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  3. Rebuild of my broken 433mhz Cresta/hideki UV-Sensor

Rebuild of my broken 433mhz Cresta/hideki UV-Sensor

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  • sundberg84S Offline
    sundberg84S Offline
    sundberg84
    Hardware Contributor
    wrote on last edited by
    #3

    Nice one! Good to have in the summe here when the kids are outside... I will build one as well.
    Thank you for sharing!

    Controller: Proxmox VM - Home Assistant
    MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
    MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
    RFLink GW - Arduino Mega + RFLink Shield, 433mhz

    1 Reply Last reply
    0
    • korttomaK Offline
      korttomaK Offline
      korttoma
      Hero Member
      wrote on last edited by
      #4

      I had plans to "MySensor" my Oregon scientific UV Index sensor when it fails ( It seems like it us quite common that they fail within 2 years ) but the darn thing just keeps working :sunglasses: been working for 5 years now...

      • Tomas
      1 Reply Last reply
      0
      • M Mediacj

        @edweather

        Great post thanks for sharing!

        I have also two of these which are not functioning anymore. Did you find a solution to the low values after all?

        E Offline
        E Offline
        edweather
        wrote on last edited by edweather
        #5

        Hello @Mediacj

        No I did not find a cause or sollution for the problem. After three broken sensors I gave up.
        I will give it a try next summer!

        Edwin

        1 Reply Last reply
        0
        • GizMoCuzG Offline
          GizMoCuzG Offline
          GizMoCuz
          wrote on last edited by
          #6

          I dont think it's a Sensor issue, rather a sketch issue....
          I bought 4 UV sensors, and also experiencing this.
          It could be that we need to multiply the value we send by 10 ? Or we need to do some magic after the analogRead call

          From what i understand the analogRead returns a value between 0-1023

          1023 stands for the maximum voltage that can be read on this pin, and equals VREF
          [Source](5 volts (on 5V Arduino boards) or 3.3 volts (on 3.3V Arduino boards))
          So if we use 3.3V on the arduino, then 1023 stands for 3.3V

          We go back from the digital value (0-1023) to voltage with:
          Source

          int sensorValue = analogRead(A0);
          float voltage= sensorValue * (3.3 / 1023.0);

          The above sketch is using mV, so we need to multiple the voltage by 1000

          float voltage= sensorValue * (3.3 / 1023.0) * 1000.0;

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          • sundberg84S Offline
            sundberg84S Offline
            sundberg84
            Hardware Contributor
            wrote on last edited by sundberg84
            #7

            How is the UV sensor / electronic best protected from rain and weather?
            Some sort of plastic lid? Or this will remove UV rays?

            I guess you want to point the sensor straight up where the rain comes from :)

            Controller: Proxmox VM - Home Assistant
            MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
            MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
            RFLink GW - Arduino Mega + RFLink Shield, 433mhz

            1 Reply Last reply
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            • GizMoCuzG Offline
              GizMoCuzG Offline
              GizMoCuz
              wrote on last edited by
              #8

              I use a plastic case like:
              http://www.aliexpress.com/item/Free-Shipping-115-90-55MM-Waterproof-Clear-Cover-Plastic-Electronic-Project-Box-Enclosure-Case/2025251375.html

              I now use the following code to read the uv value:

              #define         READ_SAMPLE_INTERVAL         (50)    //define how many samples you are going to take in normal operation
              #define         READ_SAMPLE_TIMES            (5)     //define the time interal(in milisecond) between each samples in  
              #define         VREF 5.0f
              
              float last_UVIndex = 0;
              uint16_t uvIndexValue [12] = { 50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; 
              
              float UVRead()
              {
                int i;
                float rs=0;
               
                for (i=0;i<READ_SAMPLE_TIMES;i++) {
                  rs += analogRead(UV_PIN);
                  delay(READ_SAMPLE_INTERVAL);
                }
               
                rs = rs/READ_SAMPLE_TIMES;
               
                return rs;  
              }
              
              float GetUVIndexFromVoltage(float voltage)
              {
                float UV=0;
                int i;
                for (i = 0; i < 12; i++)
                {
                  if (voltage <= uvIndexValue[i]) 
                  {
                    UV = float(i);
                    break;
                  }
                }
                
                //calculate 1 decimal if possible
                if (i>0) {
                  float vRange=float(uvIndexValue[i]-uvIndexValue[i-1]);
                  float vCalc=voltage-uvIndexValue[i-1];
                  UV+=(1.0f/vRange)*vCalc-1.0f;
                }
                return UV; 
              }
              
              void sendUVIRMeasurements(bool force)
              {
                bool tx=force;
              
                float sensorValue = UVRead();
                float voltage= sensorValue * (VREF / 1023.0f) * 1000.0f; //mV
                if (voltage>1170)
                  voltage=1170; 
                //Serial.print("UV Analog reading: ");
                //Serial.println(voltage,2);
                float UVIndex=GetUVIndexFromVoltage(voltage);
              
                float diffUV = abs(last_UVIndex - UVIndex);
              #ifdef MY_DEBUG
                Serial.print(F("diffUV :"));Serial.println(diffUV);
              #endif
                if (diffUV > 0.1) tx = true;
              
                if (!tx)
                  return;
              
                Serial.print("UVI: ");
                Serial.println(UVIndex,2);
              
                last_UVIndex = UVIndex;
              
                Serial.print("UV: ");
                Serial.println(UVIndex, 2);
                
              //  send(msgUV.set(UVIndex,2));
                //Avarage
                raUV.addValue(UVIndex);
                send(msgUV.set(raUV.getAverage(),2));
              }
              
              
              E 1 Reply Last reply
              0
              • GizMoCuzG GizMoCuz

                I use a plastic case like:
                http://www.aliexpress.com/item/Free-Shipping-115-90-55MM-Waterproof-Clear-Cover-Plastic-Electronic-Project-Box-Enclosure-Case/2025251375.html

                I now use the following code to read the uv value:

                #define         READ_SAMPLE_INTERVAL         (50)    //define how many samples you are going to take in normal operation
                #define         READ_SAMPLE_TIMES            (5)     //define the time interal(in milisecond) between each samples in  
                #define         VREF 5.0f
                
                float last_UVIndex = 0;
                uint16_t uvIndexValue [12] = { 50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; 
                
                float UVRead()
                {
                  int i;
                  float rs=0;
                 
                  for (i=0;i<READ_SAMPLE_TIMES;i++) {
                    rs += analogRead(UV_PIN);
                    delay(READ_SAMPLE_INTERVAL);
                  }
                 
                  rs = rs/READ_SAMPLE_TIMES;
                 
                  return rs;  
                }
                
                float GetUVIndexFromVoltage(float voltage)
                {
                  float UV=0;
                  int i;
                  for (i = 0; i < 12; i++)
                  {
                    if (voltage <= uvIndexValue[i]) 
                    {
                      UV = float(i);
                      break;
                    }
                  }
                  
                  //calculate 1 decimal if possible
                  if (i>0) {
                    float vRange=float(uvIndexValue[i]-uvIndexValue[i-1]);
                    float vCalc=voltage-uvIndexValue[i-1];
                    UV+=(1.0f/vRange)*vCalc-1.0f;
                  }
                  return UV; 
                }
                
                void sendUVIRMeasurements(bool force)
                {
                  bool tx=force;
                
                  float sensorValue = UVRead();
                  float voltage= sensorValue * (VREF / 1023.0f) * 1000.0f; //mV
                  if (voltage>1170)
                    voltage=1170; 
                  //Serial.print("UV Analog reading: ");
                  //Serial.println(voltage,2);
                  float UVIndex=GetUVIndexFromVoltage(voltage);
                
                  float diffUV = abs(last_UVIndex - UVIndex);
                #ifdef MY_DEBUG
                  Serial.print(F("diffUV :"));Serial.println(diffUV);
                #endif
                  if (diffUV > 0.1) tx = true;
                
                  if (!tx)
                    return;
                
                  Serial.print("UVI: ");
                  Serial.println(UVIndex,2);
                
                  last_UVIndex = UVIndex;
                
                  Serial.print("UV: ");
                  Serial.println(UVIndex, 2);
                  
                //  send(msgUV.set(UVIndex,2));
                  //Avarage
                  raUV.addValue(UVIndex);
                  send(msgUV.set(raUV.getAverage(),2));
                }
                
                
                E Offline
                E Offline
                edweather
                wrote on last edited by
                #9

                @GizMoCuz Nice to see that my old post suddenly comes to live! Thanks for sharing your sketch. It was one of my first builds so it could be the sketch but I also had strange readings using the sample code.
                Be cautious with the box you're using. Screws get rusty quick and water leakage will occur!
                I have ordered a GYML8511-Uv-sensor-module to try but I will try the old sensor first with your script!

