Elenco XP&trade - Manual (Page 6)

-5-
About Your Snap Circuits ® XP TM Parts
The NPN (Q2) transistors 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.
TRANSISTORS
U21 Microcontroller IC:
(+) - power from batteries
(GND) - power return to batteries
S-In - Programming input snap
S-Out /Snap 0 - Serial Output 0
Snap 1 - IN1/OUT1/ADC1
Snap 2 - IN2/OUT2/ADC2
Snap 3 - IN3
Snap 4 -IN4/OUT4/ADC4
Note: There is additional information for
the PICAXE
® 08M integrated circuit at
www.picaxe.co.uk.
The programming cable is used to program and
communicate with the U21 microcontroller.
CABLES
MICROCONTROLLER
Microcontroller outputs cannot control the motor
or speaker directly, an interface transistor must
be used. Microcontroller outputs can control Snap
Circuits
® LEDs directly.
Programming Cable
NPN Transistor (Q2)
The microcontroller IC (U21) includes the
PICAXE
® 08M integrated circuit. This is a mini
computer which can be programmed to perform
different tasks, including monitoring things and
making things happen. The PICAXE
® 08M has a
special programming interface that makes it very
easy to use.
Microcontroller IC (U21)
Notes for using the PICAXE®-08M in other
applications:
Power source:
This should be 4.5V or 5V. Higher voltages
may damage the part.
S-In connection:
The U21 platform has an internal 10K
Ω
resistor between the S-In and GND snaps,
and a 22K
Ω
resistor between the S-In snap
and the microcontroller. These facilitate use of
the programing cable.
Several snaps can be used as either
inputs, outputs, or analog to digital
converters:
as Outputs: Each output can supply or
receive up to 20 mA. This is enough to light an
LED, but an interface transistor must be used
when controlling a motor or speaker.
as Inputs: An input should be above 80% of
the power source voltage to be high, or below
20% of the power source voltage to be low.
as Analog to Digital Converters (ADC): The
ADC range is the power source voltage range.
Circuit resistance should be less than 20K
Ω ,
or false readings may occur.