Archives: Tutorials

An ESP32 is an Arduino-compatible board with Wi-Fi and Bluetooth built into the chip. It is faster than an Uno by about fifteen times, has over two hundred times the RAM, and costs less than a Mega.

The board becomes a small web server on your network. Type its address into a phone and you get a page showing a sensor reading, with buttons that switch something on and off.

The web server tutorial made the board wait for someone to ask. MQTT turns that round: the board publishes a reading whenever it has one, and anything interested subscribes and receives it.

Wi-Fi, in a board that costs less than an ESP32 and does most of what one does. The ESP8266 came first; the ESP32 is its successor.

An ESP32 with a camera and a micro SD slot, for about the price of a sensor. It serves a live video stream to a browser, takes still images to a card, and does face detection on the board itself.

An HC-05 makes a wireless serial link. Pair a phone or a laptop with it, open a terminal app, and whatever you type arrives at the Arduino exactly as if it came down the USB cable. Whatever the Arduino prints...

Two Arduinos talking to each other directly, over 2.4 GHz, with no network, no router and no internet. One sends a packet, the other receives it, and the radio handles acknowledgement and retries by itself.

The cheapest radio link there is. A transmitter the size of a postage stamp, a receiver slightly bigger, and a few lines of code gets a message from one Arduino to another across a building.

The spiral on the board is an antenna. It broadcasts a short-range field at 13.56 MHz, and a card held near it harvests enough energy from that field to power its own chip and answer back. The card has no...

A GPS receiver listens for signals from satellites twenty thousand kilometres up, works out how long each took to arrive, and from that calculates where it is. It then reports position, time, speed and heading as lines of text on...

A mobile phone module. Put a SIM in it and an Arduino can send a text message from anywhere with coverage, with no Wi-Fi, no router and no internet.

An optical fingerprint sensor with a processor of its own. It photographs a finger, extracts the features, and stores or compares them on the module, sending the Arduino nothing more than "this is number 7" or "no match".

A working pedestrian crossing. The traffic light sits on green. Press the button and nothing happens for a moment, then amber, then red, a beep while the crossing is clear, and back to green after a sensible pause.

A small screen showing temperature, humidity and air pressure, with a three-hour pressure trend that tells you whether the weather is turning.

A box you leave somewhere for a week. It records a temperature every minute with a real date and time against it, and when you come back the card opens in a spreadsheet and draws a graph.

A clock that shows the time on a 16x2 display, lets you set an alarm with buttons, and wakes you with a tune. Press to snooze, hold to stop.

A small box you put in a room. It measures temperature and humidity, publishes them over Wi-Fi every minute, and tells you when it stops.

A plant that waters itself. A probe in the pot, a pump in a bucket, and a sketch that decides when the soil is dry enough to do something about it.

A box that watches the air near an LPG cylinder, sounds an alarm when the level rises, latches until somebody acknowledges it, switches on a fan, and tells you plainly when it cannot be trusted.

A cabinet that opens when you present a card. A reader on the outside, a solenoid latch on the inside, a release button, and a list of accepted cards that survives being unplugged — with a master card that adds...

A robot that follows a line of black tape across the floor. Four sensors looking down, two geared motors, and a sketch that turns "the line is slightly to my left" into "slow the left wheel".