Netduino 3 Wifi pollution Sensor Part 1

I am working on a Netduino 3 Wifi based version for my original concept as a STEM project for high school students. I wanted to be able to upload data to a Microsoft Azure Eventhub or other HTTPS secured RESTful endpoint (e.g. xivelyIOT) to show how to build a securable solution. This meant a Netduino 3 Wifi device with the TI C3100 which does all the crypto processing was necessary.

The aim was to (over a number of blog posts) build a plug ‘n play box that initially was for measuring airborne particulates and then overtime add more sensors e.g. atmospheric gas concentrations, (Grove multichannel gas sensor), an accelerometer for earthquake early warning/monitoring (Grove 3-Axis Digital Accelerometer) etc.

Netduino 3 Wifi based pollution sensor

Bill of materials for prototype as at (October 2015)

  • Netduino 3 Wifi USD69.95
  • Seeedstudio Grove base shield V2 USD8.90
  • Seeedstudio Grove smart dust sensor USD16.95
  • Seeedstudio Grove Temperature & Humidity Sensor pro USD14.90
  • Seeedstudio ABS outdoor waterproof case USD1.65
  • Seeedstudio Grove 4 pin female to Grove 4 pin conversion cable USD3.90
  • Seeedstudio Grove 4 pin buckled 5CM cabed USD1.90

After the first assembly I have realised the box is a bit small. There is not a lot of clearance around the Netduino board (largely due to the go!bus connectors on the end making it a bit larger than a standard *duino board) and the space for additional sensors is limited so I will need to source a larger enclosure.

The dust sensor doesn’t come with a cable so I used the conversion cable instead. NOTE – The pins on the sensor are numbered right->Left rather than left->right.

The first step is to get the temperature and humidity sensor working with my driver code, then adapt the Seeedstudio Grove-Dust sensor code for the dual outputs of the SM-PWM-01 device.

According to the SM-PWM-01A device datasheet The P1 output is for small particles < 1uM (smoke) and P2 output is for large particles > 2uM (dust). The temperature & humidity sensor is included in the first iteration as other researchers have indicated that humidity levels can impact on the accuracy of optical particle counters.

Then, once the sensors are working as expected I will integrate a cut back version of the AMQPNetLite code and configuration storage code I wrote for my Netduino 3 wifi Azure EventHub Field Gateway.

Netduino pollution Monitor V0.1

As part of a project for Sensing City I had been helping with the evaluation of  PM2.5/PM10 sensors for monitoring atmospheric pollution levels. For my DIY IoT projects I use the SeeedStudio Grove system which has a couple of dust sensors. The Grove Dust Sensor which is based on a Shinyei Model PPD42 Particle Sensor looked like a cost effective option.

Seeedstudio Grove Dust Sensor

Seeedstudio Grove Dust Sensor

Bill of Materials for my engineering proof of concept (Prices as at June 2015)

I initially got the sensor running with one of my Arduino Uno R3  devices using the software from the seeedstudio wiki and the ratio values returned by my Netduino Plus 2 code (see below) look comparable. I have purchased a couple of extra dust sensors so I can run the Arduino & Netduino devices side by side. I am also trying to source a professional air quality monitor so I can see how reliable my results are

The thread ” (0x2) has exited with code 0 (0x0).

Ratio 0.012

Ratio 0.012

Ratio 0.020

Ratio 0.008

Ratio 0.031

Ratio 0.014

Ratio 0.028

Ratio 0.012

Ratio 0.013

Ratio 0.018

public class Program
private static long pulseStartTicks = 0;
private static long durationPulseTicksTotal = 0;
readonly static TimeSpan durationSample = new TimeSpan(0, 0, 0, 30);
readonly static TimeSpan durationWaitForBeforeFirstSample = new TimeSpan(0, 0, 0, 30);

public static void Main()
InterruptPort sensor = new InterruptPort(Pins.GPIO_PIN_D8, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
sensor.OnInterrupt += sensor_OnInterrupt;

Timer sampleTimer = new Timer(SampleTimerProc, null, durationWaitForBeforeFirstSample, durationSample);


static void sensor_OnInterrupt(uint data1, uint data2, DateTime time)
if (data2 == 1)
long pulseDuration = time.Ticks - pulseStartTicks;

durationPulseTicksTotal += pulseDuration;
pulseStartTicks = time.Ticks;

static void SampleTimerProc(object status)
double ratio = durationPulseTicksTotal / (double)durationSample.Ticks ;
durationPulseTicksTotal = 0;

Debug.Print("Ratio " + ratio.ToString("F3"));

Next steps will be, adding handling for edges cases, converting the ratio into a particle concentration per litre or 0.1 cubic feet, selecting a weather proof enclosure, smoothing/filtering the raw measurements, and uploading the values to Xively for presentation and storage.