Manual Part 2

56
TRANSISTORS
The NPN transistor (Q2) is a component that
uses a small electric current to control a large
current, and are used in switching, amplier, and
buffering applications. Transistors are easy to
miniaturize, and are the main building blocks of
integrated circuits including the microprocessor
and memory circuits in computers.
NPN Transistor (Q2)
The phototransistor (Q4) is a transistor that
uses light to control electric current.
Phototransistor (Q4)
CAPACITOR
The 470µF capacitors (C5) can store
electrical pressure (voltage) for periods of
time. This storage ability allows them to block
stable voltage signals and pass changing
ones. Capacitors are used for ltering and
delay circuits.
LEDs SOUND MODULE
The melody IC (U32) contains a specialized
sound-generation integrated circuit (IC),
a small speaker, and a few supporting
components. The IC has a recording of the
melody, which it makes into an electrical
signal for the speaker. The speaker converts
the signal into mechanical vibrations. The
vibrations create variations in air pressure,
which travel across the room. You “hear”
sound when your ears feel these air pressure
variations.
LAMP
A light bulb, such as in the 4.5V lamp (L4),
contains a special thin high-resistance wire.
When a lot of electricity ows through, this wire
gets so hot it glows bright. Voltages above the
bulb’s rating can burn out the wire.
LEDs
(D6 & D8)
The white and color LEDs (D6 & D8) are
light emitting diodes, and may be thought of as
a special one-way light bulbs. In the “forward”
direction, (indicated by the “arrow” in the
symbol) electricity ows if the voltage exceeds
a turn-on threshold brightness then increases.
The color LED contains red, green, and blue
LEDs, with a micro-circuit controlling then.
A high current will burn out an LED, so the
current must be limited by other components
in the circuit (Snap Circuits
®
LEDs have
internal resistors added, to protect them in
case you make wiring mistakes). LEDs block
electricity in the “reverse” direction.
Capacitor (C5)
4.5V Lamp (L4)
ABOUT YOUR SNAP CIRCUITS
®
PARTS