                E 1 Reply Last reply
                0
                • sundberg84S Offline
                  sundberg84S Offline
                  sundberg84
                  Hardware Contributor
                  wrote on last edited by
                  #10

                  @GizMoCuz - Thanks for your box link. I have ordered one!
                  @edweather - Ill post some pictures when im done to keep it alive here!

                  Controller: Proxmox VM - Home Assistant
                  MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
                  MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
                  RFLink GW - Arduino Mega + RFLink Shield, 433mhz

                  1 Reply Last reply
                  0
                  • sundberg84S Offline
                    sundberg84S Offline
                    sundberg84
                    Hardware Contributor
                    wrote on last edited by sundberg84
                    #11

                    My UV sensors is complete!
                    (I have not recieved any case yet - so using a electronic box and a plastic bag :+1: )

                    0_1467280181315_1.jpg

                    Its a dual UV and light sensor (LM393 Light Sensor), running om my EasyPCB and 2xAA batteries.

                    First I had some problems with power consumption about 1500uA. This was caused by the light sensor and i removed all leds and what I could with the digital part. My sollution was to power the light sensor from D3 and put it high and then low before sleep. Now im down to 60uA. Also had some interferance with my booster and that worked out great by adding a 0.1cap between out and gnd.

                    Having some issues with measuring batteries and analogread. There is a correct reading on the input on the atmega328 pin (about 0.9v) but still get -80% when using analogread. Must be a faulty atmega chip.

                    My code: (Combined of @GizMoCuz and MySensors)

                    Code removed - please use code below
                    

                    Controller: Proxmox VM - Home Assistant
                    MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
                    MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
                    RFLink GW - Arduino Mega + RFLink Shield, 433mhz

                    core_cC 1 Reply Last reply
                    1
                    • E edweather

                      @GizMoCuz Nice to see that my old post suddenly comes to live! Thanks for sharing your sketch. It was one of my first builds so it could be the sketch but I also had strange readings using the sample code.
                      Be cautious with the box you're using. Screws get rusty quick and water leakage will occur!
                      I have ordered a GYML8511-Uv-sensor-module to try but I will try the old sensor first with your script!

                      E Offline
                      E Offline
                      edweather
                      wrote on last edited by
                      #12

                      Trying to get the GYML8511 sensor working with the example code from sparkfun.
                      Must be me again but the thing gives me strange outputs.

                      utput: 1023ML8511 output: 455 / ML8511 voltage: 1.47 / UV Intensity (mW/cm^2): 3.96
                      output: 1023ML8511 output: 688 / ML8511 voltage: 2.22 / UV Intensity (mW/cm^2): 10.19
                      output: 1023ML8511 output: 1023 / ML8511 voltage: 3.30 / UV Intensity (mW/cm^2): 19.14
                      output: 1023ML8511 output: 546 / ML8511 voltage: 1.76 / UV Intensity (mW/cm^2): 6.39
                      output: 1023ML8511 output: 568 / ML8511 voltage: 1.83 / UV Intensity (mW/cm^2): 6.98
                      output: 1023ML8511 output: 969 / ML8511 voltage: 3.13 / UV Intensity (mW/cm^2): 17.70
                      output: 1023ML8511 output: 842 / ML8511 voltage: 2.72 / UV Intensity (mW/cm^2): 14.30
                      output: 1023ML8511 output: 488 / ML8511 voltage: 1.57 / UV Intensity (mW/cm^2): 4.84
                      output: 1023ML8511 output: 748 / ML8511 voltage: 2.41 / UV Intensity (mW/cm^2): 11.79
                      output: 1023ML8511 output: 1017 / ML8511 voltage: 3.28 / UV Intensity (mW/cm^2): 18.98
                      output: 1023ML8511 output: 500 / ML8511 voltage: 1.61 / UV Intensity (mW/cm^2): 5.16
                      output: 1023ML8511 output: 629 / ML8511 voltage: 2.03 / UV Intensity (mW/cm^2): 8.61
                      output: 1023ML8511 output: 1017 / ML8511 voltage: 3.28 / UV Intensity (mW/cm^2): 18.98
                      output: 1023ML8511 output: 645 / ML8511 voltage: 2.08 / UV Intensity (mW/cm^2): 9.04
                      output: 1023ML8511 output: 502 / ML8511 voltage: 1.62 / UV Intensity (mW/cm^2): 5.22
                      output: 1023ML8511 output: 936 / ML8511 voltage: 3.02 / UV Intensity (mW/cm^2): 16.82
                      output: 1023ML8511 output: 950 / ML8511 voltage: 3.06 / UV Intensity (mW/cm^2): 17.19
                      output: 1023ML8511 output: 448 / ML8511 voltage: 1.45 / UV Intensity (mW/cm^2): 3.77
                      output: 1023ML8511 output: 711 / ML8511 voltage: 2.29 / UV Intensity (mW/cm^2): 10.80
                      output: 1023ML8511 output: 1023 / ML8511 voltage: 3.30 / UV Intensity (mW/cm^2): 19.14
                      output: 1023ML8511 output: 499 / ML8511 voltage: 1.61 / UV Intensity (mW/cm^2): 5.14
                      output: 1023ML8511 output: 607 / ML8511 voltage: 1.96 / UV Intensity (mW/cm^2): 8.02
                      output: 1023ML8511 output: 1014 / ML8511 voltage: 3.27 / UV Intensity (mW/cm^2): 18.90
                      output: 1023ML8511 output: 639 / ML8511 voltage: 2.06 / UV Intensity (mW/cm^2): 8.88
                      output: 1023ML8511 output: 541 / ML8511 voltage: 1.75 / UV Intensity (mW/cm^2): 6.26
                      output: 1023ML8511 output: 888 / ML8511 voltage: 2.86 / UV Intensity (mW/cm^2): 15.53
                      output: 1023ML8511 output: 903 / ML8511 voltage: 2.91 / UV Intensity (mW/cm^2): 15.94
                      output: 1023ML8511 output: 516 / ML8511 voltage: 1.66 / UV Intensity (mW/cm^2): 5.59
                      output: 1023ML8511 output: 738 / ML8511 voltage: 2.38 / UV Intensity (mW/cm^2): 11.52
                      output: 1023ML8511 output: 1007 / ML8511 voltage: 3.25 / UV Intensity (mW/cm^2): 18.72
                      output: 1023ML8511 output: 531 / ML8511 voltage: 1.71 / UV Intensity (mW/cm^2): 5.99
                      output: 1023ML8511 output: 656 / ML8511 voltage: 2.12 / UV Intensity (mW/cm^2): 9.33
                      output: 1023ML8511 output: 1020 / ML8511 voltage: 3.29 / UV Intensity (mW/cm^2): 19.06
                      output: 1023ML8511 output: 635 / ML8511 voltage: 2.05 / UV Intensity (mW/cm^2): 8.77
                      output: 1023ML8511 output: 542 / ML8511 voltage: 1.75 / UV Intensity (mW/cm^2): 6.28
                      output: 1023ML8511 output: 878 / ML8511 voltage: 2.83 / UV Intensity (mW/cm^2): 15.27
                      output: 1023ML8511 output: 915 / ML8511 voltage: 2.95 / UV Intensity (mW/cm^2): 16.26
                      output: 1023ML8511 output: 529 / ML8511 voltage: 1.71 / UV Intensity (mW/cm^2): 5.94
                      output: 1023ML8511 output: 733 / ML8511 voltage: 2.36 / UV Intensity (mW/cm^2): 11.39
                      output: 1023ML8511 output: 1009 / ML8511 voltage: 3.25 / UV Intensity (mW/cm^2): 18.77
                      output: 1023ML8511 output: 534 / ML8511 voltage: 1.72 / UV Intensity (mW/cm^2): 6.07
                      output: 1023ML8511 output: 676 / ML8511 voltage: 2.18 / UV Intensity (mW/cm^2): 9.87
                      output: 1023ML8511 output: 1021 / ML8511 voltage: 3.29 / UV Intensity (mW/cm^2): 19.09

