Hi all ! Hope everyone is safe and sound !
This post is just to share the contraption I made to read the PH level of the water. Because the PH sensor cannot stay in water for long - like the TDS sensor - I've build a small contraption to read the PH level and display it in a TFT screen I had laying around.
Here's the schematics of the build:
The build is nothing fancy - a small wooden box with holes to the power button
Code
To be able to use the PH sensor, it had to be calibrated. Using a PH 7.0 solution just for these purpose, I was able to calibrate it .
Note: The following code is not mine. I've taken it from https://scidle.com/how-to-use-a-ph-sensor-with-arduino/ . It works very well. In the second listing, I've just altered the code to be used with the TFT screen.
Here's the code used for calibration.
/*
# This sample code is used to test the pH meter V1.0.
# Editor : YouYou
# Ver : 1.0
# Product: analog pH meter
# SKU : SEN0161
*/
#define SensorPin A0 //pH meter Analog output to Arduino Analog Input 0
#define Offset -1.18 //deviation compensate
#define LED 13
#define samplingInterval 20
#define printInterval 800
#define ArrayLenth 40 //times of collection
int pHArray[ArrayLenth]; //Store the average value of the sensor feedback
int pHArrayIndex=0;
void setup(void) {
pinMode(LED,OUTPUT);
Serial.begin(9600);
Serial.println("pH meter experiment!"); //Test the serial monitor
}
void loop(void) {
static unsigned long samplingTime = millis();
static unsigned long printTime = millis();
static float pHValue,voltage;
if(millis()-samplingTime > samplingInterval) {
pHArray[pHArrayIndex++]=analogRead(SensorPin);
if(pHArrayIndex==ArrayLenth)pHArrayIndex=0;
voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;
pHValue = 3.5*voltage+Offset;
samplingTime=millis();
}
if(millis() - printTime > printInterval) { //Every 800 milliseconds, print a numerical, convert the state of the LED indicator
Serial.print("Voltage:");
Serial.print(voltage,2);
Serial.print(" pH value: ");
Serial.println(pHValue,2);
digitalWrite(LED,digitalRead(LED)^1);
printTime=millis();
}
}
double avergearray(int* arr, int number) {
int i;
int max,min;
double avg;
long amount=0;
if (number<=0) {
Serial.println("Error number for the array to avraging!/n");
return 0;
}
if (number<5) { //less than 5, calculated directly statistics
for(i=0;i<number;i++) {
amount+=arr[i];
}
avg = amount/number;
return avg;
} else {
if (arr[0]<arr[1]) {
min = arr[0];max=arr[1];
}
else {
min=arr[1];max=arr[0];
}
for(i=2;i<number;i++) {
if (arr[i]<min) {
amount+=min; //arr<min
min=arr[i];
} else {
if (arr[i]>max) {
amount+=max; //arr>max
max=arr[i];
} else {
amount+=arr[i]; //min<=arr<=max
}
}//if
}//for
avg = (double)amount/(number-2);
} //if
return avg;
}
Basically what the codes does is takes 40 samples in a question of milliseconds and shows the average value.
Now here's the code adapted for the LCD and with the offset necessary after calibration.
/*
# Measure PH level
# Editor : Feiticeir0
# Ver : 1.0
# Product: analog pH meter
*/
#include <SPI.h>
#include <TFT.h>
//TFT PINS
#define cs 10
#define dc 9
#define reset 8
TFT tftScreen = TFT (cs, dc, reset);
#define SensorPin A0 //pH meter Analog output to Arduino Analog Input 0
#define Offset -1.18 //deviation compensate
#define LED 13
#define samplingInterval 20
#define printInterval 800
#define ArrayLenth 40 //times of collection
int pHArray[ArrayLenth]; //Store the average value of the sensor feedback
int pHArrayIndex=0;
char vprint[4];
char pprint[4];
void setup(void) {
pinMode(LED,OUTPUT);
Serial.begin(9600);
/* dont have more 5v outputs.. TEMP */
pinMode (7, OUTPUT);
digitalWrite(7,HIGH);
tftScreen.begin();
tftScreen.background(0,0,0); // clear the screen
tftScreen.setTextSize(1);
//line split voltage and PH
tftScreen.stroke(255,255,255);
//tftScreen.line(0,64,160,64);
tftScreen.fill(255,255,255);
tftScreen.rect(0,63,160,3);
tftScreen.text("PH reading ",2,0);
tftScreen.text("Voltage ",2,67);
tftScreen.setTextSize(3);
}
void loop(void) {
static unsigned long samplingTime = millis();
static unsigned long printTime = millis();
static float pHValue,voltage;
if (millis() - samplingTime > samplingInterval) {
pHArray[pHArrayIndex++]=analogRead(SensorPin);
if (pHArrayIndex==ArrayLenth)
pHArrayIndex = 0;
voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;
pHValue = 3.5*voltage+Offset;
samplingTime=millis();
}
if (millis() - printTime > printInterval) { //Every 800 milliseconds, print a numerical, convert the state of the LED indicator
String volts = String(voltage);
String ph = String(pHValue);
volts.toCharArray(vprint,4);
ph.toCharArray(pprint,4);
tftScreen.stroke(255,255,0);
tftScreen.text(vprint, 60,84);
tftScreen.text(pprint, 60,20);
delay(500);
//set to black to erase
tftScreen.stroke(0,0,0);
tftScreen.text(vprint, 60, 84);
tftScreen.text(pprint, 60,20);
//digitalWrite(LED,digitalRead(LED)^1);
printTime = millis();
}
}
double avergearray(int* arr, int number){
int i;
int max,min;
double avg;
long amount=0;
if (number<=0) {
Serial.println("Error number for the array to avraging!/n");
return 0;
}
if (number<5) { //less than 5, calculated directly statistics
for(i=0;i<number;i++) {
amount+=arr[i];
}
avg = amount/number;
return avg;
} else {
if(arr[0]<arr[1]) {
min = arr[0];max=arr[1];
}
else {
min=arr[1];max=arr[0];
}
for(i=2;i<number;i++) {
if(arr[i]<min) {
amount+=min; //arr<min
min=arr[i];
} else {
if (arr[i]>max) {
amount+=max; //arr>max
max=arr[i];
} else {
amount+=arr[i]; //min<=arr<=max
}
} //if
} //for
avg = (double)amount/(number-2);
}//if
return avg;
}
With this, I'm able to use the sensor anytime !
Happy coding.
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