How things talk
Smart things need to send messages: to the brain, to each other and to your phone. Some use wires, and some talk through the air with invisible radio waves.
Talking through wires
Inside a project, sensors talk to the brain through wires. Some sensors need just one signal wire. Others share two wires called I2C, like several people taking turns on one phone line, each with their own name (an address).
Talking through the air
| Way to talk | How far | Like… | Good for |
|---|---|---|---|
| WiFi | Inside a house | Talking in a room | Sending data to the internet |
| Bluetooth | About 10 metres | Whispering to a friend | Controlling things from a nearby phone |
| Infrared (IR) | Across a room, in a straight line | Flashing a torch signal | TV-remote control |
| LoRa | Several kilometres | Shouting across a valley | Farms and villages without WiFi |
| Mobile network (4G / GSM) | Anywhere with phone signal | Making a phone call | Trackers and SMS alerts |
Messages need a language
Devices agree on a language, called a protocol, so they understand each other. A popular IoT language is MQTT. It works like a school notice board: one device pins a message on a topic, such as "garden/soil", and every device that follows that topic reads it.