User Manual

-5-
About Your Snap Circuits
®
Parts
IN1
(–)
IN2
IN3
OUT
Connections:
IN1, IN2, IN3 - control inputs
(–) - power return to batteries
OUT - output connection
Connect control inputs to (+) power to make five
alarm sounds, see project 169 for an example
of proper connections.
TRANSISTORS
The PNP &NPN transistors (Q1 &Q2) are
components that use a small electric current to
control a large current, and are used in switching,
amplifier, and buffering applications. They are
easy to miniaturize, and are the main building
blocks of integrated circuits including the
microprocessor and memory circuits in
computers.
PNP&NPNTransistors (Q1 & Q2)
ALARMIC
The alarm IC (U2) contains a specialized sound-
generation integrated circuit (IC) and other
supporting components (resistors, capacitors,
and transistors) that are always needed with it.
A schematic for it is available at
www.snapcircuits.net/faq.
Red & Green LEDs (D1 & D2)
Red/Yellow LED (D10)
The red/yellow LED (D10) is like the others but
has red and yellow LEDs connected in opposite
directions.
LEDs
The red & green LEDs (D1 & D2) are light
emitting diodes, and may be thought of as a
special one-way light bulb. In the “forward”
direction, (indicated by the “arrow” in the symbol)
electricity flows if the voltage exceeds a turn-on
threshold (about 1.5V for red and yellow, about
2.0V for green, and about 3.0V for blue;
brightness then increases. A high current will
burn out an LED, so your Snap Circuits
®
LEDs
have internal resistors to protect them. LEDs
block electricity in the “reverse” direction.
Alarm IC (U2)