                      Checked wiring again and again, even replaced wires and nano pro.

                      On my way to Aliexpress to buy a uvm30a

                      resources used:
                      http://twenty5nov.blogspot.nl/2016/02/gym8511ml-uv-sensor-connection-to.html
                      https://learn.sparkfun.com/tutorials/ml8511-uv-sensor-hookup-guide

                      0_1469283551311_20160723_141457345_iOS.jpg image url)

                      1 Reply Last reply
                      0
                      • sundberg84S sundberg84

                        My UV sensors is complete!
                        (I have not recieved any case yet - so using a electronic box and a plastic bag :+1: )

                        0_1467280181315_1.jpg

                        Its a dual UV and light sensor (LM393 Light Sensor), running om my EasyPCB and 2xAA batteries.

                        First I had some problems with power consumption about 1500uA. This was caused by the light sensor and i removed all leds and what I could with the digital part. My sollution was to power the light sensor from D3 and put it high and then low before sleep. Now im down to 60uA. Also had some interferance with my booster and that worked out great by adding a 0.1cap between out and gnd.

                        Having some issues with measuring batteries and analogread. There is a correct reading on the input on the atmega328 pin (about 0.9v) but still get -80% when using analogread. Must be a faulty atmega chip.

                        My code: (Combined of @GizMoCuz and MySensors)

                        Code removed - please use code below
                        
                        core_cC Offline
                        core_cC Offline
                        core_c
                        wrote on last edited by
                        #13

                        @sundberg84 You mention that you have an ATmega328.
                        In your sketch setup() function you set the reference voltage value:
                        analogReference(INTERNAL);
                        According to the Arduino Language Reference pages, [https://www.arduino.cc/en/Reference/AnalogReference](link url)
                        , on an ATmega328 that will set the analog reference value to 1.1V.
                        Any 10-bit sample taken by that ATmega328 will spread 1.1V out over 1024 values. In your code, you do the calculation using 3.3V as the AREF. That will produce 3 times smaller samplevalues as intended.

                        I see quite some people using code derived from the UV-example-sketch.
                        The code is a bit tricky, and in my opinion: not correct.

                        *) In your own code, you convert samplevalues to mV values: Very good. That should be done. The example does not do that.

                        *) The piece of code that returns the UV-index does this:

                        for (i=0; i<12; i++)
                          if (voltage <= uvIndexValue[i]) {
                            UV=float(i); break;
                          }
                        

                        It returns a value that is 1 index too high. (try it: 317 mV will return UV=2).
                        But later a fractional part of the UV-index is calculated, which corrects the initial (too high) value:

                        //calculate 1 decimal if possible
                        if (i > 0) {
                          float vRange = float(uvIndexValue[i] - uvIndexValue[i - 1]);
                          float vCalc = voltage - uvIndexValue[i - 1];
                          UV += (1.0f / vRange) * vCalc - 1.0f;
                        }
                        

                        At first glance it looks like the value UV will even get bigger (UV+=something), but it turns out that always a negative number is added to UV.
                        (1.0f / vRange) * vCalc - 1.0f is always negative. So something is subtracted from the initial value UV.
                        It's a bit counter intuitive...

                        I've seen other people's projects where they removed the fractional/decimal part from their code (unlike your code). Their sensors will therefore always be interpreted with a full 1 UV-index value too high.

                        *) Correct me if i'm wrong, but the example code calculates a UV-index with a one-decimal precision. But the value sent to the gateway, is sent in 2 decimals. Wouldn't it be enough to do:

                        send(msgUV.set(UVindex, 1));
                        

                        Here are bits of my own code. I use the Arduino map() function to calculate the decimal for me.
                        Perhaps others find it easier to read too.:

                        const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // in units of mV
                        const float SAMPLE_TO_MV = (1.1*1000)/1024;  // mV per sample-resolution
                        
                        uint16_t UV_index;        // the UV index
                        uint16_t UV_index_f;      // the fractional part of the UV index
                        
                        ...
                        
                        // determine the UV index
                        if (UV_value < UV_threshold[0]) {
                          // too low value  or 
                          // invalid value (sensor is wrongly connected? => always 0)
                          UV_index = 0;
                          UV_index_f = 0;
                        } else {
                          for (UV_index=11; UV_index>0; UV_index--)
                            if (UV_value >= UV_threshold[UV_index]) break;
                          // calculate fractional part of the UV-index
                          if (UV_index == 11) {
                            // already at the maximum level;
                            // Displaying a fraction is meaningless
                            UV_index_f = 0;
                          } else {
                            UV_index_f = map(UV_value, UV_threshold[UV_index],UV_threshold[UV_index+1], 0,9);
                            // one decimal, so a number ranging 0 to 9
                          }
                        }
                        float UV_index_float = UV_index + (UV_index_f/10.0);
                        
                        sundberg84S M 2 Replies Last reply
                        1
                        • core_cC core_c

                          @sundberg84 You mention that you have an ATmega328.
                          In your sketch setup() function you set the reference voltage value:
                          analogReference(INTERNAL);
                          According to the Arduino Language Reference pages, [https://www.arduino.cc/en/Reference/AnalogReference](link url)
                          , on an ATmega328 that will set the analog reference value to 1.1V.
                          Any 10-bit sample taken by that ATmega328 will spread 1.1V out over 1024 values. In your code, you do the calculation using 3.3V as the AREF. That will produce 3 times smaller samplevalues as intended.

                          I see quite some people using code derived from the UV-example-sketch.
                          The code is a bit tricky, and in my opinion: not correct.

                          *) In your own code, you convert samplevalues to mV values: Very good. That should be done. The example does not do that.

                          *) The piece of code that returns the UV-index does this:

                          for (i=0; i<12; i++)
                            if (voltage <= uvIndexValue[i]) {
                              UV=float(i); break;
                            }
                          

                          It returns a value that is 1 index too high. (try it: 317 mV will return UV=2).
                          But later a fractional part of the UV-index is calculated, which corrects the initial (too high) value:

                          //calculate 1 decimal if possible
                          if (i > 0) {
                            float vRange = float(uvIndexValue[i] - uvIndexValue[i - 1]);
                            float vCalc = voltage - uvIndexValue[i - 1];
                            UV += (1.0f / vRange) * vCalc - 1.0f;
                          }
                          

                          At first glance it looks like the value UV will even get bigger (UV+=something), but it turns out that always a negative number is added to UV.
                          (1.0f / vRange) * vCalc - 1.0f is always negative. So something is subtracted from the initial value UV.
                          It's a bit counter intuitive...

