Pollution Sensor

You’re right. Because pure sensor uses inverted and waveshare adapter inverts it. So, I have this code:

GP2Y1010AU0F to masakra. Nie nadaje się do skutecznego pomiaru. 

I decided to move all calculations & aproximations from arduino code to Thingspeak service. Sensor will be only responsible of uploading raw data to Thingspeak service. This significantly reduces my efforts to upoad new software to sensor module.

Here are functions written in Matlab language that is used by Thingspeak to perform data processing and converting PM2.5 levels to CAQI Euro standard.

Formula to calculate CAQI is described on Wikipedia. https://en.wikipedia.org/wiki/Air_quality_index#Europe

Unfortunately there are only few examples realized in code on the internet.

I succed to calibrate my sensor using nearest official sensors. Sensor real time data is published on my open Thingspeak channel.

I suceed to build my second sensor. This time it is more expensive. PMS5003 is not analog sensor like Sharp GP2Y1010AU0F.  PMS5003 is laser-based sensor with built in microcontroller that performs all required calculations and sends digital data messages to its TXD pin5. You could use other sensors like  PMS6003,  PMS7003 and even older ones like PMS1003 or PMS3003. They all could be connected in the same way, just pay attention at message length in the source code (If I am not wrong PMS5003/6003/7003 uses 32byte long messages but PMS3003 uses 24bit).

My first workingh prototype was connected to NodeMCU by only 3 wires: +5V, GND and RX. It was enough to activate sensor and start receiving some data on RX line. 

PMS5003 requres +5V but data lines should be connected to 3.3V levels which is used by NodeMCU 

* Be aware if you would like to connect PMS5003 to Arduino you should use 5<=>3.3v logic level converter.

 Also please note that some NodeMCU versions dont support 5V on Vin pin. In my case I have chinese clone LoLin NodeMCU V3 board that has 5V on reserved pins. The simpliest test is to connect power to PMS5003  PIN1 and PIN2 and you should hear a fan noise immediately.

I’ve built my 1st prototype and succesfully programmed using article from DFRobot: https://www.dfrobot.com/wiki/index.php/PM2.5_laser_dust_sensor_SKU:SEN0177

Although their sample code is for Arduino it works fine on NodeMCU too.

Following diagram has some additional pin connected to digital output but it is not requred for prototype. I used it to force PMS5003 to sleep and save a bit power between measurements. I will describe ti in my next post, together with my source code.

Usefull links:

https://www.dfrobot.com/wiki/index.php/PM2.5_laser_dust_sensor_SKU:SEN0177

http://aqicn.org/sensor/pms5003-7003/

I have been looking for a simple solution to connect pollution sensor to the network and push data to colud for aggregation & visualisation. Arduino is good if you have USB connection to some PC that is connected to internet. But unfortunately there are no simple (and inexpensive) solutions for Arduino if you like to have autonomous device and sporadicaly connect to internet by WIFI to post sensor data. My first solution was  ESP8266 WIFI chipset connected to Arduino:

Trying to connect Arduino to WIFI using ESP8266 I accidently found better solution. NodeMCU board - Arduino like microcontroller based on ESP8266 chipset.

Great advantage of NodeMCU is that you could program it with onboard USB bridge using Arduino IDE and there are several frameworks that allow you to control chipset from your Android or iOS device and push data directly from microcontroller to the cloud services using HTTP protocol.

For example you can easily create Android application using Blynk IoT service: http://www.blynk.cc/

Here are several resources about how to program NodeMCU using Arduino IDE:

http://henrysbench.capnfatz.com/henrys-bench/arduino-projects-tips-and-more/arduino-esp8266-lolin-nodemcu-getting-started/

https://www.youtube.com/watch?v=tMRpYmDgkL0

http://www.instructables.com/id/Quick-Start-to-Nodemcu-ESP8266-on-Arduino-IDE/

I’ve bought more precise (and 5x-times expensive) sensor - Plantower PMS 5003. Soon I will make a post about how to connect it to arduino and some comparisons with sharp sensor.

Interresting article about subject: https://publiclab.org/wiki/optical-pm

A sensor and a focused light (sometimes a laser) sit at an angle to each other. As a particle passes in front of the light, some light is reflected towards the sensor. The sensor registers a pulse for as long as the particle reflects light to the sensor. If the air is moving at a consistent speed, the length of this pulse can be used to estimate the particle’s diameter...

I would like to read data about PM2.5 levels from Arduino and proceed on my home PC. Then it will be possible to generate charts, send notifications and calculate pollution statistic.

As you know it is not a problem to read serial data from Arduino IDE. But how to proceed it?

