Unknown battery drain

[iahim67]

@Richard-van-der-Plas - you can use any Arduino Mini or Mini Pro for a battery powered sensor.
It does not matter much if you buy a 5V or a 3V3 Mini Pro version as you will better flash an internal 8MHz bootloader, remove the linear voltage regulator on these boards and the LED or LEDs as well. I use battery powered temperature sensors (with thermistors)since November 2017 and they still work fine -> I use 2xR6 batteries. Things you can do (like I did, after lots of reading on this forum):

• important! remove the LDO (the low drop output voltage regulator) equipped on the Arduinos
• remove the LED or LEDs
• flash an 8MHz internal oscillator bootloader (I read in this forum that using 1MHz internal osc. may give you occasional faults, don't know if that is still valid!) - do you know how to do that?
• internal 8MHz could be precise enough to work with your Dallas temperature sensors, I'm not sure without checking the datasheet
• an 8MHz Arduino (ATMega328P in this case) can work down to about 2V4 according to the datasheet, while the radio works down to 1V9
• either use 2 x R6 batteries to power both the Arduino and the radio module
• or use 3 xR6 batteries to power the Arduino BUT (important!) get power for the radio only from two of the R6 batteries or you'll damage it
• I bought battery powered Christmas lights from LIDL and Kaufland, they had very cheap Christmas lights with both 2 and 3 R6 batteries - so I just use the very convenient battery plastic housing equipped with an ON/OFF switch. Or just look for some R6 or AAA battery holders ...
• make sure you connect the Ground of both the Arduino and the Radio to the "-" of the battery string
• NiMH rechargeable batteries have a much higher self discharge rate than alkaline non rechargeable batteries, NiMH would not be a good option to me as I would have to replace them quite often, but may fit your needs:-)
• ATMega328P can measure its internal 1V1 reference and by doing that you can calculate the battery voltage without a resistor divider that would drain a few more uA, use this library:
  https://forum.mysensors.org/topic/186/new-library-to-read-arduino-vcc-supply-level-without-resistors-for-battery-powered-sensor-nodes-that-do-not-use-a-voltage-regulator-but-connect-directly-to-the-batteries
• you can use thermistors to measure the temperature as they are very cheap and most important - you can power the thermistor from an Arduino pin by making it an OUTPUT and set it HIGH. After reading the temperature set it back to LOW and put the Arduino to sleep. You will conserve even more power this way. Hope it helps ...
• forgot to clarify, you are supposed to connect the "+" of the battery string to the 5V pin header on the Arduino (there are 2 such pins I think), not to the RAW pin header. 5V can be anything between 2V4 and 5V (for an 8MHz Arduino) and goes directly to the ATMega VCC pin while RAW connector goes to the input of the Linear Voltage Regulator you are supposed to remove
• while looking to your code I can see you have many delay() lines which means your Arduino is awake for many seconds, that's just not good enough for a battery powered sensor :-), try to remove these delays as much as possible, use different sensors that do not require delays eventually as the Arduino should be mostly sleeping. Use eventually a #define DEBUG x statement (x=1 if you like to have a serial debug output or x=0 if you don't) and only output the Serial.print when needed.Here is an example for a temperature sensor with a thermistor and 2xR6 batteries (not using here the VCC library I mentioned before but something similar):

// Enable debug prints to serial monitor
//#define MY_DEBUG

#define MY_RADIO_NRF24
#define MY_NODE_ID 10
#define DEBUG 0
#define BATTERY_SENSOR 1

#include <MySensors.h>

#define TH1_CHILD_ID 11
#define VOLTAGE_CHILD_ID 12
#define TH_PIN 3

int _nominal_resistor = 4700;
int _nominal_temperature = 25;
int _b_coefficient = 3950;
int _series_resistor = 4877;
int _pin = 0;

float BatteryMin = 2.4;
float BatteryMax = 3.0;

MyMessage msgTemp(TH1_CHILD_ID, V_TEMP);
MyMessage msgVoltage(VOLTAGE_CHILD_ID, V_VOLTAGE);

void setup()
{
  //Serial.begin(115200);
}

void presentation()
{
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("TH1_Mini_2xR6", "1.0");
  present(TH1_CHILD_ID, S_TEMP, "TH1");
  present(VOLTAGE_CHILD_ID, S_MULTIMETER, "TH1_Batt_Voltage");
}

void loop()
{
  tempReport();
  batteryReport();
  sleep(180000);
}

// Measure VCC
float getVcc() {
#ifndef MY_GATEWAY_ESP8266
  // Measure Vcc against 1.1V Vref
#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
  ADMUX = (_BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1));
#elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
  ADMUX = (_BV(MUX5) | _BV(MUX0));
#elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
  ADMUX = (_BV(MUX3) | _BV(MUX2));
#else
  ADMUX = (_BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1));
#endif
  // Vref settle
  wait(70);
  // Do conversion
  ADCSRA |= _BV(ADSC);
  while (bit_is_set(ADCSRA, ADSC)) {};
  // return Vcc in mV
  return (float)((1125300UL) / ADC) / 1000;
#else
  return (float)0;
#endif
}