                          I've seen other people's projects where they removed the fractional/decimal part from their code (unlike your code). Their sensors will therefore always be interpreted with a full 1 UV-index value too high.

                          *) Correct me if i'm wrong, but the example code calculates a UV-index with a one-decimal precision. But the value sent to the gateway, is sent in 2 decimals. Wouldn't it be enough to do:

                          send(msgUV.set(UVindex, 1));
                          

                          Here are bits of my own code. I use the Arduino map() function to calculate the decimal for me.
                          Perhaps others find it easier to read too.:

                          const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // in units of mV
                          const float SAMPLE_TO_MV = (1.1*1000)/1024;  // mV per sample-resolution
                          
                          uint16_t UV_index;        // the UV index
                          uint16_t UV_index_f;      // the fractional part of the UV index
                          
                          ...
                          
                          // determine the UV index
                          if (UV_value < UV_threshold[0]) {
                            // too low value  or 
                            // invalid value (sensor is wrongly connected? => always 0)
                            UV_index = 0;
                            UV_index_f = 0;
                          } else {
                            for (UV_index=11; UV_index>0; UV_index--)
                              if (UV_value >= UV_threshold[UV_index]) break;
                            // calculate fractional part of the UV-index
                            if (UV_index == 11) {
                              // already at the maximum level;
                              // Displaying a fraction is meaningless
                              UV_index_f = 0;
                            } else {
                              UV_index_f = map(UV_value, UV_threshold[UV_index],UV_threshold[UV_index+1], 0,9);
                              // one decimal, so a number ranging 0 to 9
                            }
                          }
                          float UV_index_float = UV_index + (UV_index_f/10.0);
                          
                          sundberg84S Offline
                          sundberg84S Offline
                          sundberg84
                          Hardware Contributor
                          wrote on last edited by
                          #14

                          @core_c - looks good! Thank you. Coding isnt my strong side so appreciated you looked at it!

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                          • core_cC core_c

                            @sundberg84 You mention that you have an ATmega328.
                            In your sketch setup() function you set the reference voltage value:
                            analogReference(INTERNAL);
                            According to the Arduino Language Reference pages, [https://www.arduino.cc/en/Reference/AnalogReference](link url)
                            , on an ATmega328 that will set the analog reference value to 1.1V.
                            Any 10-bit sample taken by that ATmega328 will spread 1.1V out over 1024 values. In your code, you do the calculation using 3.3V as the AREF. That will produce 3 times smaller samplevalues as intended.

                            I see quite some people using code derived from the UV-example-sketch.
                            The code is a bit tricky, and in my opinion: not correct.

                            *) In your own code, you convert samplevalues to mV values: Very good. That should be done. The example does not do that.

                            *) The piece of code that returns the UV-index does this:

                            for (i=0; i<12; i++)
                              if (voltage <= uvIndexValue[i]) {
                                UV=float(i); break;
                              }
                            

                            It returns a value that is 1 index too high. (try it: 317 mV will return UV=2).
                            But later a fractional part of the UV-index is calculated, which corrects the initial (too high) value:

                            //calculate 1 decimal if possible
                            if (i > 0) {
                              float vRange = float(uvIndexValue[i] - uvIndexValue[i - 1]);
                              float vCalc = voltage - uvIndexValue[i - 1];
                              UV += (1.0f / vRange) * vCalc - 1.0f;
                            }
                            

                            At first glance it looks like the value UV will even get bigger (UV+=something), but it turns out that always a negative number is added to UV.
                            (1.0f / vRange) * vCalc - 1.0f is always negative. So something is subtracted from the initial value UV.
                            It's a bit counter intuitive...

                            I've seen other people's projects where they removed the fractional/decimal part from their code (unlike your code). Their sensors will therefore always be interpreted with a full 1 UV-index value too high.

                            *) Correct me if i'm wrong, but the example code calculates a UV-index with a one-decimal precision. But the value sent to the gateway, is sent in 2 decimals. Wouldn't it be enough to do:

                            send(msgUV.set(UVindex, 1));
                            

                            Here are bits of my own code. I use the Arduino map() function to calculate the decimal for me.
                            Perhaps others find it easier to read too.:

                            const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // in units of mV
                            const float SAMPLE_TO_MV = (1.1*1000)/1024;  // mV per sample-resolution
                            
                            uint16_t UV_index;        // the UV index
                            uint16_t UV_index_f;      // the fractional part of the UV index
                            
                            ...
                            
                            // determine the UV index
                            if (UV_value < UV_threshold[0]) {
                              // too low value  or 
                              // invalid value (sensor is wrongly connected? => always 0)
                              UV_index = 0;
                              UV_index_f = 0;
                            } else {
                              for (UV_index=11; UV_index>0; UV_index--)
                                if (UV_value >= UV_threshold[UV_index]) break;
                              // calculate fractional part of the UV-index
                              if (UV_index == 11) {
                                // already at the maximum level;
                                // Displaying a fraction is meaningless
                                UV_index_f = 0;
                              } else {
                                UV_index_f = map(UV_value, UV_threshold[UV_index],UV_threshold[UV_index+1], 0,9);
                                // one decimal, so a number ranging 0 to 9
                              }
                            }
                            float UV_index_float = UV_index + (UV_index_f/10.0);
                            
                            M Offline
                            M Offline
                            Mediacj
                            wrote on last edited by Mediacj
                            #15

                            @core_c
                            Thanks for sharing! It was my experience to that the sample values were to low.

                            Is it possible to share your complete version?

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                            • core_cC Offline
                              core_cC Offline
                              core_c
                              wrote on last edited by core_c
                              #16

                              I stripped the code to only include the UV measurement.
                              Hopefully it helps you out a bit.

                              
                              // Print debug information (test versions), (or not; in the final version)
                              #define DEBUG_PRINT     // print debug information when this line is uncommented (and the next line is commented)
                              //#undef DEBUG_PRINT    // (vice versa)
                              
                              
                              
                              //===================================================
                              // UVM30A ultraviolet detector.
                              // The sensor's VCC is connected to +5V
                              //
                              // At first glance, the datasheet is not entirely making sense:
                              //  "输出电压" translates to "Output voltage", with a value of: DC 0—1V.
                              //  So the sensor will never output/measure the 2 highest values listed in the graph & table of the datasheet (1079 and 1170+).
                              //  The datasheet explains it: "(对应 UV 指数 0-10)" translates to "(corresponding to UV index 0-10)".  Fair enough.
                              // 
                              //  "测试精度" translates to: "Test accuracy", with a value of: ±1 UV INDEX
                              //  That is not very accurate on a range 0-10. Example: if the real UV-index is 4, you could measure 3, or 5.
                              //  For that reason we take an average of multiple samples, to get a better measurement.
                              
