Analog input 'Tare/Zero' Weight Function

Just paste the sketch into www.pastebin.com and return the link. Its makes it clean for looking at. If you want to get real fancy, select c++ highlighting.

Hi,

I have joined Pastebin and pasted the code but how do you save it?

Hi,

I have joined Pastebin and pasted the code but how do you save it?

Gordon

You can just paste it here

There are various options if you click the Advanced Editor in top right, and then select the double chevron

However none of them do much except the quote.

Most people just dump it here, but he developers are meant to be working on a more eligant method.

Mark

 

#include <SD.h>

int CS_pin = 10;
int pow_pin = 8;
const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to
float sensorValue = 0;       // value read from the pot
int switchState = 0;         // Dat enter push button.
int led = 9;                // Data transfered LED
const int buttonPin = 3;     /// the number of the Tare/Zero pushbutton pin
int buttonState = 0;         /// variable for reading the pushbutton status
int TareValue;
int FinalWt;

void setup() {
    // initialize serial communications at 9600 bps:
  Serial.begin(9600);
  Serial.println("Initializing Card");
  //CS Pin is an output
  pinMode(CS_pin, OUTPUT);
 
  //Card will draw power from Pin 8, so set High
  pinMode(pow_pin, OUTPUT);
  digitalWrite(pow_pin, HIGH);
 
  //Check card is ready
  if(SD.begin(CS_pin))
{
  Serial.println("Card Failed");
  return;
}
Serial.println("Card Ready");

}
void loop() {
// read the Tare input pin:
  buttonState = digitalRead(buttonPin);
  if (buttonState == HIGH){
  int TareValue = analogRead(A0);
  Serial.println (TareValue);
  }
{
  String dataString = "Results";
 
  //Open a file to write to, only one at a time.
  File dataFile = SD.open("DATAFILE.TXT", FILE_WRITE);
  if(dataFile)
 
  {
    dataFile.println(dataString);
    dataFile.close();
    Serial.println(dataString);
  }
  //else
  {
    // Serial.println("Couldn't access file");
  }
  delay(1000);
  //pinMode(buttonPin, INPUT);
  //int TareValue = analogRead(A0);
  //int FinalWt = sensorValue - TareValue;

  // read the analog in value:
  sensorValue = analogRead(0) / 4.26;(analogInPin);
  sensorValue = sensorValue / 16;
  //sensorValue = analogRead(0) / 0.1024;(analogInPin);
  //sensorValue = sensorValue / 1000;
  pinMode(led, OUTPUT);
 
  switchState = digitalRead(2);
 
  if (switchState == HIGH){
 
  FinalWt = (analogRead(0) - TareValue);
  //int FinalWt = 100 - 25;
  // print the results to the serial monitor:
  Serial.println(FinalWt);
  Serial.print(analogRead(0));
  Serial.print(" weight = " ); 
  Serial.print(sensorValue);
  Serial.print(" lbs/oz");
  ///Serial.print(" K/g");
  Serial.println ();
  digitalWrite(led, HIGH);
  delay(100);               // wait for a 100ms
  digitalWrite(led, LOW);

  // wait 400ms before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(400);                    
  }
  }
}

Hi Mark,

I hope you have received the code at last, don't forget it is my first attempt so there may be some unnecessary code.

Can you let me know if you have received it please.

Regards,

Gordon

Gordon

Seen your message.

Give me some time with it, and I'll respond.

In the meantime feel free to try yourself, you'll never know until you try.

I always find that sitting down with a piece of paper and block representation of what I'm trying to achieve helps ...(or not).

Worrying about what the code is, doesn't always help since there are often multiple ways to achieve it.

Personally I don't worry about how 'tight' my code is, since the micro is mostly just waiting around, as in your case.

The areas to concentrate on is the HMI (Human 'micro' Interface) since pushing the button and wondering is never a good look.

cheers

Mark

Gordon

I've made some changes and added comments to make them a little more obvious

I think one of the stumbling blocks was not resetting the buttonState after you had done what was necessary.

