Battery operated Lux Sensor

  • Would like to show my first prototype of a battery operated Lux sensor. I have choosen to use a step up convertor to have a stable Vcc of 3.3V for the Pro Mini and the RFM69 radio. Using the battery power direct has drawbacks, the logic levels are fluctuating, the BOD detection of the Pro Mini is set to 2.7 V so I can not go to the minimum of 1V per cell. Using the step-up also has a drawback, it consumes a bit of power for itself. But it makes it possible to go down to the 1V per cell.

    Doing the measurements and calculations it should work for about 17 months (still theoretical !) on two AA alkaline batteries. The sensor sends in a lux value every 5 minutes, only when the value has changed. It also send the battery level, 0% is 2.0V, 100% is 3.0V. The prototype also sends the actual battery voltage but this is only for testing. This setup is running for a week now.

    It's still "under construction".

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    // Change baudrate to 9600 in c:\Users\Roland\Documents\Arduino\libraries\MySensors\MyConfig.h
    #include <MySigningNone.h>
    #include <MyTransportRFM69.h>
    #include <MyHwATMega328.h>
    #include <MySigningAtsha204Soft.h>
    #include <MySigningAtsha204.h>
    #include <MySensor.h>
    #include <SPI.h>
    #include <Wire.h> 
    #include <SFE_TSL2561.h>
    #define MY_DEBUG
    #define Led 3
    #define MeasurePoint1 4
    #define MeasurePoint2 5
    int BATTERY_SENSE_PIN = A0;  // select the input pin for the battery sense point
    // Create an SFE_TSL2561 object, here called "light":
    SFE_TSL2561 light;
    boolean gain;        // Gain setting, 0 = X1, 1 = X16;
    unsigned int ms;     // Integration ("shutter") time in milliseconds
    float Vref = 3.324;  // Vref in mV
    int VMIN = 2000;     //  Battery monitor low level in mV
    int VMAX = 3000;     //  Battery monitor high level in mV 
    int batteryPcnt;
    int LastbatteryPcnt = 0;
    int batterymV;
    float batteryV;
    int MeasureCount = 50; 
    // Define the child ID's 
    #define CHILD_ID_LIGHT 0
    #define CHILD_ID_VOLTMETER 1
    #define CHILD_ID_STATUS 2
    #ifdef MY_DEBUG
    unsigned long SLEEP_TIME = 60000; // Sleep time between reads (in milliseconds) 1 minute for testing
    unsigned long SLEEP_TIME = 300000; // Sleep time between reads (in milliseconds) 5 minutes
    MyTransportRFM69 transport;
    // Hardware profile
    MyHwATMega328 hw;
    // Construct MySensors library (signer needed if MY_SIGNING_FEATURE is turned on in MyConfig.h)
    // To use LEDs blinking, uncomment WITH_LEDS_BLINKING in MyConfig.h
    MySensor gw(transport, hw /*, signer*/, RADIO_RX_LED_PIN, RADIO_TX_LED_PIN, RADIO_ERROR_LED_PIN);
    MySensor gw(transport, hw /*, signer*/);
    // V_LIGHT_LEVEL should only be used for uncalibrated light level 0-100%.
    // If your controller supports the new V_LEVEL variable, use this instead for
    // transmitting LUX light level.
    // MyMessage luxmsg(CHILD_ID_LIGHT, V_LIGHT_LEVEL);
     MyMessage luxmsg(CHILD_ID_LIGHT, V_LEVEL);  
     MyMessage voltmsg(CHILD_ID_VOLTMETER, V_VOLTAGE);
     MyMessage statusmsg(CHILD_ID_STATUS, V_STATUS);
    uint16_t lastlux;
    uint16_t mlux;
    double lux;    // Resulting lux value
    boolean good;  // True if neither sensor is saturated
    void setup()  
      #ifdef MY_DEBUG
      pinMode(MeasurePoint1, OUTPUT);
      pinMode(MeasurePoint2, OUTPUT);
      pinMode(Led, OUTPUT);
      // Send the sketch version information to the gateway and Controller
      gw.sendSketchInfo("BattLuxSensor", "1.4");
      // Register all sensors to gateway (they will be created as child devices)
      gw.present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);
      gw.present(CHILD_ID_STATUS, S_BINARY);
      // Initialize the SFE_TSL2561 library
      // You can pass nothing to light.begin() for the default I2C address (0x39),
      // or use one of the following presets if you have changed
      // the ADDR jumper on the board:
      // TSL2561_ADDR_0 address with '0' shorted on board (0x29)
      // TSL2561_ADDR   default address (0x39)
      // TSL2561_ADDR_1 address with '1' shorted on board (0x49)
      // Get factory ID from sensor:
      // (Just for debug, you don't need to do this to operate the sensor)
      unsigned char ID;
    #ifdef MY_DEBUG
      if (light.getID(ID))
        Serial.print("Found TSL2561 light sensor at ID: 0X");
      // Most library commands will return true if communications was successful,