                              // The sensor's (analog) output is connected to the Arduino Nano's at pin 14 (A0)
                              #define UV_PIN 14
                              
                              // The list of UV index thresholds (in mV).
                              const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // in units of mV
                              
                              // The read value is a 10-bit value, ranging from 0 to 2^10-1 (0 to 1023).
                              // The reference voltage on the input pin is set to 1.1V.
                              // That voltage is spread out over the 1024 possible values of a sample.
                              // So our achieved resolution equals (1.1 Volts / 1024) = 0.00107421875 Volt.
                              // The UVM30A sensor datasheet lists all UV-index values according to measured milli-Volts.
                              const float SAMPLE_TO_MV = (1.1*1000)/1024;  // mV per sample-resolution
                              
                              uint16_t UV_value; 
                              uint16_t UV_index;        // the UV index
                              uint16_t UV_index_f;      // the fractional part of the UV index
                              
                              // Compiler directives for averiging the UV-sensor readings
                              // (Change the values of UV_AVERAGE_T & UV_AVERAGE_N according to your own taste).
                              #define UV_AVERAGE_T 4000 // Sample interval duration in milliseconds..  (1 <= T <= 60000)
                              #define UV_AVERAGE_N 10   // ..During that interval, N samples are taken, and averaged.    (1 <= N <= 100, must be <>0)
                              
                              #if UV_AVERAGE_T < 1      // Sanity check. It must be dummy proof
                              #define UV_AVERAGE_T 1
                              #endif
                              #if UV_AVERAGE_N < 1      // Sanity check. It must be dummy proof
                              #define UV_AVERAGE_N 1    // This value must be <>0 at all times, because we divide by it
                              #endif
                              
                              // calculate once, use many times in the loop()
                              const float UV_AVERAGE_N_RP = 1.0 / UV_AVERAGE_N;
                              const uint32_t UV_AVERAGE_D = UV_AVERAGE_T * UV_AVERAGE_N_RP;
                              //===================================================
                              
                              
                              //===================================================
                              // Process a UV measurement:
                              // read an average value from the UV detector.
                              // The average consists of N samples taken during a T milliseconds interval.
                              //===================================================
                              void processUV() {
                                // Set the reference voltage for sampling
                                // For our ATmega328 Nano: INTERNAL = 1.1V, DEFAULT = 5V
                                // After using analogReference(), the first few samples may not be accurate (according to the Arduino language reference),
                                // and that is why we read a few dummy samples before starting the actual measurement.
                                // NOTE: If you change the next statement, beware to adjust the value of SAMPLE_TO_MV too.
                                analogReference(INTERNAL);
                                for (int i=0; i<10; i++) UV_value = analogRead(UV_PIN);  // ignore the possibly inaccurate samplevalues.
                              
                                #ifdef DEBUG_PRINT
                                  Serial.print("UV raw values: [");  
                                #endif
                                uint32_t average = 0;
                                for (int i=0; i<UV_AVERAGE_N; i++) {
                                  #ifdef DEBUG_PRINT
                                    UV_value = analogRead(UV_PIN);
                                    Serial.print(UV_value);  Serial.print(" ");
                                    average += UV_value;
                                  #else
                                    average += analogRead(UV_PIN);
                                  #endif
                                  delay(UV_AVERAGE_D);
                                }
                                UV_value = average * UV_AVERAGE_N_RP;
                                #ifdef DEBUG_PRINT
                                  Serial.print("]    avg: ");  Serial.print(UV_value);
                                #endif
                              
                                // We must convert sample-values into mV-values before we look up the UV-index.
                                UV_value *= SAMPLE_TO_MV;
                              
                                #ifdef DEBUG_PRINT
                                  Serial.print("     mV: ");  Serial.print(UV_value);
                                #endif
                              
                                // determine the UV index
                                if (UV_value < UV_threshold[0]) {
                                  // too low value  or  invalid value (in case the sensor is wrongly connected it always returns 0)
                                  UV_index = 0;
                                  UV_index_f = 0;
                                } else {
                                  for (UV_index=11; UV_index>0; UV_index--) {
                                    if (UV_value >= UV_threshold[UV_index]) break;
                                  }
                                  // calculate fractional part of the UV-index
                                  if (UV_index == 11) {
                                    // already at the maximum level; Displaying a fraction is meaningless
                                    UV_index_f = 0;
                                  } else {
                                    UV_index_f = map(UV_value, UV_threshold[UV_index],UV_threshold[UV_index+1], 0,9);  // one decimal, so a number ranging 0 to 9
                                  }
                                }
                                float UV_index_float = UV_index + (UV_index_f*0.1);  // that is the same as /10
                              
                                #ifdef DEBUG_PRINT
                                  Serial.print("     UV index: ");  Serial.println(UV_index_float);
                                #endif
                              }
                              
                              
                              void setup() {
                                // By default the Arduino sets all pins as input at startup,
                                // so there is no need to explicitly set the pinMode
                                pinMode(UV_PIN, INPUT);
                                
                                #ifdef DEBUG_PRINT
                                  // debug purposes
                                  Serial.begin(9600);
                                #endif
                              }
                              
                              
                              void loop() {
                                // UV measurement
                                processUV();
                              
                                // just some delay
                                for (int i=0; i<5; i++) delay(1000);
                              }
                              

                              I edited my post.
                              The reason is that i'm using an Arduino Uno & Arduino Yún in my own project.
                              The Nano's pin numbering is quite different: pin named A0 is numbered 14.
                              If You copy/paste the code, and run it, it would look something like this:

                              UV raw values: [351 353 339 343 349 349 334 346 338 347 ]    avg: 344     mV: 369     UV index: 2.50
                              UV raw values: [344 344 344 348 343 341 349 346 345 349 ]    avg: 345     mV: 370     UV index: 2.50
                              UV raw values: [348 345 309 343 342 346 315 346 343 346 ]    avg: 338     mV: 363     UV index: 2.40
                              UV raw values: [330 317 343 340 343 343 341 338 342 341 ]    avg: 337     mV: 362     UV index: 2.40
                              UV raw values: [338 337 312 337 335 335 336 299 342 338 ]    avg: 330     mV: 354     UV index: 2.30
                              
                              sundberg84S 1 Reply Last reply
                              1
                              • core_cC core_c

                                I stripped the code to only include the UV measurement.
                                Hopefully it helps you out a bit.

                                
                                // Print debug information (test versions), (or not; in the final version)
                                #define DEBUG_PRINT     // print debug information when this line is uncommented (and the next line is commented)
                                //#undef DEBUG_PRINT    // (vice versa)
                                
                                
                                
                                //===================================================
                                // UVM30A ultraviolet detector.
                                // The sensor's VCC is connected to +5V
                                //
                                // At first glance, the datasheet is not entirely making sense:
                                //  "输出电压" translates to "Output voltage", with a value of: DC 0—1V.
                                //  So the sensor will never output/measure the 2 highest values listed in the graph & table of the datasheet (1079 and 1170+).
                                //  The datasheet explains it: "(对应 UV 指数 0-10)" translates to "(corresponding to UV index 0-10)".  Fair enough.
                                // 
                                //  "测试精度" translates to: "Test accuracy", with a value of: ±1 UV INDEX
                                //  That is not very accurate on a range 0-10. Example: if the real UV-index is 4, you could measure 3, or 5.
                                //  For that reason we take an average of multiple samples, to get a better measurement.
                                
                                // The sensor's (analog) output is connected to the Arduino Nano's at pin 14 (A0)
                                #define UV_PIN 14
                                
                                // The list of UV index thresholds (in mV).
                                const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // in units of mV
                                
                                // The read value is a 10-bit value, ranging from 0 to 2^10-1 (0 to 1023).
                                // The reference voltage on the input pin is set to 1.1V.
                                // That voltage is spread out over the 1024 possible values of a sample.
                                // So our achieved resolution equals (1.1 Volts / 1024) = 0.00107421875 Volt.
                                // The UVM30A sensor datasheet lists all UV-index values according to measured milli-Volts.
                                const float SAMPLE_TO_MV = (1.1*1000)/1024;  // mV per sample-resolution
                                
                                uint16_t UV_value; 
                                uint16_t UV_index;        // the UV index
                                uint16_t UV_index_f;      // the fractional part of the UV index
                                
                                // Compiler directives for averiging the UV-sensor readings
                                // (Change the values of UV_AVERAGE_T & UV_AVERAGE_N according to your own taste).
                                #define UV_AVERAGE_T 4000 // Sample interval duration in milliseconds..  (1 <= T <= 60000)
                                #define UV_AVERAGE_N 10   // ..During that interval, N samples are taken, and averaged.    (1 <= N <= 100, must be <>0)
                                
