Datasheet

Shield, Lights, Servo Motors • Chapter 2
Robotics with the BOE Shield-Bot • 47
Activity 2: Build and Test LED Indicator Lights
Indicator lights give people a way to see a representation of what’s going on inside a device,
or patterns of communication between two devices. Next, you will build indicator lights to
display the communication signals that the Arduino will send to the servos. If you haven’t
ever built a circuit before, don’t worry, this activity shows you how.
Introducing the Resistor
A resistor is a component that resists the flow of electricity. This flow of electricity is
called current. Each resistor has a value that tells how strongly it resists current flow. This
resistance value is called the ohm. The sign for the ohm is the Greek letter omega: Ω. (Later
on you will see the symbol kΩ, meaning kilo-ohm, which is one thousand ohms.)
This resistor has two wires (called leads and pronounced “leeds”), one coming out of each
end. The ceramic case between the two leads is the part that resists current flow. Most
circuit diagrams use the jagged line symbol with a number label to indicate a resistor of a
certain value, a 470 Ω resistor in this case. This is called a schematic symbol. The part
drawing on the right is used in some beginner-level texts to help you identify the resistors in
your kit, and where to place them when you build circuits.
The resistors in your parts kit have colored stripes that indicate what their resistance values
are. There is a different color combination for each resistance value. For example, the color
code for the 470 Ω resistor is yellow-violet-brown.
There may be a fourth stripe that indicates the resistor’s tolerance. tolerance is measured in
percent, and it tells how far off the part’s true resistance might be from the labeled
resistance. The fourth stripe could be gold (5%), silver (10%) or no stripe (20%). For the
activities in this book, a resistor’s tolerance does not matter, but its value does.
470 Ω
Yellow
Vio
let
Brown
Gold
Silver
or
Blank