      // and false if there was a problem. You can ignore this returned value,
      // or check whether a command worked correctly and retrieve an error code:
        byte error = light.getError();
        Serial.println("TSL2561 light sensor not found");
      // The light sensor has a default integration time of 402ms,
      // and a default gain of low (1X).
      // If you would like to change either of these, you can
      // do so using the setTiming() command.
      // If gain = false (0), device is set to low gain (1X)
      // If gain = high (1), device is set to high gain (16X)
      gain = 0;
      // If time = 0, integration will be 13.7ms
      // If time = 1, integration will be 101ms
      // If time = 2, integration will be 402ms
      // If time = 3, use manual start / stop to perform your own integration
      unsigned char time = 1;
      // setTiming() will set the third parameter (ms) to the
      // requested integration time in ms (this will be useful later):
      #ifdef MY_DEBUG
      Serial.println("Set timing and gain TSL2561");
    void loop()      
      #ifdef MY_DEBUG
      // To start taking measurements, power up the sensor:
      #ifdef MY_DEBUG
      Serial.println("Powerup TSL2561");
      //light.manualStart();     // Do manual start
      delay(410);                // Wait integration time
      //light.manualStop();      // Do manual stop
      // Once integration is complete, we'll retrieve the data.
      // There are two light sensors on the device, one for visible light
      // and one for infrared. Both sensors are needed for lux calculations.
      // Retrieve the data from the device:
      unsigned int data0, data1;
      if (light.getData(data0,data1))
        // getData() returned true, communication was successful
        // To calculate lux, pass all your settings and readings
        // to the getLux() function.
        // The getLux() function will return 1 if the calculation
        // was successful, or 0 if one or both of the sensors was
        // saturated (too much light). If this happens, you can
        // reduce the integration time and/or gain.
        // For more information see the hookup guide at:
        // Perform lux calculation:
        good = light.getLux(gain,ms,data0,data1,lux);
        // getData() returned false because of an I2C error, inform the user.
        byte error = light.getError();
        #ifdef MY_DEBUG
      #ifdef MY_DEBUG
      Serial.print("LUX Measurement return flag : ");
        if (good) 
      // Convert lux to an integer
      mlux = int(lux); // Set Lux value to integer
      #ifdef MY_DEBUG
      Serial.print("Measured LUX value: ");
      Serial.println("Powerdown TSL2561");
      light.setPowerDown();    // Power down the sensor       
      // Get the battery Voltage
      // Do 50 measurements and average the result
      long Average = 0;      
        for(int i = 0; i < MeasureCount; i++) {
          Average = Average + analogRead(BATTERY_SENSE_PIN);
      int sensorValue = Average / MeasureCount;
      batteryV = sensorValue * (Vref / 1024.0);
      batterymV = int (1000 * batteryV);
      if (batterymV > 3000) batterymV = 3000;
      if (batterymV < 2000) batterymV = 2000;
      batteryPcnt = map(batterymV, VMIN, VMAX, 0, 100);  
      #ifdef MY_DEBUG
      Serial.print("ADC value: ");
      Serial.print("Battery Voltage: ");
      Serial.println(" V");
      Serial.print("Battery percent: ");
      Serial.println(" %");
      if ((batteryPcnt != LastbatteryPcnt) || (mlux != lastlux)) { 
        #ifdef MY_DEBUG
        // Send in status (good or bad)
        // Send in the Lux value
        // Send in the battery level percentage
        // Send in the battery voltage
        gw.send(voltmsg.set(batteryV, 2)); // Set wants volts and how many decimals (2 in our case)
        LastbatteryPcnt = batteryPcnt;
        lastlux = mlux;
      #ifdef MY_DEBUG
      #ifdef MY_DEBUG
    // ===========================================================
    #ifdef MY_DEBUG
    void printError(byte error)
      // If there's an I2C error, this function will
      // print out an explanation.
      Serial.print("I2C error: ");
      Serial.print(", ");
        case 0:
        case 1:
          Serial.println("data too long for transmit buffer");
        case 2:
          Serial.println("received NACK on address (disconnected?)");
        case 3:
          Serial.println("received NACK on data");
        case 4:
          Serial.println("other error");
          Serial.println("unknown error");

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