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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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  • E edweather

    Hello,

    I just started with arduino and mysensors and I would like to share my first steps (re)building my broken uv-sensor.
    I bought the orignal TS704 UV sensor about two years ago. A few weeks ago it stopped sending acurate UV readings. On lots of placesa on the internet there are complaints abouts this sensor and the relative short lifetime. Main reason I think is water leakage in the sensor. I didn't want to buy a new one because the problem would be back within 2 years and they are realy expensive at the moment (about €70).
    Then I found the mysensors site in my quest to fix my broken device and my first sensor project was born!
    I ordered the pieces I needed and started to build.
    First the gateway, connected to domoticz which was easy as I connected it directly to the raspberry pi using the pigatewayserial software. Antenna directly connected to the Pi so no Arduino board needed!.
    Changed tty TTY_NAME := /dev/ttyMySensorsGateway to tty
    TTY_NAME := /dev/ttyUSB30 in the makefile because Domoticz cannot use ttyMySensorsGateway.
    After that It was easy to add the serialgateway to Domoticz!

    upload-e224b990-a645-4097-a509-02e4a7273ae3

    my list:
    Arduino pro mini 8mb 3v
    UVM-30a UV sensor
    NRF24L01+ 2.4GHz Wireless Transceiver
    TS704 UV sensor housing including 2xAA batery compartment
    Used the default sketch with pin A0 instead of pin 3 (http://www.mysensors.org/build/uv)

    On my breadboard I had things up and running quite easy but the readings were strange. Even at night there was UV light measured. The problem was a mismatch between the intructions on this website about the out pin to use and the one mentioned in the sketch. Sketch showed pin A0 as OUT but website showed pin 3 as OUT.
    @hek has confirmed that A0 is the correct pin. Website will be updated. (is updated now)
    I was mislead because with nothing connected to pin A0 it still gives you output data.
    It's also possible to use 3V for the UVM-30A instead of only 5volt I found this in the spec sheet.

    So the stepup from 3 to 5v is not needed I think?

    To get things in the housing I had to desolder the main piece from the UV sensor. Things have gone wrong from here because after that the sensor did not work anymore. Probably fried the sensor?! New one is on its way.
    So I must think of another way to get the sensor in place at the top of the housing. There not enough place so I must be creative and not destroying another sensor!

    I also would like to share a short piece of code I found to test the uv sensors output. This way you don't need to attach all the radio wires to see if the sensor is working.

    /*

    This Sample code is for testing the UV Sensor .

    #Connection:
    VCC-5V
    GND-GND
    OUT-Analog pin 0
    */

    void setup()
    {
    Serial.begin(9600);// open serial port, set the baud rate to 9600 bps
    }
    void loop()
    {
    int sensorValue;
    sensorValue = analogRead(0);//connect UV sensors to Analog 0
    Serial.println(sensorValue);//print the value to serial
    delay(200);
    }

    The pieces on the table:
    IMG_0353.JPG

    New sensor arrived and bought a 15W soldering iron.

    Puting things together and make some room for the sensor board

    20150526_190923284_iOS.jpg

    20150529_181320010_iOS.jpg

    20150613_133448340_iOS.jpg

    After everthing was put in place the sensor went outside for testing.
    For reference I also used a nearby UV sensor via Weather Underground.

    20150615_150304000_iOS.png

    At first everything looked fine but it seems that the measurements from my sensor are to low.
    I removed the sensor and did some testing with the above sketch to measure the output voltage on 3.3v and 5v but the results were the samen and to low.
    Does anyone know what can cause this low measurement ? checked the wires. checked the sketch. replaced the arduino board.
    Another broken sensor?

    M Offline
    M Offline
    Mediacj
    wrote on last edited by
    #2

    @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 1 Reply Last reply
    0
    • 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;

            1 Reply Last reply
            0
            • 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
              0
              • 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!

                            Controller: Proxmox VM - Home Assistant
                            MySensors GW: Arduino Uno - W5100 Ethernet, Gw Shield Nrf24l01+ 2,4Ghz
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                            1 Reply Last reply
                            0
                            • 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?

                              1 Reply Last reply
                              0
                              • 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).

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                                    • 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
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                                      • 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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