Designing constant current and constant voltage source for single cell Li-ion battery charger (Part- 4/17)

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//Program to 

*Linear regulator single 3.7V Li-ion battery charger 

*Charges the battery in Constant Current(CC) with 60mA current and in Constant Voltage(CV) mode with 4.2V 

*/

/*IN/OUT Pin connection 

*Sense battery voltage - A0

*Sense resistor voltage - A1

*BJT for Switching state relay - 11

*BJT for isolation relay - 12

*CC mode LED - 9

*CV mode LED - 8

*Fully charged battery LED - 7

*/


// They're used to give names

// to the pins used:

#define analogInPin_V_bat A0    // Analog input pin at battery positive

#define analogInPin_I_bat A1    // Analog input pin at sense resistor

#define switch_pin 11           // switching state relay 

#define isolation_pin 12        // Isolation pin relay 

//#define PowerSupply 10        // PowerSupply relay 

#define CC_LED 9                // LED indication for cv mode 

#define CV_LED 8                // LED indication for cc mode

#define BAT_FULL_LED 7          // LED indication for FULLY CHARGE battery 

int Flag = 0;                   // variable to set CC and CV mode


/////function declaration

float senseVoltage(void);              // Battery Voltage sensing 

float senseCurrent(float);             // Charging current sensing


/////Function definition

/*

* Function Name - senseVoltage

* Function to read voltage of battery

* Input parameters - none

* Return - float

*/

float senseVoltage(){

///read analog voltage

int senseV_bat = analogRead(analogInPin_V_bat);

// map it to the range of the analog out:

float  V_bat =(senseV_bat/1024.0)*5.0;   

Serial.println("currentBatteryVoltage");

Serial.println(V_bat);

return(V_bat);

}



/*

* Function Name - senseCurrent

* Function to read charging current of battery

* Input parameters - float

* Return - float

*/

float senseCurrent(float currentBatteryVoltage){

///read analog voltage

float senseResistor = analogRead(analogInPin_I_bat);

// map it to the range of the analog out:

float  senseResistorVoltage =(senseResistor/1024.0)*5.0; 

float actualResistor_Voltage = (senseResistorVoltage-currentBatteryVoltage); 

////calculating current from voltage difference of sense resistor 

float I_bat = (actualResistor_Voltage)*1000;

//print at serial monitor

Serial.println("currentBatteryVoltage");

Serial.println(currentBatteryVoltage);

Serial.println("senseResistorVoltage");

Serial.println(senseResistorVoltage);

Serial.println("actualResistor_Voltage");

Serial.println(actualResistor_Voltage);

Serial.println("I_bat");

Serial.println(I_bat);

return(I_bat);

}


void setup() {

  // initialize serial communications at 9600 bps:

 Serial.begin(9600);

  /////////set IN/OUT pins

  pinMode(switch_pin,OUTPUT);

  pinMode(isolation_pin,OUTPUT);

  pinMode(CC_LED,OUTPUT);

  pinMode(CV_LED,OUTPUT);

  pinMode(BAT_FULL_LED,OUTPUT);

  

  //initially both relays are OFF

  digitalWrite(switch_pin,LOW);

  digitalWrite(isolation_pin,LOW);

}


void loop() {

uint8_t BatteryState=0 ;                         // Variable to keep track of battery state


//Every time eet these pin low

digitalWrite(isolation_pin,LOW);

digitalWrite(CC_LED,LOW);

digitalWrite(CV_LED,LOW);



//////////****read the analogvalues

  float batteryVoltage = senseVoltage();                 //return battery voltage

  float  batteryCurrent = senseCurrent(batteryVoltage);  // return battery charging current

 if(Flag == 1)

 {

  // After CC mode enter in CV mode

  BatteryState = 2;

  Flag = 0;}// Battery enter in CV mde after CC mode

  

 else if(Flag == 2){

  while(batteryVoltage>=4.0){

    batteryVoltage = senseVoltage(); 

    //check for when battery is removed or battery is discharged below 4V

    if(batteryVoltage <4){

    Flag = 0;

    digitalWrite(BAT_FULL_LED,LOW);

    break;}}}// battery fully charged scanning for battery removed or not

    

 else if(batteryVoltage < 3.0){

 //do nothing

  }// No Battery or bad battery,Ideal state


 else if(batteryVoltage<4.0 && batteryVoltage>3.0){

   digitalWrite(isolation_pin,LOW);

   BatteryState = 1;

   }//charge battery in CC MODE


 else if(batteryVoltage >= 4.0){

  BatteryState = 2;

  }//charge battery in CV MODE


  /////////////*****MODE SELECT****///////////

  switch(BatteryState){

    case 1: // CC MODE

    ///Switch ON CC mode LED and trigger relay 

    digitalWrite(isolation_pin,HIGH);         

    digitalWrite(switch_pin,HIGH);

    digitalWrite(CC_LED,HIGH);

    Serial.println("CC mode");

    //when battery voltage is in between 3V and 4V enter in while loop

    while(batteryVoltage <4.0 && batteryVoltage>=3.0){

    batteryVoltage = senseVoltage();

    

  //check for when battery is charging in CC mode

    if(batteryVoltage>=4.0){

    digitalWrite(isolation_pin,LOW);

    //delay to compensate switching time of relay with software

    delay(100);

    Flag = 1;

    digitalWrite(CC_LED,LOW);

    break;}

    //check for when battery is removed

    else if(batteryVoltage<3.0){   

    digitalWrite(isolation_pin,LOW);

    digitalWrite(switch_pin,LOW);

    digitalWrite(CC_LED,LOW);

    Serial.println("EXIT ");

     //delay to compensate switching time of relay with software

    delay(100);

    break;}

    }

    break;  /// exit case 1.

    

    case 2: // CV MODE

     ///Switch ON CV mode LED and trigger relay 

    digitalWrite(isolation_pin,HIGH);

    digitalWrite(CV_LED,HIGH);

    Serial.println("Cv mode");

  

    batteryVoltage = senseVoltage(); 

    //when battery voltage is in 4V enter in while loop

    while(batteryVoltage >=4.0 ){

    batteryVoltage = senseVoltage();

    batteryCurrent = senseCurrent(batteryVoltage);


     //check for when battery is charging in CV mode

    if(batteryCurrent < 10){

    digitalWrite(isolation_pin,LOW); 

    //delay to compensate switching time of relay with software

    delay(100); 

    digitalWrite(CV_LED,LOW);

    digitalWrite(BAT_FULL_LED,HIGH);

    Flag = 2;

    Serial.println("Battery charged");

    break;}

    //check for when battery is removed

    else if(batteryVoltage<3.0){

    digitalWrite(isolation_pin,LOW);  

    //delay to compensate switching time of relay with software

    delay(100); 

    digitalWrite(CV_LED,LOW); 

    break;}

  }

  break; /////end of switch case 2.

  }

}
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