I decided to try one of modern popular and simple to use technologies - Node JS. It is JavaScript based framework that dones’t require Web Browser to execute Javascript on computer and it has a lot of libraries to work with web serices as well as communication with local peripheral devices connected to USB or serial ports.

It took me 20 minutes to download & install Node JS software from https://nodejs.org/ and run my first program. It is able to read and print serial data from Arduino.

1: var SerialPort = require('serialport'); 2: var serialport = new SerialPort('COM3'); 3: 4: serialport.on('open', function(){ 5:   console.log('Serial Port Opend'); 6:   serialport.on('data', function(data){ 7:   console.log(data.toString('utf8')); 8:   }); 9: });

First of all you need to install “serialport” library that is not included to Node JS package.

Run Node.js command prompt and run 

npm install serialport

After that you could call your application. I stored scipt to ardu_serial.js file. So, to call it as application just run it from Node.js console:

1: node ardu_serial.js

If take to consideration, that sensor uses reflected IR light from dust particles to measure air quality. We can make automatic calibration for cleanest air if sample data without flashing IR LED. No light/reflection means cleanest air.

But unfortunately when I tried to measure dust level without IR, I’ve got maximum dust value, like I have by putting some stick inside the hole :(

Finally I found and fixed my mistake in formulas. I’ve used incorrect axes in linear equation y = ax + b 

or: voltage = a*dust + b

Fixed:  dust = (voltage - b) / a

Hi, sorry for late response. It might work fine, but anyway you need to calibrate it for your voltage. Try to use this article: http://www.pocketmagic.net/sharp-gp2y1010-dust-sensor/

I’ve performed some measurements of output signan to ILED and found that all Arduino programs that I’ve found on internet have incorrect sample timing.

Typical code is:

 digitalWrite(PIN_LED, HIGH); // power on the LED

 delayMicroseconds(280);

 int analogData = analogRead(SENSOR_PIN);

 delayMicroseconds(40);

 digitalWrite(PIN_LED, LOW); // power off the LED

 delayMicroseconds(9680);

  280 + 40 + 9680 = 10000 

Excelent according to sensor specification

But no one takes to consideration that analogRead is slow operation, that lasts for about 10 microseconds. Other operations also takes some time.

So, I’ve decided to check real pulse timings.

I’ve had Salae Logic usb digital osciloscope, that can measure impulse lenght, and I’ve performed several tests.

That code above gives following picture in analyzer program window:

Total period T = 10.28ms

ILED light time = 0.4391ms instead 0.32

As you see it is more than expected. If we calculate how much takes analogRead = 10280 - 10000 = 280 microseconds.

So I’ve decided to remove 40 microseconds delay befor switch-off

digitalWrite(PIN_LED, HIGH); // power on the LED

delayMicroseconds(280);

int analogData = analogRead(SENSOR_PIN);

delayMicroseconds(40);

digitalWrite(PIN_LED, LOW); // power off the LED

delayMicroseconds(9680);

New walues are slightly better

Total period T = 10.19ms

ILED light time = 0.398 ms instead 0.32

Finaly, to calculate how much time is needed to switch-on/off ILED I’ve calculated following code:

digitalWrite(PIN_LED, LOW); // power off the LED

digitalWrite(PIN_LED, HIGH); // power on the LED

digitalWrite(PIN_LED, LW); // power off the LED

So, each operation takes 0.05ms

After all I’ve decreased samples sleep delay time to  9500 to have period time close to 10ms.

I’ve decided to add LCD dispaly to the project to show calculated value. In this case dust sensor will be autonomous. I've used 16x2 LCD display HD44780. To handle display printing I've used LiquidCrystal library. By default enabled only serial printing: #define SERIAL_PRINT true. If you would like to enable LCD printing please set #define LCD_PRINT true.

Since I've got a lot of noise during measurements, I decided to filter it out from final results. It is performed by calculating median over 5 samples, and from that value is removed maximum & minimum results (avgDust - maxDust - minDust) / (SAMPLES_PER_COMP - 2). But this is not the end. To display data more smoothly I've added one more filter - stack[100] to store already filtered data and calculate median once more, over 100 samples.

I still was not happy with result's that I've achieved. My sensor was able to show hazardous concentrations of dust, but calculated dust veight values ug/m3 was far from data that I've got from official sensors, published in internet. I've found very usefull article about similar project, performed by Matthias Budde, Mathias Busse, and Michael Beigl from Karlsruhe Institute of Technology http://www.teco.edu/~budde/publications/MUM2013_budde.pdf

I was on the right direction. Now I need to perform additional calibration and include ambient temperature to calculations.

  I've fixed several bugs and improved dust calculation formulas. All code sources and last chnages please check at: https://github.com/vlytsus/arduinosensor