I have few sensors. Temperature sensor (DHT22), flow rate sensor, rpm optical tachometer sensor and a rgb led. I want to use adafruit IO to get values of these sensors and change the colour of the led. Most of the tutorials online use a builtin WiFi module but I want to do it separately. please guide me how to do it? I am going to use esp8266 and arduino nano.
Use tutorial for the esp8266 module to connect to Adafruit IO (MQTT). Then code the exchange of the data between Nano and esp8266 using Serial communication. (You can test the Serial communication by sending lines to esp8266 from Serial Monitor and of course by showing the prints from the Nano.)
Consider using only esp8266 dev board like Wemos D1 mini or NodeMCU.