Circuit board

The components of an electronic circuit are nearly always assembled on a rectangle of circuit board. This is made from insulating material and has conducting copper tracks on its underside to make the connections between components. In the circuits described in this book, we use components that have wire terminals. The wires are pushed through holes in the board and soldered to the tracks on the other side of the board. Another type of component is the surface mount device (SMD) which has terminal pads that are soldered to tracks on the same side of the board. No holes are required. SMDs are very small and difficult to handle, so we do not use this type in the book. Take care not to ask for the SMD type by mistake when buying components.

In this book we build the circuits on stripboard, which has parallel copper strips, ten to the inch, perforated with holes, also ten to the inch. It is bought ready to use and allows the layout to be varied to suit the sizes of the components, and altered later if any changes are needed. It is more economical to purchase the board as a large sheet (about 300 mm long by 100 mm wide) and cut it into smaller pieces with a junior hacksaw.

The copper strip side of standard stripboard.

One of many more elaborate circuit boards, intended for integrated circuits (which include PICs).

Components are connected by soldering them to the strips and also by soldering connecting wires at right-angles across the board to connect some of the strips. This is known as the Manhattan layout. The drawing shows how it works.

A typical stripboard layout, with strips running east-west and connecting wires running north-south.

While thinking about circuit board layout now is a good chance to say a few things about the layout diagrams in this book. The first point is that they are drawn as if the board is transparent. They show the components, which are on the top side, and the strips, which are below. They also show the circular cuts in the strips, which are not actually visible on the component side of the board. The two larger, clear circles are holes drilled in the board for mounting it on a pair of bolts.

The large circular dots are the places where leads are soldered to the strips beneath the board, and these too are not visible from the component side.

The components in this drawing comprise a 2-way screw terminal (top left), two 4-way header plugs (centre left and right) and four transistors.

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