Hardware Reference
In-Depth Information
Figure 3-4.
On an LED, the longer lead (on the left side) is the anode. The
shorter lead (on the right side) is the cathode. The anode connects to posi-
tive voltage and the cathode connects to ground.
4. Insert the LED's cathode (the shorter wire) into the same row of the
breadboard that's connected to ground. The anode (the longer wire) can
be inserted into an unused row on the breadboard.
5. To complete the circuit, you need to insert a
resistor
as well,
in series
with
the LED. The value of the resistor depends on the characteristics of LED
you are using and how much electrical current the Galileo provides
through the digital pins (10 milliamperes). For a typical red LED, use a
330-ohm resistor, which has bands colored orange, orange, brown, and
then gold or silver. See appendix
Appendix C
on determining resistor
values based on their color bands.
This
handy resistor calculator for LEDs
can help you determine
the right resistor to use with your LED. The source voltage will
be 5 volts, the diode forward voltage depends on your LED
(typically 2 volts for a red LED), and the forward current should
be set to 10 mA to match the current that Galileo will provide.
Your resistor value doesn't need to be spot on, but get it as
close as possible.