Each time it looped back it assummed the button was pressed and did the Tare/Zero thing.

#include <SD.h>

 

int CS_pin = 10;

int pow_pin = 8;

const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to

float sensorValue = 0;       // value read from the pot

 

// ** changed

int switchState = 2;         // Dat enter push button.

// *******

 

int led = 9;                // Data transfered LED

const int buttonPin = 3;     /// the number of the Tare/Zero pushbutton pin

int buttonState = 0;         /// variable for reading the pushbutton status

int TareValue;

int FinalWt;

 

void setup() {

    // initialize serial communications at 9600 bps:

  Serial.begin(9600);

  Serial.println("Initializing Card");

 

  // ****Added these pinModes *****

  //inputs

  pinMode(switchState, INPUT);    //digital input 2

  pinMode(buttonPin, INPUT);      //digital input 3

 

  //outputs

  pinMode (led, OUTPUT);    //led on pin 9  ...needs to be set otherwise its very dull.

 

  // ***********

 

  //CS Pin is an output

  pinMode(CS_pin, OUTPUT);

 

  //Card will draw power from Pin 8, so set High

  pinMode(pow_pin, OUTPUT);

  digitalWrite(pow_pin, HIGH);

 

  //Check card is ready

  if(SD.begin(CS_pin))

{

  Serial.println("Card Failed");

  return;

}

Serial.println("Card Ready");

 

}

void loop()

{

// read the Tare input pin:

  buttonState = digitalRead(buttonPin);

 

  if (buttonState == HIGH)    // Tare/Zero button pressed

  {

    int TareValue = analogRead(A0);

    Serial.println (TareValue);

    buttonState = LOW; // *** need to reset this once you've done whats needed ****

  }

 

  String dataString = "Results";

 

  //Open a file to write to, only one at a time.

  File dataFile = SD.open("DATAFILE.TXT", FILE_WRITE);

  if(dataFile)

   {

      dataFile.println(dataString);

      dataFile.close();

      Serial.println(dataString);

   }

  //else

  {

    // Serial.println("Couldn't access file");

  }

  delay(1000);

  //pinMode(buttonPin, INPUT);

  //int TareValue = analogRead(A0);

  //int FinalWt = sensorValue - TareValue;

 

  // read the analog in value:

  sensorValue = analogRead(0) / 4.26;(analogInPin);

  sensorValue = sensorValue / 16;

  //sensorValue = analogRead(0) / 0.1024;(analogInPin);

  //sensorValue = sensorValue / 1000;

  //pinMode(led, OUTPUT); // *** moved this to the setup. ***

 

 

// *** removed below and changed the if statement since we set switchState to D2 in the declarations ****

  //switchState = digitalRead(2);

 

  if (digitalRead(switchState) == HIGH)

  {

      // *********

      digitalWrite(led, HIGH);    //shows switchstate is HIGH *****

 

      FinalWt = (analogRead(0) - TareValue);

      //int FinalWt = 100 - 25;

      // print the results to the serial monitor:

      Serial.println(FinalWt);

      Serial.print(analogRead(0));

      Serial.print(" weight = " );

 

     // *** This is a value that has had some calculations but not had the Tare/Zero removed. ****

      Serial.print(sensorValue);

      // perhaps the value here should be FinalWt with the necessary calculations performed.

 

      Serial.print(" lbs/oz");

      ///Serial.print(" K/g");

      Serial.println ();

    //  digitalWrite(led, HIGH);

    //  delay(100);               // wait for a 100ms  ****** You might want to increase this as its a very short duration ***

    //  digitalWrite(led, LOW);

 

      // wait 400ms before the next loop

      // for the analog-to-digital converter to settle

      // after the last reading:

      delay(400);

      digitalWrite(led, LOW); // shows the process is finished and is on for approx 400-410mS give or take. 

  }

}

I also changed the LED to be on for longer than 100mS, since you would struggle to see that pulse.

