Lazy door bell sensor hack. this is only sensing when the door bell is actually ringing. This can't make the doorbell ring.

Find a cheap door bell, my hack is using this: 1 by One Wireless Door Chime R/X QH-0031 (Quhwa QH-09D) I bought this one in DK: http://www.jemogfix.dk/doerklokker__6754/traadloes-doerklokke_9025303

They are all made by Quhwa a Chinese company, mechanically they are the same, but sold in Europe during many different names, decided by the import company selling.

You don't need the interposer PCB that I have created and use, it's just convenient for me to re-use, to get NRF24L01+ and Arduino Pro Mini connected together https://www.openhardware.io/view/56/Mys-Interposer-NRFArduino-Pro-Mini

I am measuring the battery voltage, description here: https://www.mysensors.org/build/battery

To ensure that Arduino is not using all battery do the following:

1. Remove voltage DC converter
2. Remove power on LED

And also I have set BOD off, so Arduino will continue to work below 2,7V. To complete this I use a USBtinyISP to progam this.

avrdude -c usbtiny -p m328p -U efuse:w:0x07:m

I am still using mysesensor ver1.5.4, which my Arduino code is reflecting

//#include <Arduino.h>
#include <SPI.h>  
#include <MySensor.h>

#define CHILD_1  3  // childId
MySensor gw;
MyMessage msg(CHILD_1, V_TRIPPED);

#define PRIMARY_BUTTON_PIN 2   // Arduino Digital I/O pin for button/reed switch

//Define battery max, Min voltage levels
#define MIN_V 1900
#define MAX_V 3200
int BATTERY_SENSE_PIN = A0;  // select the input pin for the battery sense point

void setup()
{
  // use the 1.1 V internal reference
  #if defined(__AVR_ATmega2560__)
   analogReference(INTERNAL1V1);
  #else
   analogReference(INTERNAL);
  #endif  
  
  // Setup the buttons
  pinMode(PRIMARY_BUTTON_PIN, INPUT);
  
  
  Serial.begin(115200);
  //Serial.begin(9600);
  //delay(500);

 // Serial.println(F("Starting"));
  gw.begin();
   
  // Send the sketch version information to the gateway and Controller
  gw.sendSketchInfo("Door Bell Sensor", "1.0");

  // Register a sensors to gw. Use binary light for test purposes.
  //gw.present(CHILD_1, S_DOOR);
  gw.present(CHILD_1, S_MOTION);
 
 
}

void loop()
{
  uint8_t value;
  
  //value = digitalRead(PRIMARY_BUTTON_PIN);
    
  //gw.process();

  //if (value == 0) {
    gw.send(msg.set(1));
    Serial.println("ON");
    gw.sleep(3000);
    gw.send(msg.set(0));
    Serial.println("OFF");
    //gw.sleep(30000);
  //}
// get the battery Voltage
   int sensorValue = analogRead(BATTERY_SENSE_PIN);
   #ifdef DEBUG
   Serial.println(sensorValue);
   #endif
   // 1M, 470K divider across battery and using internal ADC ref of 1.1V
   // Sense point is bypassed with 0.1 uF cap to reduce noise at that point
   // ((1e6+470e3)/470e3)*1.1 = Vmax = 3.44 Volts
   // 3.44/1023 = Volts per bit = 0.003363075
   //   float batteryV  = sensorValue * 0.003363075;
   //   int batteryPcnt = sensorValue / 10;

   //bja   int batteryPcnt = min(map(readVcc(), MIN_V, MAX_V, 0, 100), 100); // Convert voltage to percentage
    
     int batteryPcnt = min(map(readVcc(), MIN_V, MAX_V, 0, 100), 100); // Convert voltage to percentage
        #ifdef DEBUG
         Serial.print("Battery Voltage: ");
         //Serial.print(batteryV);
         //Serial.println(" V");
         Serial.print("Battery percent: ");
         Serial.print(batteryPcnt);
         Serial.println(" %");
       #endif

     gw.sendBatteryLevel(batteryPcnt);

  gw.sleep(500);
  
  gw.sleep(PRIMARY_BUTTON_PIN-2, CHANGE, 0);
  
}
long readVcc() {
  // Read 1.1V reference against AVcc
  // set the reference to Vcc and the measurement to the internal 1.1V reference
  #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  
 
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA,ADSC)); // measuring
 
  uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH  
  uint8_t high = ADCH; // unlocks both
 
  long result = (high<<8) | low;
 
  result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
  return result; // Vcc in millivolts
}