Disclaimer: This project is still a work in progress! I adopted the project from a group of undergrad students that previously attended UMass Amherst and have since graduated. The function of this particular air sensor is to take measurements of air temperature, humidity, and dust particulate (in parts-per million). Here is a link for the sensor I was handed last year:
Originally, the sensor would take these measurements and write the data to a SD card. What I am attempting to add to this project is to give it the ability to transmit real time data to a website, as well as visualizing the data through plotting it on a graph. To do this, I am reassembling the sensor using an ESP8266 wifi shield instead of the Arduino Pro Micro so that it can connect to wifi. In addition, I have set up a Thingspeak.com account which receives the data transmitted from the sensor and plots it automatically.
So far, I have run into a few problems. The first being that the ESP8266 has digital input pins that only allow an input of 0-1V which differs from the Arduino input pins. To overcome this I had to add a resistor into the circuit between the 5V and the output of the DHT22 temperature and humidity sensor. Now, I am approaching a similar problem with the dust sensor. I am having trouble deciding the magnitude of the resistor I need to place between the 5V and output pin of the Shinyei PPD42NJ Dust Sensor.