Your first circuit: blink an LED

The “hello world” of hardware — go from a bare breadboard to a blinking LED in five minutes, and learn the build–test–fix loop behind everything else.

Every maker starts somewhere, and there’s no better first project than blinking an LED. In a few minutes it teaches you the breadboard, polarity, current-limiting resistors, and the satisfying loop of build → test → fix that underpins every project after it.

What you’ll need

A solderless breadboard
One LED — any colour (we used a 5 mm green)
A 220 Ω resistor to limit current
A microcontroller (Arduino, ESP32) or a 3 V coin cell
Two jumper wires

Mind the polarity

An LED only conducts one way. The longer leg is positive (the anode); the flat edge on the rim marks the negative side (the cathode). Backwards, it simply won’t light.

Wire it up

Build the loop one connection at a time — test after each:

Sit the LED across the centre channel of the breadboard so its two legs are on different rows.
Connect the 220 Ω resistor from the LED’s anode row to a power rail.
Run a jumper from the cathode row to ground (GND).
Connect power — the LED lights. If it doesn’t, flip the LED around.

Make it blink

Static light is good; blinking is better. Drive the LED from a microcontroller pin instead of the power rail and toggle it in a loop:

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);
}

void loop() {
  digitalWrite(LED, HIGH);   // on
  delay(500);
  digitalWrite(LED, LOW);    // off
  delay(500);
}

Move the resistor + LED so the anode connects to pin 13 instead of the always-on rail, upload the sketch, and it blinks once a second. Change the delay() values to change the rhythm.

The moment that LED first blinks, you’ve crossed the line from reading about electronics to making them.

Where to next

From here the path opens up fast — drive several LEDs, fade one with analogWrite(), or read a button and react. When you get stuck (and you will), the forum is the place to ask.