// Send a battery level report to the controller
void batteryReport() {
  // measure the board vcc
  float volt = getVcc();
  // calculate the percentage
  int percentage = ((volt - BatteryMin) / (BatteryMax - BatteryMin)) * 100;
  if (percentage > 100) percentage = 100;
  if (percentage < 0) percentage = 0;
#if DEBUG == 1
  Serial.print(F("BATT V="));
  Serial.print(volt);
  Serial.print(F(" P="));
  Serial.println(percentage);
#endif
#if BATTERY_SENSOR == 1
  // report battery voltage
  send(msgVoltage.set(volt, 3));
#endif
  // report battery level percentage
  sendBatteryLevel(percentage);
}

void tempReport()
{
  // set TH pin in output mode
  pinMode(TH_PIN, OUTPUT);
  // set TH_PIN HIGH
  digitalWrite(TH_PIN, HIGH);
  wait(1);
  // read the voltage across the thermistor
  float adc = analogRead(_pin);
  // set TH_PIN LOW
  digitalWrite(TH_PIN, LOW);
  // calculate the temperature
  float reading = (1023 / adc)  - 1;
  reading = _series_resistor / reading;
  float temperature;
  temperature = reading / _nominal_resistor;     // (R/Ro)
  temperature = log(temperature);                  // ln(R/Ro)
  temperature /= _b_coefficient;                   // 1/B * ln(R/Ro)
  temperature += 1.0 / (_nominal_temperature + 273.15); // + (1/To)
  temperature = 1.0 / temperature;                 // Invert
  temperature -= 273.15;                         // convert to C
#if DEBUG == 1
  Serial.print(F("THER I="));
  Serial.print(TH1_CHILD_ID);
  Serial.print(F(" V="));
  Serial.print(adc);
  Serial.print(F(" T="));
  Serial.println(temperature);
#endif
  send(msgTemp.set(temperature, 1));
}```

[ahmedadelhosni]

@tbowmo wow 2.5 years !! Which bootloader are you using for your sleeping node ? It is Sensebender or did you modify it ?

[tbowmo]

@ahmedadelhosni

It's the standard dualoptiboot, that we ship with the sensebender micro. But the bootloader is not essential in this context. What is essential, is how often you power up your radio etc. for transmitting.

My sketch for the sensors is more or less like the standard Sensebender Micro sketch that we have on github, which wakes up the mcu once every minute, takes a measurement and compare to the value last sent to the gateway. If the deviation is greater than X then transmit the new value. Otherwise, just go to sleep for 1 more minute.

Every half hour or so, I do a forced transmit of the measurement values. This to make sure it will report back periodically, so the controller get's some data for graphing.

[ahmedadelhosni]

@tbowmo Thanks for the info.

So here I have two questions. How do you power your node/radio ? how much days did it survive till now ?

[gohan]

@ahmedadelhosni If the node is using 10uA or less when sleeping, you should be expecting a battery life in the year range

[tbowmo]

@ahmedadelhosni

I'm powering my sensebenders (5 pcs) with 2xAA batteries, and they have been running for 2.5 years now, without changing batteries.

I think that this is a pretty decent battery life for a sensor :)

[ahmedadelhosni]

Thanks all.

Actually @tbowmo i was asking about bootloader because I have opened another thread reagrding a problem where my node stops working sometimes when i use 1 Mhz. So i was asking what would it be the problem ? And what booloader + power supply technique do people use.

[ahmedadelhosni]

@tbowmo are they alkaline or lithuim ?

[mfalkvidd]

I use alkaline. Easy to buy and cheap.

[tbowmo]

@ahmedadelhosni

Alkaline, cheap "IKEA" batteries.. :)

My units reports around 60% battery capacity left (very unscientifically measurements)

About operating frequency. If you have a sleeping node, then you won't gain anything from using 1Mhz versus 8Mhz, on the contrary you might end up using more power, when using 1Mhz, than 8Mhz. Because the time that the MCU is awake is longer at 1Mhz, than at 8Mhz. Remember, that when the MCU is sleeping, the power usage is the same, regardless of what frequency the MCU is working at, because the oscillator is shut down.

at 8Mhz you would complete your operation quicker, and return to sleep mode again faster, than when running at 1Mhz.