Archives: Tutorials

Sixty-four LEDs in an eight by eight grid, driven by a MAX7219, which is a chip built to do exactly the multiplexing you did by hand on the seven-segment display.

A hobby servo is a small geared motor with a position sensor and a control circuit inside. You do not tell it to turn; you tell it where to be, and it drives itself there and holds.

The same servo as the SG90, built properly. Same size, same three wires, same control signal, same library, same code — and metal gears, ball bearings and about a third more weight.

An L298N module is an H-bridge: a switching arrangement that lets a small control signal decide which way current flows through a motor, and therefore which way the motor turns. The board carries two of them, so it drives two...

A motor that moves in counted steps instead of simply turning. Tell it to go four thousand and ninety-six steps and it goes exactly once round — no encoder, no feedback, no trim.

A small DC motor with a plastic gearbox on the front and a rubber wheel that pushes on. The gearbox trades the motor's uselessly high speed for the torque needed to actually move something.

A relay is a mechanical switch operated by an electromagnet. A small current through the coil pulls a set of contacts together, and those contacts can carry far more current than the coil ever touches, on a circuit that has...

Two relays on one board, so one Arduino can switch two separate loads. A fan and a lamp, a pump and an alarm, a heater and a light.

A small brushless pump that sits in the water it moves. Drop it in a tank, run a tube from its outlet, and it will lift water three metres.

A small metal latch with a sliding bolt and a coil behind it. Energise the coil and the bolt retracts; remove the power and a spring pushes it back out.

Sixteen keys on a thin adhesive-backed membrane: digits 0 to 9, *, #, and A to D. It is how a project asks for a PIN, a temperature, a menu choice, anything that needs more than a button or two.

A thumbstick like the ones on a games controller. Inside are two 10 kilohm potentiometers, one turned by movement left and right, one by movement up and down, plus a momentary switch under the stick that closes when you press...

A small three-pin receiver that listens for the infrared flashes a remote control sends, and a 21-button remote to send them. Point, press, and your sketch gets a number.

A real time clock: a chip that knows the date and time and keeps counting through power cuts, on a coin cell, for years.

A micro SD card socket on a small board, so an Arduino can write files. Readings go to a card, the card goes into a computer, and you open the result in a spreadsheet.

Every tutorial in this library so far has assumed an Uno, because it is the right board to learn on. It is not the right board for everything you will build next.

An Uno's pins swing to 5 V. An ESP32's, a BMP280's and an RC522's swing to 3.3 V, and their inputs are not built to survive 5 V.

Powering Your Project was about the Arduino's own sockets. This is about building the supply yourself: when a project runs from a battery, needs 3.3 V as well as 5, or has to last a season outdoors.

Take the chip out of the Uno, put it on a breadboard with two or three other components, and your sketch runs exactly as before.

Eight pins, five of them usable, 8 KB of flash and 512 bytes of RAM, in a chip the size of a fingernail.

Everything so far has worked by checking: loop() runs round, reads a pin, and decides. That is fine while the loop is quick, and it starts to fail when the loop has real work in it.

A project on your bench has you watching it. A project in a greenhouse, a tank or a workshop does not, and the difference is not a small one: a fault you would have noticed in seconds can run for...

Every tutorial in this library ends with a troubleshooting table for that part. This page is the one you reach for when you do not know which part is at fault, or when the symptom is the whole project rather...

A sketch that compiled and worked last year will not necessarily compile today, on the same computer, with the same code. Nothing in your file changed. A library did.