TDS meter not responding

[gvidmar]

Hi guys, i am still quite new to this and this most likely has a small problem that i am not seing but i have really tried everything on my own and i simply give up at this point..
My tds meter is not responding at all. I went to absolute basics, just connected it to 5V, GND and A1.
I downloaded a sample code just to see if i could see the ppm in the serial monitor and all i get are these question marks. Any ideas why?
I want it to work together with temp sensor but for starters it would be awesome if it responded on its own.
Sensor: LINK

#include <EEPROM.h>
#include "GravityTDS.h"

#define TdsSensorPin A1
GravityTDS gravityTds;

float temperature = 25,tdsValue = 0;

void setup()
{
    Serial.begin(115200);
    gravityTds.setPin(TdsSensorPin);
    gravityTds.setAref(5.0);  //reference voltage on ADC, default 5.0V on Arduino UNO
    gravityTds.setAdcRange(1024);  //1024 for 10bit ADC;4096 for 12bit ADC
    gravityTds.begin();  //initialization
}

void loop()
{
    //temperature = readTemperature();  //add your temperature sensor and read it
    gravityTds.setTemperature(temperature);  // set the temperature and execute temperature compensation
    gravityTds.update();  //sample and calculate
    tdsValue = gravityTds.getTdsValue();  // then get the value
    Serial.print(tdsValue,0);
    Serial.println("ppm");
    delay(1000);
}

[jremington]

Do you have the sense prongs in a test solution of some sort? Which Arduino?

all i get are these question marks.

Did you set the serial Baud rate correctly in the serial monitor?

Please post a close up, focused photo of your setup.

[StefanL38]

your code uses

Serial.begin(115200);

115200 baud is the modern standard.
Though the arduino-IDE is set to 9600 baud by default.

So maybe adjusting the baudraute to 115200 baud in the Ardiuni-IDE will do it.
If not post the datasheet of your TDS-meter and which exact microcontroller you are using
here is code-version which does the same with non-blocking timing
and a heartbeat-blinker with the onboard-LED
assuming that you are using Arduino Uno or Mega

#include <EEPROM.h>
#include "GravityTDS.h"

#define TdsSensorPin A1
GravityTDS gravityTds;

float temperature = 25,tdsValue = 0;

// declaring a timer-variable for NON-blocking timing
unsigned long MyTestTimer = 0; // Timer-variables MUST be of type unsigned long
unsigned long MyBlinkTimer = 0; // Timer-variables MUST be of type unsigned long
const byte onBoard_LED = 13;


void setup() {
    Serial.begin(115200);
    Serial.println("Setup-Start");
    pinMode(onBoard_LED,OUTPUT);
    gravityTds.setPin(TdsSensorPin);
    gravityTds.setAref(5.0);  //reference voltage on ADC, default 5.0V on Arduino UNO
    gravityTds.setAdcRange(1024);  //1024 for 10bit ADC;4096 for 12bit ADC
    gravityTds.begin();  //initialization
}

void loop() {
  blinkLED() 
  
  // check if 1005 milliseconds have passed by since last time
  if ( TimePeriodIsOver(MyTestTimer,1005) ) {
    // if REALLY 1005 milliseconds have passed by
    //temperature = readTemperature();  //add your temperature sensor and read it
    gravityTds.setTemperature(temperature);  // set the temperature and execute temperature compensation
    gravityTds.update();  //sample and calculate
    tdsValue = gravityTds.getTdsValue();  // then get the value
    Serial.print(tdsValue,0);
    Serial.println(" ppm");
    // delay(1000); no delay needed with TimePeriodIsOver()
}

// easy to use helper-function for non-blocking timing
boolean TimePeriodIsOver (unsigned long &startOfPeriod, unsigned long TimePeriod) {
  unsigned long currentMillis  = millis();
  if ( currentMillis - startOfPeriod >= TimePeriod ) {
    // more time than TimePeriod has elapsed since last time if-condition was true
    startOfPeriod = currentMillis; // a new period starts right here so set new starttime
    return true;
  }
  else return false;            // actual TimePeriod is NOT yet over
}


void blinkLED() {
  // check if 250 milliseconds have passed by since last time
  if ( TimePeriodIsOver(MyBlinkTimer,250) ) {
    // if REALLY 250 milliseconds have passed by
    if (digitalRead(onBoard_LED) == HIGH) ) {
      digitalWrite(onBoard_LED,LOW);       
    }
    else {
      digitalWrite(onBoard_LED,HIGH);             
    }
  }
}

best regards Stefan

[kolaha]

@gvidmar your provided sketch is the most overcomplicated Analog-to-Serial sketch I have ever seen

[StefanL38]

@kolaha

this is the most overcomplicated Analog-to-Serial sketch I have ever seen

it is more than just analog to serial. Pure serial would require just this

void setup() {
    Serial.begin(115200);
    Serial.println("Setup-Start");
}

void loop() {
 Serial.println("Hello World");    
 delay(1000); 
}

and would guide newcomers on the path of

• stuff everything into void loop()
• use delay() (and get problems later)

my sketch shows:

• how to structure code into functions where each function does one thing
• non-blocking timing encapsulted into a function which makes non-blocking timing easier to understand
• a heartbeat-blinker to indicate code is really running

[gvidmar]

I changed do 9600 and it works now.
Like i said its probably something really simple and stupid
Thank you!

[StefanL38]

sounds like you changed

@StefanL38

Serial.begin(115200);

to

Serial.begin(9600);

The other option is
to change from

to

in the serial monitor

The baudrates in the code and the baudrate of the serial monitor must match

best regards Stefan