Analog input 'Tare/Zero' Weight Function

Gordon

Without seeing your code I can't offer the exact code but something along these lines should work.

Detect 'zero' button

Read analog and store in a variable (ie int ZeroValue = 0; // value to store zero reading)

Whenever you read the load cell, you subtract the ZeroValue from the reading

Detect the 'monitor' button

display or print the ZeroValue rather than the load cell reading

This will remain until the micro is reset, either by power, reset button or upload.

Good luck

Mark

Hi Mark,

Thank you for your early feedback, you described it exactly how I would do it in PLC terms, I am new to Arduino so I am struggling with the code structure, I feel your suggestion will work, I will need to trial a few sketches and then import the working code into my current project.

Best wishes,

Gordon

int loadCellPin = 1;

int tareButtonPin = 8;

int currentWeight = 0;

int taredWeight = 0;

void loop() {

  //do some math to convert anaglogRead(loadCellPin) to a weight

  currentWeight = //results of that math;

  //check if the tare button is pushed, to see if it needs to store a value.

  if (digitalRead(tareButtonPin) == HIGH) {

    taredAmt = anaglogRead(loadCellPin);

  }

  //do the math to convert taredWeight from 0-1023 to a weight

  //i assume you'll have some sort of lcd code setup

  lcd.print("Weight: ");

  lcd.print(currentWeight - taredWeight);

}

This is what you need on a very basic level, but without any specifics I cant help too much more.

Hi,

Thanks for the assistance, I would like to send my code to you to check it over, I am only a beginner and it has been trial and error so far.

Basically I want to store a weight to an SD card shield which I have setup ok, but the tare function has stumped me!

I have 2 buttons, button 1 is the Tare/Zero, Button 2 is the 'take weigh sample' button.

I have setup to write to monitor and I can display the Tare weight when button 1 is pressed, when Button 2 is pressed it displays a scaled value in Pounds/Ounces, my problem is I cant get the subtraction of the Tare weight to work.

I would appreciate any help you could give me.

How can I send you the code?

Regards,

Gordon

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?

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