                                #if UV_AVERAGE_T < 1      // Sanity check. It must be dummy proof
                                #define UV_AVERAGE_T 1
                                #endif
                                #if UV_AVERAGE_N < 1      // Sanity check. It must be dummy proof
                                #define UV_AVERAGE_N 1    // This value must be <>0 at all times, because we divide by it
                                #endif
                                
                                // calculate once, use many times in the loop()
                                const float UV_AVERAGE_N_RP = 1.0 / UV_AVERAGE_N;
                                const uint32_t UV_AVERAGE_D = UV_AVERAGE_T * UV_AVERAGE_N_RP;
                                //===================================================
                                
                                
                                //===================================================
                                // Process a UV measurement:
                                // read an average value from the UV detector.
                                // The average consists of N samples taken during a T milliseconds interval.
                                //===================================================
                                void processUV() {
                                  // Set the reference voltage for sampling
                                  // For our ATmega328 Nano: INTERNAL = 1.1V, DEFAULT = 5V
                                  // After using analogReference(), the first few samples may not be accurate (according to the Arduino language reference),
                                  // and that is why we read a few dummy samples before starting the actual measurement.
                                  // NOTE: If you change the next statement, beware to adjust the value of SAMPLE_TO_MV too.
                                  analogReference(INTERNAL);
                                  for (int i=0; i<10; i++) UV_value = analogRead(UV_PIN);  // ignore the possibly inaccurate samplevalues.
                                
                                  #ifdef DEBUG_PRINT
                                    Serial.print("UV raw values: [");  
                                  #endif
                                  uint32_t average = 0;
                                  for (int i=0; i<UV_AVERAGE_N; i++) {
                                    #ifdef DEBUG_PRINT
                                      UV_value = analogRead(UV_PIN);
                                      Serial.print(UV_value);  Serial.print(" ");
                                      average += UV_value;
                                    #else
                                      average += analogRead(UV_PIN);
                                    #endif
                                    delay(UV_AVERAGE_D);
                                  }
                                  UV_value = average * UV_AVERAGE_N_RP;
                                  #ifdef DEBUG_PRINT
                                    Serial.print("]    avg: ");  Serial.print(UV_value);
                                  #endif
                                
                                  // We must convert sample-values into mV-values before we look up the UV-index.
                                  UV_value *= SAMPLE_TO_MV;
                                
                                  #ifdef DEBUG_PRINT
                                    Serial.print("     mV: ");  Serial.print(UV_value);
                                  #endif
                                
                                  // determine the UV index
                                  if (UV_value < UV_threshold[0]) {
                                    // too low value  or  invalid value (in case the sensor is wrongly connected it always returns 0)
                                    UV_index = 0;
                                    UV_index_f = 0;
                                  } else {
                                    for (UV_index=11; UV_index>0; UV_index--) {
                                      if (UV_value >= UV_threshold[UV_index]) break;
                                    }
                                    // calculate fractional part of the UV-index
                                    if (UV_index == 11) {
                                      // already at the maximum level; Displaying a fraction is meaningless
                                      UV_index_f = 0;
                                    } else {
                                      UV_index_f = map(UV_value, UV_threshold[UV_index],UV_threshold[UV_index+1], 0,9);  // one decimal, so a number ranging 0 to 9
                                    }
                                  }
                                  float UV_index_float = UV_index + (UV_index_f*0.1);  // that is the same as /10
                                
                                  #ifdef DEBUG_PRINT
                                    Serial.print("     UV index: ");  Serial.println(UV_index_float);
                                  #endif
                                }
                                
                                
                                void setup() {
                                  // By default the Arduino sets all pins as input at startup,
                                  // so there is no need to explicitly set the pinMode
                                  pinMode(UV_PIN, INPUT);
                                  
                                  #ifdef DEBUG_PRINT
                                    // debug purposes
                                    Serial.begin(9600);
                                  #endif
                                }
                                
                                
                                void loop() {
                                  // UV measurement
                                  processUV();
                                
                                  // just some delay
                                  for (int i=0; i<5; i++) delay(1000);
                                }
                                

                                I edited my post.
                                The reason is that i'm using an Arduino Uno & Arduino Yún in my own project.
                                The Nano's pin numbering is quite different: pin named A0 is numbered 14.
                                If You copy/paste the code, and run it, it would look something like this:

                                UV raw values: [351 353 339 343 349 349 334 346 338 347 ]    avg: 344     mV: 369     UV index: 2.50
                                UV raw values: [344 344 344 348 343 341 349 346 345 349 ]    avg: 345     mV: 370     UV index: 2.50
                                UV raw values: [348 345 309 343 342 346 315 346 343 346 ]    avg: 338     mV: 363     UV index: 2.40
                                UV raw values: [330 317 343 340 343 343 341 338 342 341 ]    avg: 337     mV: 362     UV index: 2.40
                                UV raw values: [338 337 312 337 335 335 336 299 342 338 ]    avg: 330     mV: 354     UV index: 2.30
                                
                                sundberg84S Offline
                                sundberg84S Offline
                                sundberg84
                                Hardware Contributor
                                wrote on last edited by sundberg84
                                #17

                                @core_c - If I change the analogReference(INTERNAL); will this change all readings on all analog pins? Im using this becuse of a voltage divider that returns the battery status.

                                Because if thats true - I think we need to inform this at our battery build instruction. Using this is very common with battery powered sensors and if this is making error values for analog readings...

                                @awi? Any imput? I know you have a great battery knowledge.

                                Its getting into the season so I will update my Sensor and see if I can combine it with battery measurement as well. Thanks.

                                Edit: Or I might missunderstood this completley... If the sensors return 3.3v as maxoutput, Can i still combine this sensor with the battery report using analogref(internal) or should I read the batterystatus some other way? I see you use analogReference(INTERNAL) as well using this sensor. Did I just make the code the wrong way?

                                Controller: Proxmox VM - Home Assistant
                                MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
                                MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
                                RFLink GW - Arduino Mega + RFLink Shield, 433mhz

                                AWIA 1 Reply Last reply
                                1
                                • sundberg84S sundberg84

                                  @core_c - If I change the analogReference(INTERNAL); will this change all readings on all analog pins? Im using this becuse of a voltage divider that returns the battery status.

                                  Because if thats true - I think we need to inform this at our battery build instruction. Using this is very common with battery powered sensors and if this is making error values for analog readings...

                                  @awi? Any imput? I know you have a great battery knowledge.

                                  Its getting into the season so I will update my Sensor and see if I can combine it with battery measurement as well. Thanks.

                                  Edit: Or I might missunderstood this completley... If the sensors return 3.3v as maxoutput, Can i still combine this sensor with the battery report using analogref(internal) or should I read the batterystatus some other way? I see you use analogReference(INTERNAL) as well using this sensor. Did I just make the code the wrong way?

                                  AWIA Offline
                                  AWIA Offline
                                  AWI
                                  Hero Member
                                  wrote on last edited by AWI
                                  #18

                                  @sundberg84 The internal reference is around 1.1V. A reading of 1024 will therefore be 1.1V like @core_c mentioned in a previous posting. All analog inputs will use this reference (if not changed in the mean time ;-)) But if you have a stable LDO powering the Arduino there is nothing wrong with using the external (Vcc) reference. It's main use is avoiding external components when powering directly from batteries. (ref @Yveaux 's Vcc lib).

                                  1 Reply Last reply
                                  1
                                  • core_cC Offline
                                    core_cC Offline
                                    core_c
                                    wrote on last edited by
                                    #19

                                    The Arduino language reference says about "analogReference()": Configures the reference voltage used for analog input (i.e. the value used as the top of the input range).

