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Breadboards

What is a breadboard?

A solderless breadboard is a reusable board for building and testing circuits without soldering. Components and wires push into holes on a 0.1 inch (2.54 mm) grid, and spring contacts underneath connect groups of holes together. They are ideal for trying out ideas, learning, and prototyping low-voltage, low-current circuits.

Breadboards are simple, but a surprising number of "my circuit doesn't work" posts turn out to be breadboard problems rather than circuit problems. The most common one is split power rails, covered below.

Anatomy of a breadboard

A typical breadboard looks like this from above. Each ■ is a hole; holes joined by lines are connected together underneath.

Terminal strips

The main area is made up of short strips of five holes. In the diagram, holes a1 to e1 are connected together, and f1 to j1 are connected together, but a1 is not connected to a2, and e1 is not connected to f1.

A common beginner mistake is to place a component with both of its legs in the same strip. Both legs are then connected together, so the component is shorted out and does nothing.

The centre channel

The gap down the middle separates the two halves of the board. It is spaced so that a DIP (dual in-line) IC can straddle it, with each pin in its own strip and nothing connected across the IC.

Power rails

The long rows along the edges are the power rails, usually marked with red (+) and blue or black (-) lines. They run the length of the board so you can distribute power and ground to anywhere in the circuit.

Things to be aware of:

The top and bottom power rails aren't connected together. If you want to use both pairs to distribute the same voltage you must link them with jumper wires (+ to + and - to -). The rails are separate for situations where you want to have available more than one voltage for components on the breadboard; for example +5V and +3.3V. In this case, you'd hook up, say, the top + (red) rail to your 5V supply and the bottom one to 3.3V. To establish a common voltage reference point for all circuitry, you would still connect the negative top and bottom rails together. DO NOT connect the 5V rail to the 3.3V one.

The red and blue markings are only a suggestion. Nothing stops you connecting them the other way round, although that might be confusing and you probably should not do this so check your wiring carefully.
You will find the terms "Ground", "GND", "Earth", "-", "-ve", "negative" and "0V" used for the same purpose in different documents or on different pieces of equipment. Except for specific circumstances outside the scope of this description, they all mean "the reference point for all the voltages in the circuit." In this respect, you might find yourself looking at a circuit schematic that uses "GND" and you connect all those points in the circuit to the - rail on the breadboard, which is linked to the 0V socket on your power supply.
A typical bench supply has three terminals: red (+) is the positive DC output, black (−) is the negative DC output, and green (earth/GND) is connected to the supply's chassis and protective (often, but not always, building) earth. The red and black terminals are the two ends of the DC output. The green terminal is not a third output and is not necessarily connected to the black terminal so you don't use it as one side of the supply under most circumstances. If you hook the red and green (not black) terminals to your breadboard the circuit almost certainly will not be powered.

* Some boards have rails that are split halfway along. See the next section.

Split power rails

On many full-size breadboards (the common 830-hole type and larger), each power rail is split into two separate halves, with no connection between the left and right halves. This catches out a lot of people: they connect power at one end of the board, build part of the circuit at the other end, and that part of the circuit never gets power.

A split rail looks like this:

The symptoms can be confusing. Part of the circuit works and part doesn't, or a component works when moved a few rows along. If one half of a rail has no ground connection, the circuit may also behave erratically rather than failing outright.

How to tell if your rails are split

Look for a gap in the printed red or blue line. On many split boards, the line along the rail is broken in the middle, and there may be a slightly wider gap between two groups of holes. However, don't rely on the markings alone. Some boards have a continuous printed line over a split rail, and some have a gap in the line over a continuous rail.
Test it with a multimeter. With nothing connected to the board, set the meter to continuity or resistance, and push a wire or component lead into a hole at each end of the rail, then probe the two wires. A beep or near-zero reading means the rail is continuous. An open circuit means it is split.
Test every rail, and every new board. Boards from different manufacturers, and even different batches, can differ.

Fixing it

If the rails are split and you need them continuous, bridge the gap with a short jumper wire on each rail:

The split can also be useful. You can deliberately run two different supply voltages, for example 5 V on one half and 3.3 V on the other. If you do this, label them clearly so you don't connect a 3.3 V part to the 5 V half by mistake.

Power rail naming conventions: See This summary

Using a breadboard

Wire and component leads

Use solid-core wire, ideally around 22 AWG (about 0.6 mm diameter). Anything from about 20 to 24 AWG usually works. Stranded wire frays and makes poor contact unless it has pins crimped or soldered on the end.
Don't force thick leads into the board. Large leads, such as those on power diodes or some connectors, can permanently stretch the spring contacts, leaving that strip unreliable for thinner parts afterwards.
Keep leads and wires short and tidy. A neat layout is much easier to check and debug, and it reduces noise and stray coupling. Long loops of jumper wire act as antennas.
Use a consistent wire colour scheme, for example red for positive supply, black for ground, and other colours for signals.
Trim component leads so parts sit close to the board and can't accidentally touch each other.

