Chapter 2: Your Boe-Bot’s Servo Motors · Page 47
+
_
LED
Figure 2-3
LED Part Drawing and
Schematic Symbol
Part drawing (above) and
schematic symbol
(below).
The LED part drawings in
later pictures will have a +
next to the anode leg.
When you start building your circuit, make sure to check it against the schematic symbol
and part drawing. If you look closely at the LED’s plastic case in the part drawing, it’s
mostly round, but there is a small flat spot right near one of the leads that that tells you
it’s the cathode. Also note that the LED’s leads are different lengths. In this text, the
anode will be shown with a + sign and the cathode will be shown with a – sign.
Always check the LED’s plastic case. Usually, the longer lead is connected to the LED’s
anode, and the shorter lead is connected to its cathode. But sometimes the leads have been
clipped to the same length, or a manufacturer does not follow this convention. Therefore, it
is best to always look for the flat spot on the case. If you plug an LED in backwards, it will
not hurt it, but it will not light up.
LED Test Circuit Parts
(2) LEDs – Red
(2) Resistors – 470 Ω (yellow-violet-brown)
Always disconnect power to your board before building or modifying circuits! For the
Board of Education Rev C, set the 3-position switch to position-0. For the BASIC Stamp
HomeWork Board, disconnect the 9 V battery from the battery clip. Always double-check
your circuit for errors before reconnecting power.
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