                                    To me that means: Any reading you make, after setting the analogReference once, will use the same reference.
                                    So, if you are unsure, or if you want to be sure,.. Just set the analogReference before taking any new sample (for another sensor).

                                    If you have ANY other sample to make, from -some- device, and you know what maximum voltage it will return (that is: the voltage that is to be sampled),.. set the analogReference to the best fit, and then make the sample. Just be sure that the analogReference value can at least hold the maximum voltage to be sampled. In other words: If you have some device that outputs (say) 2 Volts, it will be incorrect to set the analogReference to 1.1V, because the input voltage could be higher than the reference voltage (and you can never sample values that exceed 1.1V).

                                    Once the sample has been taken (and you have your 10-bit sample), you just have to know what that sample represents.
                                    If, in your code, you never set the analogReference at all, the default input signal can be up to 5V. With a 10-bit sample resolution (1024 possible values), that means: 5 Volts / 1024 steps = 0.0048828125 Volt per sample-step. You can still sample voltages of 1 Volt,.. no problem.. but over an analogReference set to 5V, the maximum samplevalue is just a fifth of what could fit in 10 bits. In other words: The precision you measure will go down by a factor of 5.

                                    Because i know from the datasheet that the UVM30A will always produce a maximum voltage of 1 Volt, i set the analogReference to a value that fits best. It turns out that analogReference(INTERNAL) is quite good for sampling voltages that never exceed 1 Volt.

                                    In your case: If your battery reports greater voltages than 1.1V, simply set the analogReference to DEFAULT (5V) before taking a sample from the battery.

                                    I just checked the Arduino Reference: It seems not possible to put a voltage greater than 5V on the AREF pin. I have no experience with measuring battery voltages (yet). But i know the Arduino can be powered with more than 5V.
                                    What i want to say is: If you would have a sensor that outputs 2.3 Volts maximum, you could put 2.3V on the AREF pin of the Arduino, set analogReference(EXTERNAL), and make samples that are prefectly suited for that sensor.

                                    sundberg84S 1 Reply Last reply
                                    0
                                    • core_cC core_c

                                      The Arduino language reference says about "analogReference()": Configures the reference voltage used for analog input (i.e. the value used as the top of the input range).

                                      To me that means: Any reading you make, after setting the analogReference once, will use the same reference.
                                      So, if you are unsure, or if you want to be sure,.. Just set the analogReference before taking any new sample (for another sensor).

                                      If you have ANY other sample to make, from -some- device, and you know what maximum voltage it will return (that is: the voltage that is to be sampled),.. set the analogReference to the best fit, and then make the sample. Just be sure that the analogReference value can at least hold the maximum voltage to be sampled. In other words: If you have some device that outputs (say) 2 Volts, it will be incorrect to set the analogReference to 1.1V, because the input voltage could be higher than the reference voltage (and you can never sample values that exceed 1.1V).

                                      Once the sample has been taken (and you have your 10-bit sample), you just have to know what that sample represents.
                                      If, in your code, you never set the analogReference at all, the default input signal can be up to 5V. With a 10-bit sample resolution (1024 possible values), that means: 5 Volts / 1024 steps = 0.0048828125 Volt per sample-step. You can still sample voltages of 1 Volt,.. no problem.. but over an analogReference set to 5V, the maximum samplevalue is just a fifth of what could fit in 10 bits. In other words: The precision you measure will go down by a factor of 5.

                                      Because i know from the datasheet that the UVM30A will always produce a maximum voltage of 1 Volt, i set the analogReference to a value that fits best. It turns out that analogReference(INTERNAL) is quite good for sampling voltages that never exceed 1 Volt.

                                      In your case: If your battery reports greater voltages than 1.1V, simply set the analogReference to DEFAULT (5V) before taking a sample from the battery.

                                      I just checked the Arduino Reference: It seems not possible to put a voltage greater than 5V on the AREF pin. I have no experience with measuring battery voltages (yet). But i know the Arduino can be powered with more than 5V.
                                      What i want to say is: If you would have a sensor that outputs 2.3 Volts maximum, you could put 2.3V on the AREF pin of the Arduino, set analogReference(EXTERNAL), and make samples that are prefectly suited for that sensor.

                                      sundberg84S Offline
                                      sundberg84S Offline
                                      sundberg84
                                      Hardware Contributor
                                      wrote on last edited by
                                      #20

                                      @core_c - Woaw! Thank you! I really appreciate your help, effort and great explanation here!
                                      This made me understand how it works and now I understand what I made wrong. I will take my UV sensor down this week and upgrade it.

                                      Controller: Proxmox VM - Home Assistant
                                      MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
                                      MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
                                      RFLink GW - Arduino Mega + RFLink Shield, 433mhz

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                                      • sundberg84S Offline
                                        sundberg84S Offline
                                        sundberg84
                                        Hardware Contributor
                                        wrote on last edited by sundberg84
                                        #21

                                        I just wanted to update this post with my code and rebuild to this UV sensor thanks to @core_c!
                                        I also updated the box ;)

                                        0_1494874383421_1.jpg
                                        The Dallas temp sensor was never used in this project so please ignore...

                                        The node is build with a Slim Node. I could save some power by using a booster with VIn attached to D4. I keep the D4 low between sleeps. In sleep mode it consumes less than 10uA.

                                        The code:

                                        // Enable debug prints to serial monitor
                                        #define MY_DEBUG
                                        
                                        // Enable and select radio type attached
                                        #define MY_RADIO_NRF24                  //The radio we use!
                                        #define MY_NODE_ID 19                      //Fixed node ID
                                        #define MY_BAUD_RATE 9600           //Needs to be defined because standard for MySensors is 115200. This bootloader uses 9600!
                                        
                                        #include <SPI.h>
                                        #include <MySensors.h>
                                        #include <Vcc.h>
                                        
                                        //SketchInfo MySensors
                                        #define SKETCH_NAME "UV #19"                // Change to a fancy name you like
                                        #define SKETCH_VERSION "1.4"                // Your version  
                                        
                                        //Light
                                        #define CHILD_ID_LIGHT 1
                                        #define LIGHT_SENSOR_ANALOG_PIN A0
                                        #define SENSORS_POWER_PIN 4
                                        MyMessage light_Msg(CHILD_ID_LIGHT, V_LIGHT_LEVEL);
                                        
                                        //===================================================
                                        // UVM30A ultraviolet detector.
                                        //
                                        // Thanks to core_c @ mysensors.org for code and info!
                                        // The sensor's VCC is connected to +5V
                                        //
                                        // At first glance, the datasheet is not entirely making sense:
                                        //  "输出电压" translates to "Output voltage", with a value of: DC 0—1V.
                                        //  So the sensor will never output/measure the 2 highest values listed in the graph & table of the datasheet (1079 and 1170+).
                                        //  The datasheet explains it: "(对应 UV 指数 0-10)" translates to "(corresponding to UV index 0-10)".  Fair enough.
                                        //
                                        //  "测试精度" translates to: "Test accuracy", with a value of: ±1 UV INDEX
                                        //  That is not very accurate on a range 0-10. Example: if the real UV-index is 4, you could measure 3, or 5.
                                        //  For that reason we take an average of multiple samples, to get a better measurement.
                                        
                                        #define UV_PIN A1
                                        #define CHILD_ID_UV 0
                                        MyMessage uv_Msg(CHILD_ID_UV, V_UV);
                                        const int UV_threshold[12] = {50, 227, 318, 408, 503, 606, 696, 795, 881, 976, 1079, 1170}; // // The list of UV index thresholds in units of mV
                                        
