Hi Gil(?).
Thanks for your reply, but I do have some questions if I may. Please see code at the end of this reply.
I'm using an Nano, 3.3V unit. I'm supplying external power from an adapter (5.15V).
The arduino is being powered via the "RAW" pin and "GND".
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Am I correct in saying that the LM385 is used as a constant reference voltage (read in pin A1 - Vref_Pin - line 94)?
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Is it correct to have only 2 pins of the voltage reference connected - Pin 1 & 2?
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The voltage across GND and this Pin 2 is 3.90V. It that what it should be? How can I check?
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You mentioned the ground of R3 should also be connected to DUT ground. I've connected all grounds together (including the battery). Is that correct?
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I measured the Gate voltage without a battery as you suggested. It's 4.12V. With the battery, it's 1.816V. When connected and running, it measures 1.920V at the lowest mA setting and 4.12V at the highest mA setting.
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Your suggestion for protection of the A0 pin? Is this a 10K as Wawa noted? Do I connect it btwn GND and pin A0?
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Lastly, I don't get what line 31 to 33 in the code are doing - how they are adjusting the current/PWM values. When I toggle with SW2 button, it goes from Curr = 51mA & PWM=3 to Curr = 103mA & PWM=7, up to Curr = 999mA and PWM=76. I assume that 76 is the "duty cycle" ranging from 0 to 255?
If I have a AA NiMh that is 2800mA, should I be discharging it at 280mA (1/10 capacity)? If I discharge it faster or slower, would the capacity read about the same? What if I then connect my 10,000mA D size batteries. What discharge should these use?
Sorry for the zillion questions. I'm a bit of a newby here and wanting to make sure this is accurate. My long term is to build one of these for each of my 4 kids as well as an inbuilt charger to handle 4 AA's. I'd also like the unit to display the internal resistance of the battery to show if their still ok.
//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
// ARDUINO BATTERY CAPACITY TESTER
//Version-2.1
//by deba168,INDIA // The code is taken from Hesam Moshiri ( https://www.pcbway.com/blog/technology/Battery_capacity_measurement_using_Arduino.html )
//Dated : 02/02/2022
//
//Dated : 29/02/2020
//Added code to read a band gap reference connected to analog pin A1,
// thus allowing measurement of Vcc and avoiding the need to measure it using a multimeter
//Replaced 1 ohm 5% resistor with 1 ohm 1% power resistor
//Modified code to compute actual current draw based on desired values. Measurements
// using ammeter show computed values within 2 milliamps of measured
//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
#include<JC_Button.h>
#include <Adafruit_SSD1306.h>
#define DEBUG 0 // Binary Treatment 0=Nothing, 1=Early, 2=Running Voltages, 4=Finish
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET 4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
void timerInterrupt();
void Display_UP_DOWN();//Debugging support
void Print_DEBUG_4();//Debugging support
const float Low_BAT_level = 0.90;// Threshold for stopping test
int Current [] = {0, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000};
int PWM [] = {0, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50};
int Array_Size;// calculated during setup
const byte PWM_Pin = 10;
const byte Buzzer = 9;
const int BAT_Pin = A0;
const int Vref_Pin = A1;//Pin to which Band Gap Reference is attached
int Current_Value = 0; // Selected Current value for test
int PWM_Value = 0;// Value of PWM during test
int PWM_Index = 0;// Index into PWM array during test
unsigned long Capacity;
float Capacity_f;
int ADC_Value = 0;
float Vref_Voltage = 3.32; // LM385BLP-1.2 Band Gap Reference voltage
float Vcc = 5.14; // Voltage of Arduino 5V pin ( Measured during setup using Band Gap Reference )