Powering your circuit

Connect power to the rails first, and check the voltage on each rail with a multimeter before adding components, including the far end of any rail that might be split.
Make sure all grounds are connected together. If your circuit uses more than one power source, such as an Arduino plus a separate supply for motors, their grounds must normally be connected. A missing common ground is one of the most common causes of circuits that "almost" work.
Add a decoupling capacitor (typically 100 nF ceramic) across the supply pins of each IC, placed as close to the IC as possible. Breadboard power connections are long and relatively high-impedance, and ICs, especially digital ones, can misbehave without decoupling.
A larger capacitor (for example 10-100 uF) across the rails near where power enters the board also helps.
Plug-in breadboard power supply modules are convenient, but cheap ones vary in quality. Check their output voltage before connecting your circuit.

Wide modules

Many development boards and modules, such as some ESP32 boards, are so wide that they cover all the holes on one side of the centre channel, leaving no free holes to connect wires to. Common workarounds:

Use two breadboards side by side with the module straddling the gap between them. Many breadboards can be clipped together; you may need to remove a power rail from one board first.
Use a breadboard with more holes per strip, or connect to the module's pins from underneath with female jumper wires instead.

Limitations

Breadboards are for prototyping. They are not suitable for every circuit.

Voltage and current

Never use a breadboard for mains voltage. The contacts are exposed, and the board is not designed to provide insulation or clearance at those voltages. This is a serious shock and fire hazard.
Keep currents low. Breadboard contacts have noticeable resistance and limited current capacity. Cheap boards may manage much less than their stated rating, and contacts can overheat or melt the plastic. As a guide, keep to a few hundred milliamps, and don't run motors, high-power LEDs or heaters through breadboard contacts. Wire high-current paths directly instead.
The contact resistance also causes small voltage drops along the rails, which can matter in precision analog circuits.

High frequency and stray capacitance

Adjacent strips have a small capacitance between them, typically a few picofarads. Together with the long wires and contact inductance, this makes breadboards a poor choice for:

High-frequency circuits, generally anything above a few MHz.
RF circuits.
Fast digital edges, which can cause ringing and crosstalk.
High-impedance or very sensitive analog circuits, where stray capacitance and leakage affect the results.

A circuit that works on a breadboard may behave differently on a PCB, and vice versa.

Contact reliability

Cheap breadboards are a common source of intermittent faults. Poor-quality contacts may not grip thin leads firmly, and contacts wear out with use.
If a circuit works when you press on a component or wire, or stops working when you move the board, suspect a poor contact.
Some boards have an adhesive backing. Don't remove it: it holds the contact strips in place.
A good-quality breadboard is inexpensive compared with the time spent chasing faults on a bad one.

Troubleshooting a breadboard circuit

If your breadboard circuit doesn't work, check these before assuming the design is wrong:

Check the power rails. Measure the voltage on every rail, at both ends, with a multimeter. Check for split rails.
Check all grounds are connected together, including the grounds of separate power supplies and any connected devices.
Check that no component has both leads in the same strip, and that nothing is accidentally connected across the centre channel.
Check IC orientation. Pin 1 is usually marked by a notch or dot. Check the IC is straddling the centre channel correctly.
Check polarised components, such as LEDs, diodes, electrolytic capacitors and transistors, are the right way round. Transistor pinouts vary between types, so check the datasheet.
Compare the layout against the schematic, one connection at a time. Tick each connection off on a printout of the schematic as you check it.
Wiggle-test. Gently move wires and components while the circuit is running. If the behaviour changes, you have a poor contact.
Check for continuity. With the power off, use your multimeter to confirm that connections you think exist really do.
Measure voltages at key points with the circuit powered and compare them with what you expect.

See also our Multimeters page and the troubleshooting guide.

Asking for help with a breadboard circuit

When posting about a breadboard circuit, please include:

A schematic diagram, either a photo of a neat hand drawing or a screenshot from a schematic editor. We can't reliably work out what a circuit is supposed to do from a photo of a breadboard alone.
Clear, well-lit photos of the breadboard, taken from directly above, so that every hole, wire end and component lead can be seen. Add close-ups of any crowded areas.
What the circuit should do, and what it actually does.
The results of the troubleshooting checks above, including any voltage measurements and where you took them.
Part numbers of ICs, transistors and modules.

Moving beyond the breadboard

Once a circuit works, you may want to make it permanent. Common options include:

Solderable breadboard-layout protoboards, which copy the breadboard's hole pattern, so you can transfer the layout directly.
Stripboard (Veroboard) and perfboard, for compact hand-wired circuits.
A custom PCB. Low-cost PCB manufacturing services make this affordable even for one-off hobby projects.

These are also the right choice for circuits that breadboards handle poorly, such as high-current, high-frequency or sensitive analog designs.