Thermocouple and multimeter

Question

I've put together this script that should allow my Arduino Mega to be show thermocouple readings on the serial monitor, whilst also showing readings of voltage and ohms across a given component. I'd be grateful for any advice on how it can be improved/streamlined:

#include <SparkFun_MCP9600.h>
MCP9600 tempSensor;
int analogPin = 0;
int raw = 0;
int Vin = 5;
float Vout = 0;
float R1 = 220;
float R2 = 0;
float buffer = 0;
float volt = 0;
int input = 0;

void setup() {
  Serial.begin(115200);
  Wire.begin();
  Wire.setClock(100000);
  tempSensor.begin();

  if (tempSensor.isConnected()) {
    Serial.println("Device will acknowledge!");
  }
  else {
    Serial.println("Device did not acknowledge! Freezing.");
    while (1); //hang forever
  }

  if (tempSensor.checkDeviceID()) {
    Serial.println("Device ID is correct!");
  }
  else {
    Serial.println("Device ID is not correct! Freezing.");
    while (1);
  }

  pinMode(A4, INPUT);
}

void loop() {

  input = analogRead(A4); //analogRead function is used to receive analog data
  volt = (input * 5.0) / 1024.0; //formula using for perform action

  if (tempSensor.available()) {
    Serial.print("Thermocouple: ");
    Serial.print(tempSensor.getThermocoupleTemp());
    Serial.print(" °C   Ambient: ");
    Serial.print(tempSensor.getAmbientTemp());
    Serial.print(" °C   Temperature Delta: ");
    Serial.print(tempSensor.getTempDelta());
    Serial.print(" °C");
    Serial.println();
  }

  raw = analogRead(analogPin);
  if (raw)
  {
    buffer = raw * Vin;
    Vout = (buffer) / 1024.0;
    buffer = (Vin / Vout) - 1;
    R2 = R1 * buffer;
    Serial.print("Vout: ");
    Serial.println(Vout);
    Serial.print("R2: ");
    Serial.println(R2);
    Serial.print("voltage is:");
    Serial.println(volt);
    Serial.print("current is:");
    Serial.println(volt / R2);
    delay(1000);
  }
}

Thomas Weller · Answer 1 · 2020-02-15T16:07:44.387

Your code is not very long, but I already see a few things that I would change.

int analogPin = 0;
[...]
pinMode(A4, INPUT);

These usages of pins are inconsistent. I personally prefer settings at the beginning of the file, so I'd expect

int analogPin = 0;
int whateverPin = A4;  // I don't have a good name yet

While you have

pinMode(A4, INPUT);

there's no

pinMode(analogPin, INPUT);

The main loop is doing 2 things: a) show temperature reading and b) show the component specs. This would be more obvious if written like this:

void loop() {
  input = analogRead(A4); //analogRead function is used to receive analog data
  volt = (input * 5.0) / 1024.0; //formula using for perform action

  showTemperatureReadings();
  showComponentReadings();    
}

Now, that looks a bit strange, don't you think? What about the stuff before these two big show...() methods? These two lines clearly belong into showComponentReadings().

Now, a lot of variables are declared outside of methods. This makes them global variables. It's possible to change them from anywhere in the code. When the project grows, side effects are evil. Let's remove as many of them as possible.

You can get rid of:

int input = 0;
float volt = 0;
float buffer = 0;
float R2 = 0;
float Vout = 0;
int raw = 0;

After this change, I think the setup() method could be more concise. A lot of stuff just deals with the temperature sensor. I would extract a method as well.

The error messages like

Device did not acknowledge! Freezing.

could not mean very much to the user. A message like

Temperature sensor did not acknowledge! Check the wiring and press the reset button to retry.

could give more meaningful instructions.

The final code with these suggestions applied:

#include <SparkFun_MCP9600.h>
MCP9600 tempSensor;
int analogPin = 0;
int whateverPin = A4;
float R1 = 220;
int Vin = 5;

void setupTemperatureSensor() {
  tempSensor.begin();
  if (tempSensor.isConnected()) {
    Serial.println("Temperature sensor acknowledged.");
  }
  else {
    Serial.println("Temperature sensor did not acknowledge! Check the wiring and press the reset button to retry.");
    while (1); //hang forever
  }

  if (tempSensor.checkDeviceID()) {
    Serial.println("Temperature sensor ID is correct.");
  }
  else {
    Serial.println("The temperature sensor ID does not have the expected value. Do you use a different sensor type? Use a SparkFun MCP9600.");
    while (1);
  }
}

void setup() {
  Serial.begin(115200);
  Wire.begin();
  Wire.setClock(100000);

  setupTemperatureSensor();

  pinMode(whateverPin, INPUT);
  pinMode(analogPin, INPUT);
}

void showTemperatureReadings() {
    if (tempSensor.available()) {
    Serial.print("Thermocouple: ");
    Serial.print(tempSensor.getThermocoupleTemp());
    Serial.print(" °C   Ambient: ");
    Serial.print(tempSensor.getAmbientTemp());
    Serial.print(" °C   Temperature Delta: ");
    Serial.print(tempSensor.getTempDelta());
    Serial.print(" °C");
    Serial.println();
  }
}

void showComponentReadings() {
  int input = analogRead(whateverPin); //analogRead function is used to receive analog data
  float volt = (input * 5.0) / 1024.0; //formula using for perform action
  int raw = analogRead(analogPin);
  if (raw)
  {
    float buffer = raw * Vin;
    float Vout = (buffer) / 1024.0;
    buffer = (Vin / Vout) - 1;    
    float R2 = R1 * buffer;
    Serial.print("Vout: ");
    Serial.println(Vout);
    Serial.print("R2: ");
    Serial.println(R2);
    Serial.print("voltage is:");
    Serial.println(volt);
    Serial.print("current is:");
    Serial.println(volt / R2);
    delay(1000);
  }
}

void loop() {
  showTemperatureReadings();
  showComponentReadings();
}

With code folding active, I'd say it's now very simple to get an overview of what the code is doing and what can be configured:

Edit:

After you linked to the schematics, I would

rename whateverPin to voltageDividerPin.
change the calculation float volt = (input * 5.0) / 1024.0; to a mapping, because it maps the 1024 input values to 5V, so float volt = map(voltageReading, 0, 1024, 0, Vin);
remove analogPin completely, because it's not used in the original code as well.

I also hope that read the article and you understood the consequences of using a 220 Ohm resistor.

Thermocouple and multimeter

1 Answers1