Data Sheet

-33-
34. Red and Blue Light Wavelength
Build the circuit shown on the left, press the switch (62) and the heart
LED (69) will light and the bi-directional LED (71) will be red. Reverse the
direction of the bi-directional LED (71) and it will be blue. LEDs produce
different colors by transmitting light waves with different wavelengths.
Light waves cycle up and down and a wavelength is the distance between
successive crests of the wave. Red light has a wavelength of around
665 nanometers, while blue light has a wavelength of around 470
nanometers. A nanometer is 1 billionth of a meter.
35. ON-OFF Switch
Build the circuit shown on the left , press the switch (62), and you will see
the heart LED (69) and the bi-directional LED (71) turn on at the same
time. The switch (62) is commonly called an on/off switch since it just
turns the circuit on or off from one location. For that reason, it’s also
referred to as single location switch. Inside an on/off switch, there’s a
spring-loaded gate. When you change the switch to ON, that gate snaps
closed. It closes the circuit and lets current ow through the switch.
When you change it to OFF, the gate snaps open. It opens the circuit and
interrupts the ow of current.
36. Details of Morse Code
Replace the switch (62) with the press switch (61). Press and release the
press switch (61) and you will see the heart LED (69) and bi-directional
LED (71) ash On and Off. As discussed in project #32, this circuit could
be used to send Morse code sequences. The International Morse Code
is shown below where a dot represents a quick push of the press switch
(61) and a dash represents holding the press switch (61) for a second.
Try sending letters or a code to a friend and see if they can decode it by
looking at the LEDs.
Morse
Code