Manual

Project 52 Dim Color Light
Build the circuit as shown and turn on the slide switch (S1); the color
LED (D8) will be dim. Push the press switch (S2) to make the LED much
brighter.
Replace the color LED (D8) with the white LED (D6).
Project 53
Dim White Light
Resistors are used to control or limit the flow of electricity in a
circuit. In this circuit, the 5.1kW resistor (R3) reduces the LED
brightness, making the batteries last longer.
What is Resistance? Take your hands and rub them together very
fast. Your hands should feel warm. The friction between your hands
converts your effort into heat. Resistance is the electrical friction
between an electric current and the material it is flowing through.
Project 54 Light-Controlled Light
Turn on the slide switch (S1) and vary the amount of light shining on
the phototransistor (Q4). The brighter the light on the phototransistor,
the brighter the color LED (D8) should be. The Q4 attachment is placed
on D8, to make it easier to see if it is dim.
Replace the color LED (D8) with the white LED (D6). Compared
to the color LED, the white LED requires more light on Q4 to
turn on, but gets brighter when there is a lot of light on Q4.
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Project 55
Light-Controlled
White Light
The phototransistor uses
light to control electric
current. As more light shines
on the phototransistor, the
current through it increases,
making the LED brighter.