A class to Measure the Battery

• Hi all, for the sake of beginners like myself and to get advice on it, here is the code i have done to measure the battery of my sensors

based on @sundberg84 here: EasyNewbie-PCB-for-MySensors and articles i've read here

Here is the class definition:

``````class MyBM {
public:
MyBM();
MyBM(const float _VMIN, const float _VMAX);
void setup(void);
void MeasureBattery(void); //The battery calculations
private:
float VBAT_PER_BITS;
float VMIN;                          //  Vmin (radio Min Volt)=1.9V (564v)
float VMAX;                          //  Vmax = (2xAA bat)=3.0V (892v)
int batteryPcnt = 0;                 // Calc value for battery %
int batLoop = 0;                     // Loop to help calc average
int batArray[3];                     // Array to store value for average calc.
unsigned int BATTERY_SENSE_PIN = A0; // select the input pin for the battery sense point
int sValue;
float Vbat;
};
``````

You can change the values in the constructor MyBM() ; by default it is the resistors 1M and 470k for EasyPCB.

Following advice found on stackoverflow, i make 8 readings in burnreadings() when switching from analogReference(INTERNAL) to analogReference(DEFAULT) back & forth

``````MyBM::MyBM() {
this->VMIN= 2.0 ;                   //  Vmin (radio Min Volt)=1.9V (564v)
this->VMAX= 3.3;                    //  Vmax = (2xAA bat)=3.0V (892v)
this->VBAT_PER_BITS= (1470/470)*(1.1/1024);
}

MyBM::MyBM(const float _VMIN, const float _VMAX) {
MyBM();
this->VMIN= _VMIN;
this->VMAX= _VMAX;
}

{
for (int i = 0; i < 8; i++)
{
}
}

void MyBM::setup(void) {
//=========================
// BATTERY MEASURER

//DEFAULT: the default analog reference of 5 volts (on 5V Arduino boards) or 3.3 volts (on 3.3V Arduino boards)
//INTERNAL: an built-in reference, equal to 1.1 volts on the ATmega168 or ATmega328 and 2.56 volts on the ATmega8 (not available on the Arduino Mega)
//EXTERNAL: the voltage applied to the AREF pin (0 to 5V only) is used as the reference.

analogReference(INTERNAL);    // set the ADC reference to 1.1V
delay(10);                    // idle some time

//Battery inital calc
DPR("With Battery VMax (100%) = "); DPR(VMAX); DPR("volts and Vmin (0%) = "); DPR(VMIN); DPRLN(" volts");
DPR("Battery Percent 25%/50%/75% calculates to: "); DPR(((VMAX - VMIN) / 4) + VMIN); DPR("/"); DPR(((VMAX - VMIN) / 2) + VMIN); DPR("/"); DPRLN(VMAX - ((VMAX - VMIN) / 4));
DPR("Batterysens :"); DPRLN(sValue);
Vbat  = sValue * VBAT_PER_BITS;
batteryPcnt = static_cast<int>(((Vbat - VMIN) / (VMAX - VMIN)) * 100.);
DPR("Current battery are measured to (please confirm!): "); DPR(batteryPcnt); DPR(" % - Or "); DPRLN(Vbat); DPRLN(" Volts");

analogReference(DEFAULT);     // set the ADC reference back to internal
delay(10);                    // idle again

//=========================
}

void MyBM::MeasureBattery() {
analogReference(INTERNAL);    // set the ADC reference to 1.1V
delay(10);                    // idle some time

DPR("Batterysens :"); DPRLN(sValue);
//delay(500);

// Calculate the battery in %
Vbat  = sValue * VBAT_PER_BITS;
batteryPcnt = static_cast<int>(((Vbat - VMIN) / (VMAX - VMIN)) * 100.);

DPR("Battery percent: "); DPR(batteryPcnt); DPR(" %"); DPR("Battery Voltage: "); DPR(Vbat); DPRLN(" Volts");

// Add it to array so we get an average of 3 (3x20min)
batArray[batLoop] = batteryPcnt;

if (batLoop > 2) {
batteryPcnt = (batArray[0] + batArray[1] + batArray[2]);
batteryPcnt = batteryPcnt / 3;

if (batteryPcnt > 100) {
batteryPcnt = 100;
}
DPR("Battery Average (Send): "); DPR(batteryPcnt); DPRLN(" %");
sendBatteryLevel(batteryPcnt);
batLoop = 0;
}
else
{
batLoop++;
}

analogReference(DEFAULT);     // set the ADC reference back to internal
delay(10);                    // idle again
}
``````

Here is how i use it with a sensor that manages both interrupts and a sensor-specific timeout

``````// sdj is an object representing the sensor
MyBM bm;

void setup()
{
sdj.setup();
bm.setup();
}

void loop()
{
if (tripped==0) {
the_switch= sdj.get();
} else if (tripped==MY_WAKE_UP_BY_TIMER) {
if (sdj.wait_next()) {
// timeout needs to do something for the sensor
sdj.resetCode();
} else {
// timeout , nothing occured for sensor
bm.MeasureBattery();
}
}

// Sleep until something happens with the sensor or timeout
tripped= sdj.sleep(WAIT_LOOP);
}

``````

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