Update README.md

README.md

@@ -1,2 +1,24 @@
 # airQualityBox
 Air Quality Measurement sketch for Arduino Mega with Adafruit TFT touch screen and DSM501A dust sensor
+
+## Building the Box
+To build the box, I partially followed this instructions:
+https://projetsdiy.fr/calculer-indice-qualite-air-iaq-ciqa-iqa-dsm501-arduino-esp8266/
+
+The changes to that design I made where:
+- I used an Arduino Mega instead of the ESP8266 used in that example
+- I added a TFT screen from Adafruit and all the logic to present the data recovered using the proposed sketch
+
+Once the dust sensor (http://www.samyoungsnc.com/products/3-1%20Specification%20DSM501.pdf) is connected to GND, 5v and digital inputs 30 and 40, after solder close the pins 11, 12 & 13 of your TFT screen as explained here https://learn.adafruit.com/adafruit-2-8-tft-touch-shield-v2/connecting (to allow it working with Arduino Mega) and plugged it into the arduino Mega, then you just need to power it with a powerbank and place the dust sensor in vertical position and let it work. It's important to keep the sensor out from any artificial air current (like a fan). The dust sensor will heat inside to create a small air current to make the dust go through the optical sensor. The sketch will keep a record of the last measurements, splitting the results with the following distribution:
+
+- Upper side of the screen - Average
+Average for the last X measurements. Colors will vary depending on the average AQI obtained
+
+- Lower side of the screen - Last instant measure
+  - Left small window representing the values for PM25 (concentration and AQI) and background color according to the AQI
+
+  - Right small windows representing the values for PM10 (concentration and AQI) and background color according to the AQI
+
+  - Global AQI measurement. For the rest of the lower part of the screen, the color will be the global AQI (this is, the worse value between PM25 and PM10), and a message accordingly (excellent, bon, moyen, mauvais, dangereux)
+
+Enjoy, measure and improve this sketch! and please, if you do so, let me know!