Archives: Tutorials

The Arduino Uno is a small board built around an ATmega328P microcontroller. It runs one program at a time, from the moment it receives power until it loses it, and it gives you pins that can switch things on and...

You have uploaded a sketch and watched an LED blink. This explains what was actually happening, because almost every confusing moment later comes from a wrong mental picture of it.

Enough electrical theory to stop you destroying parts, and no more. Three quantities, one equation, and the two calculations you will actually do: choosing a resistor for an LED, and working out whether a pin can drive something.

A kit arrives as a bag of small objects, most of them unlabelled in any obvious way. This is how to work out what each one is and which way round it goes.

Which holes in a breadboard are joined to which, how to build on one without creating shorts, and the handful of mistakes that account for most "it was working yesterday" faults.

A multimeter answers the question every stuck project comes down to: is this wire actually connected, and is the voltage where I think it is?

The Serial Monitor is the only window you have into a running sketch. A board gives no error message when something is wrong; it simply does the wrong thing quietly. Printing to serial is how you find out why.

Everything works on the bench with a USB cable. Then you add a servo, or unplug the laptop, and it stops. This covers the ways to power an Uno, how much current you actually have, and the three mistakes that...

What a library is, the two ways to install one, and how to avoid the version problems that make a sketch work on one computer and fail on another.

An LED is a diode that gives off light when current passes through it the right way. Two things follow from that, and they are the whole of this tutorial: it only works one way round, and it needs something...

An RGB LED is three LEDs in one clear package, one red, one green, one blue, sharing a single common leg. Drive them at different brightnesses and the eye blends the result into one colour.

The traffic light module puts a red, a yellow and a green LED on one small board with a shared ground connection, so three separate outputs can be wired with four jumper wires instead of six wires and three loose...

An active buzzer contains its own oscillator. Give it a steady voltage and it sounds at a pitch the manufacturer chose. Take the voltage away and it stops.

A tactile push button is a switch that connects two contacts while you hold it down and disconnects them when you let go. That is all it does, and it is the foundation of every input a project will ever...

A tilt sensor is a switch that is operated by gravity instead of a finger. Inside the small metal cylinder is a rolling ball; tip the sensor past a certain angle and the ball rolls onto two contacts and closes...

A potentiometer is a resistor with a movable contact. Turning the shaft slides that contact along the resistive track, so the voltage at the middle pin varies smoothly between the voltages at the two ends.

A light-dependent resistor is a resistor whose value falls as light falls on it. In the dark it might be hundreds of kilohms; in bright light, a few hundred ohms.

A passive buzzer is a small sounder with no electronics inside. It makes no sound on its own: whatever frequency you feed it is the pitch you hear. That is the difference between the two kinds of buzzer Siratek sells,...

By now you have used all four of them: digitalRead(), digitalWrite(), analogRead() and analogWrite(). This page is about what those words actually mean on an Uno, because the naming is misleading in two places and both of them cause real...

A digital pin has two states, on and off. Yet analogWrite() dims an LED and slows a motor. This explains how, which pins can do it, and the three places it behaves differently from what you would expect.

How to get an answer out of a forty-page PDF in two minutes.

delay() is the first thing every Arduino tutorial teaches and the first thing every real project has to stop using. This explains why, and gives you the pattern that replaces it.

One press, three counts. This explains why a mechanical switch does that, and how to fix it without blocking the rest of your program.

An Uno has fourteen digital pins. A character display can want six of them, and that is before you add a clock, a sensor and a display driver.