Breadboard

Uses | Connections | Building Circuit

Also see: Stripboard | PCB

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Uses of Breadboard

A breadboard is used to make up temporary circuits for testing or to try out an idea. No soldering is required so it is easy to change connections and replace components. Parts are not damaged and can be re-used afterwards.

Almost all the Electronics Club website projects started life on a breadboard to check that the circuit worked as intended.

The photograph shows a typical small breadboard which is suitable for beginners building simple circuits with one or two ICs (chips).

Breadboard, photograph © Rapid Electronics

Small Breadboard
Photograph © Rapid Electronics


Connections on Breadboard

Breadboards have many tiny sockets (called 'holes') arranged on a 0.1" grid. The leads of most components can be pushed straight into the holes. ICs are inserted across the central gap with their notch or dot to the left.

Wire links can be made with single-core plastic-coated wire of 0.6mm diameter (the standard size). Stranded wire is not suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.

The diagram shows how the breadboard holes are connected:

Connections on breadboard

The top and bottom rows are linked horizontally all the way across as shown by the red and black lines on the diagram. The power supply is connected to these rows, + at the top and 0V (zero volts) at the bottom.

I suggest using the upper row of the bottom pair for 0V, then you can use the lower row for the negative supply with circuits requiring a dual supply (e.g. +9V, 0V, -9V).

The other holes are linked vertically in blocks of 5 with no link across the centre as shown by the blue lines on the diagram. Notice how there are separate blocks of connections to each pin of ICs.

Larger Breadboards

On larger breadboards there may be a break halfway along the top and bottom power supply rows. It is a good idea to link across the gap before you start to build a circuit, otherwise you may forget and part of your circuit will have no power!


Building a Circuit on Breadboard

Converting a circuit diagram to a breadboard layout is not straightforward because the arrangement of components on breadboard will look quite different from the circuit diagram.

When putting parts on breadboard you must concentrate on their connections, not their positions on the circuit diagram. The IC (chip) is a good starting point so place it in the centre of the breadboard and work round it pin by pin, putting in all the connections and components for each pin in turn.

The best way to explain this is by example, so the process of building this 555 monostable circuit on breadboard is listed step-by-step below. The circuit turns on the LED for about 5 seconds when the 'trigger' button is pressed. The time period is determined by R1 and C1 and you may wish to try changing their values. R1 should be in the range 1kohm to 1Mohm. For further information please see the 555 monostable page.

555 monostable circuit diagram

IC pin numbers

IC pins are numbered anti-clockwise around the IC starting near the notch or dot. The diagram shows the numbering for 8-pin and 14-pin ICs, but the principle is the same for all sizes.

IC pin numbers

Components without suitable leads

Some components such as switches and variable resistors do not have suitable leads of their own so you must solder some on yourself. Use single-core plastic-coated wire of 0.6mm diameter (the standard size). Stranded wire is not suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.

Soldering leads onto switches

Building the example circuit

Monostable Circuit on Breadboard

Begin by carefully insert the 555 IC in the centre of the breadboard with its notch or dot to the left.

Then deal with each pin of the 555:

  1. Connect a wire (black) to 0V.
  2. Connect the 10k resistor to +9V.
    Connect a push switch to 0V (you will need to solder leads onto the switch)
  3. Connect the 470 resistor to an used block of 5 holes, then...
    Connect an LED (any colour) from that block to 0V (short lead to 0V).
  4. Connect a wire (red) to +9V.
  5. Connect the 0.01µF capacitor to 0V.
    You will probably find that its leads are too short to connect directly, so put in a wire link to an unused block of holes and connect to that.
  6. Connect the 100µF capacitor to 0V (+ lead to pin 6).
    Connect a wire (blue) to pin 7.
  7. Connect 47k resistor to +9V.
    Check: there should be a wire already connected to pin 6.
  8. Connect a wire (red) to +9V.

Finally...

If your circuit does not work disconnect (or switch off) the power supply and very carefully re-check every connection against the circuit diagram.


Breadboard Starter Kit

The breadboard kit shown on the right is a good way to get started building circuits on breadboard. As well as a breadboard the kit includes resistors, capacitors, transistors, diodes, LEDs, variable resistors, 555 timer ICs, a 9V battery clip and various colours of wire to make the links.