float BAT_Voltage = 0;
float Resistance = 1.0; // Value of R3 Power Resistor
float sample = 0;
byte Hour = 0, Minute = 0, Second = 0;
bool calc = false, Done = false, Report_Info = true;
Button UP_Button(2, 25, false, true);
Button Down_Button(3, 25, false, true);
// string values for reporting intermediate information
const int VAL_MAX = 10;
char val_0[VAL_MAX] = {""};
char val_2[VAL_MAX] = {""};
void setup () {//Setup
Serial.begin(38400);
pinMode(PWM_Pin, OUTPUT);
pinMode(Buzzer, OUTPUT);
analogWrite(PWM_Pin, PWM_Value);
UP_Button.begin();
Down_Button.begin();
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
display.clearDisplay();
display.setTextColor(WHITE);
display.setTextSize(1);
display.setCursor(12, 25);
display.print("Open Green Energy");
display.display();
delay(3000);
display.clearDisplay();
display.setTextSize(2);
display.setCursor(2, 15);
display.print("Adj Curr:");
display.setCursor(2, 40);
display.print("UP/Down:");
display.print("0");
display.setCursor(2, 55);
display.setTextSize(1);
#if (DEBUG == 1 || DEBUG == 5)
Serial.println("\nStart of calculations");
#endif
Array_Size = sizeof(Current) / 2;
//Read voltages of Band Gap Reference and use it to calculate actual Vcc
float fTemp = 0.0;
for (int i = 0; i < 100; i++)
{
fTemp = fTemp + analogRead(Vref_Pin); //read the Band Gap Reference voltage
delay (2);
}
fTemp = fTemp / 100.0;
Vcc = Vref_Voltage * 1024.0 / fTemp;
// Convert desired current levels to PWM using actual Vcc
// Convert PWM values back to actual current levels
// While measuring actual current I discovered that the actual draw is
// (PWM + 1)/256 rather than PWM/255 as indicated in Arduino documentation
int iTemp;
for (int i = 0; i < Array_Size; i++)
{
iTemp = int( Resistance * Current[i] * 256.0 / Vcc / 1000.0 - 1.0 + 0.5 ); // desired current to nearest PWM
iTemp = min(iTemp, 255);
iTemp = max(iTemp, 0);
Current[i] = int( (iTemp + 1) * Vcc / 256.0 / Resistance * 1000.0); // actual current for PWM
PWM[i] = iTemp;//Save PWM in array
}
//Include Threshold and Vcc in startup display
dtostrf(Low_BAT_level, 5, 3, val_0);
dtostrf(Vcc, 5, 3, val_2);
display.print("Thr=");
display.print(val_0);
display.print("v, Vcc=");
display.print(val_2);
display.display();
display.setTextSize(2);
}//Setup
//************************* End of Setup function *******************************
void loop() {
if (Report_Info)
{ //Report_Info
Serial.flush();
#if (DEBUG == 1 || DEBUG == 5)
// Serial.println("Measured Vcc Voltage: " + String(Vcc) + " volts");
Serial.print("Threshold: ");
Serial.print(Low_BAT_level, 3);
Serial.println(" volts");
Serial.print("R3 Resistance: ");
Serial.print(Resistance, 3);
Serial.println(" ohms");
Serial.print("Measured Vcc Voltage: ");
Serial.print(Vcc, 4);
Serial.println(" volts");
sample = 0.0;
Serial.println("Index Actual(mA) PWM");
for (int i = 0; i < Array_Size; i++)
{
// Serial.println( "["+String(i)+"]="+String(Current[i])+" mA PWM["+String(i)+"]="+String(PWM[i]) );
Serial.print("[");
Serial.print(i);
Serial.print("]");
Serial.print(" ");
Serial.print(Current[i], DEC);
Serial.print(" ");
Serial.print(PWM[i], DEC);
Serial.println(" ");
}
#endif
Report_Info = false;
}//Report_Info
UP_Button.read();
Down_Button.read();
if (UP_Button.wasReleased() && PWM_Index < (Array_Size - 1) && calc == false)
{
PWM_Value = PWM[++PWM_Index];
analogWrite(PWM_Pin, PWM_Value);
Display_UP_DOWN();
}
if (Down_Button.wasReleased() && PWM_Index > 0 && calc == false)
{
PWM_Value = PWM[--PWM_Index];
analogWrite(PWM_Pin, PWM_Value);
Display_UP_DOWN();
}
if (UP_Button.pressedFor (1000) && calc == false)
{
digitalWrite(Buzzer, HIGH);
delay(100);
digitalWrite(Buzzer, LOW);
display.clearDisplay();
timerInterrupt();
}
}
//************************* End of Loop function *******************************
void timerInterrupt() {
calc = true;
while (Done == false) {//(Done == false)
Second ++;
if (Second == 60) {
Second = 0;
Minute ++;
}
if (Minute == 60) {
Minute = 0;
Hour ++;
}
//************ Measuring Battery Voltage ***********
for (int i = 0; i < 100; i++)
{
sample = sample + analogRead(BAT_Pin); //read the Battery voltage
delay (2);
}
