Using a breadboard

Learn

What you’ll learn

• How the holes in a breadboard are connected
• How to use the power rails
• The most common breadboard mistakes

What is a breadboard?

A breadboard is a plastic board full of holes with metal clips underneath. Push wires and component legs in, and the clips connect them. No soldering, so you can build, test and change circuits in seconds.

How the holes connect

  +  −                                        +  −
  ●  ●    a b c d e     f g h i j             ●  ●
  ●  ●  1 ●─●─●─●─●     ●─●─●─●─●             ●  ●
  ●  ●  2 ●─●─●─●─●     ●─●─●─●─●             ●  ●
  ●  ●  3 ●─●─●─●─●  ┃  ●─●─●─●─●             ●  ●
  │  │    (rows of 5)  gap  (rows of 5)        │  │
  rails run the full length                   rails

• Terminal strips (the middle): each short row of 5 holes (a–e, or f–j) is connected. Row 1 a–e is one connection; row 1 f–j is a different one.
• The centre gap separates the two halves. Chips (ICs) straddle this gap so each pin gets its own row.
• Power rails (the long edges): each long line marked + or − is connected along its length. Use them for 5 V and GND.

Caution

On some long breadboards the power rails are split in the middle. Look for a break in the red/blue line, and bridge it with a short wire if needed.

Building on a breadboard

1. Connect your supply’s + to the red + rail and −/GND to the blue − rail.
2. Place components so their legs are in different rows, unless you want them connected.
3. Use jumper wires to link rows together and to the rails.
4. Colour code: red = power, black = ground, other colours for signals.

Common mistakes

Mistake	Result	Fix
Both legs of a part in the same row	Part is shorted out, does nothing	Turn it so legs are in different rows
Forgot to connect GND	Nothing works	Every circuit needs a return path
Rail split in the middle	Half the board has no power	Bridge the gap
Leg not pushed in fully	Works sometimes	Push firmly; trim long legs

Examples

Example: an LED and resistor, placed right

• Resistor: one leg in the + rail, the other in row 10, column a.
• LED long leg: row 10, column c (same row as the resistor, so they connect).
• LED short leg: row 11, column c.
• Jumper: row 11 to the − rail.

Each connection happens because two legs share a 5-hole row, never because they “touch”.

Example: debugging by rows

A circuit doesn’t work. Trace it row by row: + rail → resistor → row 10 → LED → row 11 → jumper → − rail. If any step jumps to a row that isn’t connected, that’s the break.

Practice

Try it

Practise placing parts on a virtual breadboard:

1. Press Start simulator, then the blue + button, and add a Half Breadboard, an LED and a Resistor.
2. Drag the LED and resistor onto the breadboard so their legs are in different rows. Using the diagram above, work out which holes now connect to each leg.
3. Click a pin of the Arduino’s 5V, then a hole on the + rail, to draw a wire. Do the same for GND to the − rail.

We’ll make it light up properly in the next lesson.

Virtual breadboard and ArduinoOpen full screen ↗

Start simulator

Runs on Wokwi, free, no account needed.

Rails firstEasy

In the virtual breadboard, wire the Arduino’s 5V to the + rail and GND to the − rail.

Find the shortMedium

A friend placed both legs of a resistor in row 15 on the same side. What happens, and how do you fix it? Both legs are connected together, so the resistor is shorted out and does nothing. Rotate it so the legs sit in two different rows.

Across the gapHard

Why do chips and push buttons sit across the centre gap? Each pin then lands in its own row. Without the gap, pins on opposite sides of the chip would be connected to each other through the same row.

Quick check

1. Which holes are connected together in the middle section?

Each long columnEach row of 5 holes on one side of the gapAll of themNone of them

2. What are the long + and − lines along the edges for?

DecorationSupplying power and ground along the boardHolding chipsMeasuring voltage

3. You put both legs of a resistor in the same 5-hole row. What happens?

It works normallyIt is shorted out and does nothing usefulIt doubles its resistanceIt explodes

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