbox Electronics 2012-05-31 ************************************************************************************/ /************************Hardware Related Macros************************************/ #define MG_PIN (A0) //define which analog input channel you are going to use #define BOOL_PIN (2) #define DC_GAIN (8.5) //define the DC gain of amplifier /***********************Software Related Macros************************************/ #define READ_SAMPLE_INTERVAL (50) //define how many samples you are going to take in normal operation #define READ_SAMPLE_TIMES (5) //define the time interval(in milisecond) between each samples in //normal operation /**********************Application Related Macros**********************************/ //These two values differ from sensor to sensor. user should derermine this value. #define ZERO_POINT_VOLTAGE (0.220) //define the output of the sensor in volts when the concentration of CO2 is 400PPM #define REACTION_VOLTGAE (0.030) //define the voltage drop of the sensor when move the sensor from air into 1000ppm CO2 /*****************************Globals***********************************************/ float CO2Curve[3] = {2.602,ZERO_POINT_VOLTAGE,(REACTION_VOLTGAE/(2.602-3))}; //two points are taken from the curve. //with these two points, a line is formed which is //"approximately equivalent" to the original curve. //data format:{ x, y, slope}; point1: (lg400, 0.324), point2: (lg4000, 0.280) //slope = ( reaction voltage ) / (log400 –log1000) void setup() { Serial.begin(9600); //UART setup, baudrate = 9600bps pinMode(BOOL_PIN, INPUT); //set pin to input digitalWrite(BOOL_PIN, HIGH); //turn on pullup resistors Serial.print("MG-811 Demostration\n"); } void loop() { int percentage; float volts; volts = MGRead(MG_PIN); Serial.print( "SEN0159:" ); Serial.print(volts); Serial.print( "V " ); percentage = MGGetPercentage(volts,CO2Curve); Serial.print("CO2:"); if (percentage == -1) { Serial.print( "<400" ); } else { Serial.print(percentage); } Serial.print( "ppm" ); Serial.print("\n"); if (digitalRead(BOOL_PIN) ){ Serial.print( "=====BOOL is HIGH======" ); } else { Serial.print( "=====BOOL is LOW======" ); } Serial.print("\n"); delay(500); } /***************************** MGRead ********************************************* Input: mg_pin - analog channel Output: output of SEN-000007 Remarks: This function reads the output of SEN-000007 ************************************************************************************/ float MGRead(int mg_pin) { int i; float v=0; for (i=0;i<READ_SAMPLE_TIMES;i++) { v += analogRead(mg_pin); delay(READ_SAMPLE_INTERVAL); } v = (v/READ_SAMPLE_TIMES) *5/1024 ; return v; } /***************************** MQGetPercentage ********************************** Input: volts - SEN-000007 output measured in volts pcurve - pointer to the curve of the target gas Output: ppm of the target gas Remarks: By using the slope and a point of the line. The x(logarithmic value of ppm) of the line could be derived if y(MG-811 output) is provided. As it is a logarithmic coordinate, power of 10 is used to convert the result to non-logarithmic value. ************************************************************************************/ int MGGetPercentage(float volts, float *pcurve) { if ((volts/DC_GAIN )>=ZERO_POINT_VOLTAGE) { return -1; } else { return pow(10, ((volts/DC_GAIN)-pcurve[1])/pcurve[2]+pcurve[0]); } }