sample = sample / 100;
BAT_Voltage = sample * Vcc / 1024.0;
Serial.print("BAT_Pin = ");
Serial.print(BAT_Pin, 3);
Serial.print(", Vref_Voltage = ");
Serial.print(Vref_Voltage, 3);
Serial.print(", sample = ");
Serial.print(sample, 3);
Serial.print(", Vcc = ");
Serial.print(Vcc, 3);
Serial.print(", BAT_Voltage = ");
Serial.println(BAT_Voltage, 3);
// Vcc = Vref_Voltage * 1024.0 / fTemp;
//*********************************************
display.clearDisplay();
display.setTextSize(2);
display.setCursor(20, 5);
// display.print(String(Hour) + ":" + String(Minute) + ":" + String(Second));
display.print(Hour);
display.print(":");
display.print(Minute);
display.print(":");
display.print(Second);
display.setTextSize(1);
display.setCursor(0, 25);
display.print("Disch Curr: ");
// display.print(String(Current[PWM_Index])+"mA");
display.print(Current_Value);
display.print("mA");
display.setCursor(2, 40);
// display.print("Bat Volt:" + String(BAT_Voltage)+"V" );
display.print("Bat Volt:");
display.print(BAT_Voltage, 3);
display.print("V");
// When total seconds is greater than 32767 the statement below did not work until the byte values
// Hour, Minute and Second were cast to an unsigned long. Apparently the compiler cast the byte
// values to an "int" first which cannot represent 32768 correctly
Capacity = ((unsigned long)Hour * 3600) + ((unsigned long)Minute * 60) + (unsigned long)Second;
Capacity_f = ((float)Capacity * Current_Value) / 3600.0;
display.setCursor(2, 55);
// display.print("Capacity:" + String(Capacity) + "mAh");
display.print("Capacity:");
display.print(Capacity_f, 0);
display.print("mAh");
display.display();
#if (DEBUG == 4 || DEBUG == 2)
Print_DEBUG_4();
#endif
if (BAT_Voltage < Low_BAT_level)
{ //BAT_Voltage < Low_BAT_level
#if (DEBUG == 4 || DEBUG == 5)
Serial.println("\nCurrent_Value PWM_Value");
Serial.print(Current_Value);
Serial.print(" ");
Serial.println(PWM_Value);
Serial.println("\nHour Minute Second PWM_Index");
Serial.print(Hour);
Serial.print(" ");
Serial.print(Minute);
Serial.print(" ");
Serial.print(Second);
Serial.print(" ");
Serial.println(PWM_Index);
#endif
// When total seconds is greater than 32767 the statement below did not work until the byte values
// Hour, Minute and Second were cast to an unsigned long. Apparently the compiler cast the byte
// values to an "int" first which cannot represent 32768 correctly
Capacity = ((unsigned long)Hour * 3600) + ((unsigned long)Minute * 60) + (unsigned long)Second;
#if (DEBUG == 4 || DEBUG == 5)
Serial.println("Capacity HMS");
Serial.println(Capacity);
#endif
Capacity_f = ((float)Capacity * Current_Value) / 3600.0;
#if (DEBUG == 4 || DEBUG == 5)
Serial.println("Capacity HMS*PWM");
Serial.println(Capacity_f, 1);
#endif
display.clearDisplay();
display.setTextSize(2);
display.setCursor(2, 15);
display.print("Capacity:");
display.setCursor(2, 40);
// display.print(String(Capacity) + "mAh");
display.print(Capacity_f, 1);
display.print("mAh");
display.display();
Done = true;
PWM_Value = 0;
analogWrite(PWM_Pin, PWM_Value);
digitalWrite(Buzzer, HIGH);
delay(200);
digitalWrite(Buzzer, LOW);
delay(100);
digitalWrite(Buzzer, HIGH);
delay(200);
digitalWrite(Buzzer, LOW);
delay(100);
digitalWrite(Buzzer, HIGH);
delay(200);
digitalWrite(Buzzer, LOW);
delay(100);
digitalWrite(Buzzer, HIGH);
delay(200);
digitalWrite(Buzzer, LOW);
delay(100);
digitalWrite(Buzzer, HIGH);
delay(200);
digitalWrite(Buzzer, LOW);
delay(100);
}//BAT_Voltage < Low_BAT_level
delay(1000);
}//(Done == false)
}// timerInterrupt
void Display_UP_DOWN()
{ //Display_UP_DOWN()
Current_Value = Current[PWM_Index];
display.clearDisplay();
display.setCursor(2, 25);
display.print("Curr:");
display.print(Current_Value);
display.print("mA ");
display.setCursor(2, 40);
display.print("PWM=");
display.print(PWM_Value);
display.display();
}//Display_UP_DOWN()
void Print_DEBUG_4()
{ //Print_DEBUG_4()
Serial.print(Hour);
Serial.print(":");
Serial.print(Minute);
Serial.print(":");
Serial.print(Second);
Serial.print(" ");
Serial.print(BAT_Voltage, 3);
Serial.print("v ");
Serial.print(Capacity_f, 1);
Serial.println("mAh");
}//Print_DEBUG_4()
