Switching mechanism for linear regulator single cell Li-ion battery charger using microcontroller and relay (Part -5/17)

Maximum current that has to flow from the resistor R_sense is 60mA.

So, Power =(maximum current across R_sense)²*R_sense

Power = (0.06*0.06)*1

Power = 3.6 mW

So as per the availability, a resistor having power rating of 0.25 W can be used for R_sense. The current sense resistor is interfaced to the pin A1 of the Arduino while the pin A0 of the Arduino is interfaced to the output terminals of the charger circuit for sensing the battery voltage.

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//Program to 
 Author - Diksha
 *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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