Data Sheet

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126. The Colorful LED
Build the circuit shown and turn on the switch (62). Whenever light
shines on the photoresistor (68), the colorful LED (72) will be off. Cover
the photoresistor (68) with your nger and the colorful LED (72) will turn
on and light the ber tree (40). The colorful LED (72) is made of three
LEDs (one Red, one Green, and one Blue) connected to a tiny Integrated
Circuit (IC) that varies the percentage of time each LED is “ON”. For
instance, the colorful LED (72) will look red if the red LED inside is ON
100% of the time and the green and blue LEDs are OFF 100% of the
time. But if both red and green are on 100% of the time and the blue
LED is OFF 100% of the time, then the colorful LED (72) will look yellow.
Similarly, red & blue ON will look magenta (purple) and green & blue ON
will look cyan (light blue). In between colors can be formed by adjusting
the percentage of time each LED is on between 0-100%.
127. Angular Light Intensity
Build the circuit shown on the left and turn on the switch (62). Whenever
light shines on the photoresistor (68), the bi-directional LED (71) will be
off. Cover the photoresistor (68) with your nger and the bi-directional
LED (71) will turn on red. While it may appear that the bi-directional
LED (71) is brighter than the heart LED (69), this is because LEDs have
angular light intensity proles such that a majority of the light emits
straight out of the top of the LED. If you look from the side at the bi-
directional LED (71), you will see it looks very dim, just like looking at the
side of the heart LED (69).
128. 4-Band Resistor
Reverse the direction of the bi-directional LED (71) in project #127 and
turn on the switch (62). Whenever light shines on the photoresistor
(68), the bi-directional LED (71) will be off. Cover the photoresistor
(68) with your nger and the bi-directional LED (71) will turn on blue.
Although the resistor values in your Circuit Blox™ 395 set are labeled
(e.g. 100kW in this project), physical resistors are often labeled using a
color code. Below is a picture of a 4-band resistor. The rst three bands
on the left dene the resistance value of the resistor, while the last band
on the right denes the tolerance of the resistor.
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