Suggested Feature request - Good or bad cap based on LCM3 predicted values

[mockendon]

It would be super convenient if the meter displayed whether the capacitor was likely in specification for its measured capacitance.

The Table of Pudics István & Piri Dániel 2010 gives a suggested logarithmic scale for this (attached).

If we take the 63-100V line and find the equation of that line we can calculate that the upper limit for ESR is:

R = (C/81.303) ^(1/-1.085)

Where R is Ohms and C is in uF

Could we calculate this value on the fly and display a symbol to show 'good' or 'bad' as a guide?

[mockendon]

So I have implemented this (poorly, I can only apologise for adding my terrible hack to your elegant code) as a proof of concept by adding these lines to these sections. It displays either an 'OK' or an 'X' symbol after the ESR measurement. Modified .ino attached.

C_ESR_METER_modified.zip

#define OK    (byte)5                     // LCD custom char for OK character
#define BAD   (byte)6                     // LCD custom char for Bad character

 // OK character
byte ok[8] = {
  0b00000100,0b00001010,0b00001010,0b00000100,0b00001000,0b00001010,0b00001100,0b00001010
};

// Bad character
byte bad[8] = {
  0b00000000,0b00010001,0b00001010,0b00000100,0b00001010,0b00010001,0b00000000,0b00000000
}; 
  
// --------------------- Global vars --------------------- 
bool CapOK                = false;        // True if ESR less than predicted


  // Init LCD
  lcd.init();
  lcd.createChar(SKIP,  skip);    // Skip address 0x00
  lcd.createChar(OMEGA, omega);   // "Ω" Omega      \1
  lcd.createChar(MU,    mu);      // "µ" Mu (micro) \2
  lcd.createChar(BELL,  bell);    // bell           \3
  lcd.createChar(LOCK,  lock);    // lock           \4
  lcd.createChar(OK,  ok);        // ok             \5
  lcd.createChar(BAD,  bad);      // bad            \6
  
// Get Cx measure
// Receives ESR measure to passthrough it to Cx meter function
// Returns Cx (µF) or any negative value when timeout 


float predESR = pow((Cx/81.303),1 / -1.085);
if (predESR > esr){CapOK = true;}else{CapOK = false;}



// -------------------- Display Functions ------------------

// Display ESR (Ω) Ohms normal "ESR run mode"

  // Display good or bad symbol
  lcd.setCursor(15,1);              // Display to last position LCD second line
  if(CapOK == true){
    lcd.print(F("\5 ")); // "OK"
  }else{
    lcd.print(F("\6 ")); // "X"
  }

[latchdevel]

Hi,

The approach you describe is very good, although it's difficult to determine the correct values.

The ESR of capacitors is greatly influenced by temperature and measurement frequency, and only the manufacturer can specify the correct value.

Some manufacturers provide detailed information, so much so that even for the same capacitor with the same capacitance and voltage, the ESR varies depending on its size.

If it works for you, great!; this is the advantage of open source.

Although I would recommend a more appropriate use of Git and GitHub to facilitate sharing your proposals: clone the repository, create a branch, commit your changes, and make a pull request if you want.

In any case, I'll think about this for a few days to find the best way to integrate this feature.

Best regards.