I noted that your calculations of the actual weight aren't done, and put that down to the troubles you were having.

I'm sure you can tidy that up when you start getting sensible readings.

I've done some stuff with reading the contents of SD cards, but not a lot with writing to them.

One thing to make sure is that strings end with a null character.

Often they write a zero onto it if the original data wasn't a string.

The example Datatlogger converts it to a string

int sensor = analogRead(analogPin);

dataString += String(sensor);

Currently you are just writing a generic string ...

It compiles but other than that I have no promises.

Give it a whirl and see if it resolves the problems.

Mark

Hi Mark,

Still the same I'm afraid, it still seems to be around the subtraction function, FinalWt = (AnalogRead(A0) - TareValue); I have monitored the function and the result

is always the same, the value of eg; A0 = 500 and the TarValue = 100 the FinalWt result = 500?

if I change the TareValue  to a Constant say 200 then the result = 300?

If I change the TareValue to (int TareValue) the code will not compile asking for "expected primary-expression before 'int' could this be the problem?

Regards,

Gordon

Gordon

That result is a different problem than the impression you gave from you first post.....

To prove the loadcell is working, try loading and running the example AnalogInOutSerial.

This should prove the connections are working as they should be, as it uses Ao.

As you change the weight, you should be seeing a change in the output.

Some details of the actual loadcell in use would also help complete the picture.

Changing int settings or the like is not the problem.

Look at Help-reference and int for an explanation on what it means.

Constant int is one that the program can't and doesn't change.

Without seeing the code, its hard to judge why its reporting that, but I suspect its an extra or missing bracket or semicolon.

A copy and paste of the output of the Serial Monitor might also help, as you already output the TareValue when the Tare/Zero button is pressed.

Can you confirm that you have a resistor from the pin to ground as shown in this http://arduino.cc/en/Tutorial/Button

If not the pin will be floating and could be either HIGH or LOW, which will also stuff up your Tare/Zero reading.

If pin 2 is floating the whole sketch should be cycling and the led flashing at about 2Hz rate.

Mark

Hi Mark,

Hurray, I have found the problem!! I needed to create a new register 'int ZeroVal' as shown. then later the subtraction worked!

I have improved the HMI monitor layout  and it looks great, all I need to do now is work on the send to the SD card.

If you don't mind I'll keep in touch, thanks again for your help.

Regards,

Gordon

 

int TareValue = analogRead(A0);

    ZeroVal = TareValue;

    Serial.print("Tare Value = ");

    Serial.println (TareValue);


____________________________________________

 

if (digitalRead(switchState) == HIGH)

  {

      // *********
     
      digitalWrite(led, HIGH);    //shows switchstate is HIGH *****
     
      FinalWt = (analogRead(0) - ZeroVal);
     
      Serial.print("Raw AnalogValue = ");
      Serial.println(analogRead(0));
    
      Serial.print ("RawVal-Tare = FinalWt = ");
      Serial.println(FinalWt);

      sensorValue = FinalWt / 4.26;(analogInPin);

      sensorValue = sensorValue / 16;

    
      Serial.print("(FinalWt/4.26) / 16 = weight = " ); 
     
      Serial.print(sensorValue);
          
      Serial.print(" lbs/oz");

Hi Mark,

The monitor screen looks like this,

Gordon

 

Initializing Card

Card Ready

 

Tare Value = 107

Raw Analog Value = 321

Raw Val – Tare = Final Wt = 214

(Final Wt / 4.26) / 16 = Weight = 3.14 lbs/oz

Hello J,Gordon.

You may want to a to put a little more polish on that output especially if other people are going to use the application.

(Final Wt / 4.26) / 16 = Weight = 3.14 lbs/oz

may possibly be of more value if the output displayed:

(Final Wt / 4.26) / 16 = Weight = 3.14 lbs =  3 lbs  2.24 oz

Just a thought.  Congrats on taming your Arduino.