                                        // The read value is a 10-bit value, ranging from 0 to 2^10-1 (0 to 1023).
                                        // The reference voltage on the input pin is set to 1.1V.
                                        // That voltage is spread out over the 1024 possible values of a sample.
                                        // So our achieved resolution equals (1.1 Volts / 1024) = 0.00107421875 Volt.
                                        // The UVM30A sensor datasheet lists all UV-index values according to measured milli-Volts.
                                        const float SAMPLE_TO_MV = (1.1 * 1000) / 1024; // mV per sample-resolution
                                        
                                        uint16_t UV_value;
                                        uint16_t UV_index;        // the UV index
                                        uint16_t UV_index_f;      // the fractional part of the UV index
                                        
                                        // Compiler directives for averiging the UV-sensor readings
                                        // (Change the values of UV_AVERAGE_T & UV_AVERAGE_N according to your own taste).
                                        #define UV_AVERAGE_T 4000 // Sample interval duration in milliseconds..  (1 <= T <= 60000)
                                        #define UV_AVERAGE_N 10   // ..During that interval, N samples are taken, and averaged.    (1 <= N <= 100, must be <>0)
                                        
                                        #if UV_AVERAGE_T < 1      // Sanity check. It must be dummy proof
                                        #define UV_AVERAGE_T 1
                                        #endif
                                        #if UV_AVERAGE_N < 1      // Sanity check. It must be dummy proof
                                        #define UV_AVERAGE_N 1    // This value must be <>0 at all times, because we divide by it
                                        #endif
                                        
                                        // calculate once, use many times in the loop()
                                        const float UV_AVERAGE_N_RP = 1.0 / UV_AVERAGE_N;
                                        const uint32_t UV_AVERAGE_D = UV_AVERAGE_T * UV_AVERAGE_N_RP;
                                        //===================================================
                                        
                                        //SleepTime
                                        unsigned long SLEEP_TIME = 600000; // Sleep time between reads (in milliseconds)
                                        
                                        //Battery
                                        const float VccMin   = 1.9;           // Minimum expected Vcc level, in Volts.
                                        const float VccMax   = 3.0;           // Maximum expected Vcc level, in Volts.
                                        const float VccCorrection = 1.0 / 1.0; // Measured Vcc by multimeter divided by reported Vcc
                                        
                                        Vcc vcc(VccCorrection);
                                        
                                        void presentation()  {
                                          // Send the sketch version information to the gateway and Controller
                                          sendSketchInfo(SKETCH_NAME, SKETCH_VERSION);
                                        
                                          // Register all sensors to gateway (they will be created as child devices)
                                          present(CHILD_ID_UV, S_UV);
                                          present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);
                                          
                                        }
                                        
                                        void setup()  {
                                        
                                          analogReference(INTERNAL);
                                        
                                          pinMode(SENSORS_POWER_PIN, OUTPUT);
                                          pinMode(UV_PIN, INPUT);
                                          pinMode(LIGHT_SENSOR_ANALOG_PIN, INPUT);
                                        
                                        }
                                        
                                        void loop()
                                        {
                                        
                                          digitalWrite(SENSORS_POWER_PIN, HIGH);  //Set power on digital pin for lightsensor.
                                          wait(500); //Wait 500ms to make sure lightsensor is powered and stable.
                                        
                                          processUV();   //Read UV
                                        
                                          readLightLevel();   //Read Light
                                        
                                          digitalWrite(SENSORS_POWER_PIN, LOW); // Set power for lightsensor off to save power.
                                        
                                          BatteryCalculation();
                                        
                                          //Sleep!
                                          sleep(SLEEP_TIME);
                                        }
                                        
                                        void readLightLevel()      {
                                          int lightLevel = (1023 - analogRead(LIGHT_SENSOR_ANALOG_PIN)) / 10.23; //To get a value ranging from 0 (dark) to 100 (bright).
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("Light: "); Serial.println(lightLevel);
                                        #endif
                                          send(light_Msg.set(lightLevel));
                                        
                                        }
                                        
                                        //===================================================
                                        // Process a UV measurement:
                                        // read an average value from the UV detector.
                                        // The average consists of N samples taken during a T milliseconds interval.
                                        //===================================================
                                        void processUV() {
                                          // Set the reference voltage for sampling
                                          // For our ATmega328 Nano: INTERNAL = 1.1V, DEFAULT = 5V
                                          // After using analogReference(), the first few samples may not be accurate (according to the Arduino language reference),
                                          // and that is why we read a few dummy samples before starting the actual measurement.
                                          // NOTE: If you change the next statement, beware to adjust the value of SAMPLE_TO_MV too.
                                        
                                          for (int i = 0; i < 10; i++) UV_value = analogRead(UV_PIN); // ignore the possibly inaccurate samplevalues.
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("UV raw values: [");
                                        #endif
                                          uint32_t average = 0;
                                          for (int i = 0; i < UV_AVERAGE_N; i++) {
                                        #ifdef MY_DEBUG
                                            UV_value = analogRead(UV_PIN);
                                            Serial.print(UV_value);  Serial.print(" ");
                                            average += UV_value;
                                        #else
                                            average += analogRead(UV_PIN);
                                        #endif
                                            delay(UV_AVERAGE_D);
                                          }
                                          UV_value = average * UV_AVERAGE_N_RP;
                                        #ifdef MY_DEBUG
                                          Serial.print("]    avg: ");  Serial.print(UV_value);
                                        #endif
                                        
                                          // We must convert sample-values into mV-values before we look up the UV-index.
                                          UV_value *= SAMPLE_TO_MV;
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("     mV: ");  Serial.print(UV_value);
                                        #endif
                                        
                                          // determine the UV index
                                          if (UV_value < UV_threshold[0]) {
                                            // too low value  or  invalid value (in case the sensor is wrongly connected it always returns 0)
                                            UV_index = 0;
                                            UV_index_f = 0;
                                          } else {
                                            for (UV_index = 11; UV_index > 0; UV_index--) {
                                              if (UV_value >= UV_threshold[UV_index]) break;
                                            }
                                            // calculate fractional part of the UV-index
                                            if (UV_index == 11) {
                                              // already at the maximum level; Displaying a fraction is meaningless
                                              UV_index_f = 0;
                                            } else {
                                              UV_index_f = map(UV_value, UV_threshold[UV_index], UV_threshold[UV_index + 1], 0, 9); // one decimal, so a number ranging 0 to 9
                                            }
                                          }
                                          float UV_index_float = UV_index + (UV_index_f * 0.1); // that is the same as /10
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("     UV index: ");  Serial.println(UV_index_float);
                                        #endif
                                        
                                          send(uv_Msg.set(UV_index_float, 1));
                                        
                                        }
                                        
                                          
                                        void BatteryCalculation()
                                        {
                                          float v = vcc.Read_Volts();
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("VCC = ");
                                          Serial.print(v);
                                          Serial.println(" Volts");
                                        #endif
                                          float p = vcc.Read_Perc(VccMin, VccMax);
                                        
                                        #ifdef MY_DEBUG
                                          Serial.print("VCC = ");
                                          Serial.print(p);
                                          Serial.println(" %");
                                        #endif
                                        
                                          sendBatteryLevel(p);
                                        
                                        }
                                        

                                        0_1494927947601_Schematics.jpg
                                        And offcourse the sensors analog output was connected to analog input of the atmega - forgot that in the schematics. UV=A0 and Light =A1

                                        Controller: Proxmox VM - Home Assistant
                                        MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
                                        MySensors GW: Arduino Uno - Gw Shield RFM69, 433mhz
                                        RFLink GW - Arduino Mega + RFLink Shield, 433mhz

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                                        • core_cC Offline
                                          core_cC Offline
                                          core_c
                                          wrote on last edited by
                                          #22

                                          cool!..
                                          I like that slim node. compact.
                                          It's even more fun that it's all functioning. (y)

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