Hardware Reference
In-Depth Information
There are some fantastic pictures on the Internet of the very first prototypes of
the Raspberry Pi computer that Eben Upton at the Raspberry Pi Foundation built
back in 2006. Most complex circuit boards start off as a prototype like this, and
may go through many revisions and modifications before they end up looking like
the circuit board you have in front of you now. You can see these pictures here:
http://www.raspberrypi.org/raspberry-pi-2006-edition/
Most electronic circuits are soldered together so that the components and the circuit
boards have a very strong and long lasting electrical connection. But while soldered
circuit boards provide a really long-lasting product, they are not very helpful when all
you want to do is experiment with components and design and test circuits, because
you would spend a lot of time de-soldering and re-soldering the components. For this,
engineers will typically use a device called a solderless breadboard .
A breadboard is a reusable device that allows you to create circuits without
needing to solder all the components. Breadboards have a number of holes
into which you push wires or jumper cables and components to create circuits.
The two rows of holes at the top and bottom of the breadboard are for power.
Normally there is a red line, which is used for the positive connection (such as
3.3 volts, sometimes labelled as + or VCC), and a black or blue line, which is used
for the 0 volts (or ground connection, sometimes labelled as - or GND).
Figure 5-4 shows two pictures of a solderless breadboard. On the left is a breadboard
with some components plugged into it to make a circuit, and on the right is a picture
of the insides of the breadboard. If you look closely, you can see the metal strips that
make up the connections. Understanding how a breadboard is wired is very important
because it means that, when you push components into the holes of the breadboard,
you will know how things are going to connect together to make an electrical circuit.
FIGURE.5-4 Left: a breadboard; right, the insides of a breadboard showing its
internal wiring
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