Data Sheet

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16. The Bi-directional LED
Build the circuit above, press the switch (62) and you will see the bi-
directional LED (71) turn on red. Now install the bi-directional LED (71)
in the reverse direction and when you press the switch (62) the bi-
directional LED (71) will turn on blue. Bi-directional LEDs actually have
two diodes in them in opposite directions so current can ow in both
directions. But current is only owing through one diode at a time, which
determines which color LED lights.
17. Bi-directional LED Sensor
Replace the switch (62) with the press switch (61), press the press
switch (61) and the bi-directional LED (71) will ash on and off. If you hold
the press switch (61), the bi-directional LED (71) will turn on red. Install
the bi-directional LED (71) in the reverse direction, then hold the press
switch (61) and you will see the bi-directional LED (71) turn on Blue. Bi-
directional LEDs can be used as sensors that indicate which direction
current is owing.
18. Simulating a Short Circuit
Build the circuit above making sure the colorful LED (72) is in the correct
direction. Press the switch (62) to turn on both the colorful LED (72) and
the lamp (76). Press the press switch (61) and the colorful LED (72)
will turn OFF but the lamp (76) will get brighter. By pressing the press
switch (61) you are simulating a short circuit that results in a much lower
resistance path for current to ow (i.e. through the press switch (61)
rather than through the colorful LED (72)) which causes the colorful LED
(72) to stop working. Typically, short circuits occur due to unintended
contacts of components that result in accidental diversion of the current.
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