Operation Manual

yours didn’t, buy a separate stand-and-sponge set.
• Side Cutters—Through-hole components have long legs, which are left sticking out after you’ve soldered them in place.
Side cutters allow you to cleanly and quickly trim these excess legs without damaging the solder joint.
• Tweezers—Electronics components can be small and fiddly, and a good pair of tweezers is invaluable. If you’re thinking of
using surface-mount components, instead of the easier-to-solder through-hole components, tweezers are an absolute
necessity—without tweezers, you’ll burn your fingers if you try to hold the component and solder it at the same time!
• Work Stand—Commonly referred to as helping hands, these are weighted stands with clamps or clips that hold the item to
be soldered in place. Some work stands include an integrated magnifying glass for delicate work, while the most expensive
work stands add a light to help illuminate the work area.
• Multimeter—Multimeters are test meters that have multiple functions including voltage, resistance and capacitance
measurement, along with continuity testing for finding breaks in circuits. Although a multimeter is not an absolute necessity, it
can be extremely useful for diagnosing issues with circuits. Professional multimeter units can be quite expensive, but a simple
model is fairly inexpensive and is a sound investment for anyone getting started in electronics.
• Desoldering Wick—Mistakes happen, but they don’t have to be permanent. A desoldering wick is a braided metal tape
that can be placed over a solder joint and heated, pulling the solder away from the component and into the wick. With
practice, it’s possible to use a desoldering wick to salvage components from discarded electronic equipment—a handy way
to gather common components cheaply.
Reading Resistor Colour Codes
Most electronic components are clearly labelled. For example, capacitors will have their capacitance, measured in farads, printed
directly on them, while crystals will have their frequency likewise marked.
The major exception is a resistor, which typically has no writing on its surface. Instead, the resistance value in ohms is calculated
from the colour bands that adorn the resistor’s surface. Learning to decode these bands is an important skill for a hardware
hacker to learn, because once a resister is removed from its packaging, the only way to figure out its value is to use a multimeter,
which is an awkward and slow measuring tool for this particular job.
Thankfully, the resistor colour codes follow a logical pattern. Figure 12-1 shows a typical four-band resistor. A high-resolution
colour version of this diagram is available on the Raspberry Pi User Guide website at
http://www.wiley.com/go/raspberrypiuserguide. The first two bands are assigned a colour that equates to a resistance
value in ohms. The third band is the multiplier, by which the first two numbers are multiplied to arrive at the actual resistance
value. The final band indicates the tolerance of the resistor, or how accurate it is. A resistor with a lower tolerance will be closer
to its marked value than a resistor with a higher tolerance, but you’ll pay more for the component.
Figure 12-1: A four-band resistor and the decoding table for its colour code