Elenco LIGHT - Manual (Page 43)

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Project 61 Brightness Control
Project 62 Resistors Project 63
Resistors & LEDs
Use the circuits from projects 61 and 62, but
replace the white LED (D6) with the red LED
(D1) or color LED (D8). Vary the adjustable
resistor lever and change the yellow resistors to
see how the light varies with each LED.
Use the circuit built in project 61, but replace the 3-snap with one
of the yellow resistors in this set (R1, R3, or R5). Observe how
each changes the LED brightness at different settings for the
adjustable resistor.
Build the circuit and turn on the slide switch (S1). Move the lever on the
adjustable resistor (RV) to vary the brightness of the light from the white
LED (D6). If desired, you may place any of the LED attachments (tower,
egg, or fiber optic tree) on the LED.
Resistors are used to control or limit the flow of electricity in a circuit.
Higher resistor values reduce the flow of electricity in a circuit.
In this circuit, the adjustable resistor is used to adjust the LED brightness,
to limit the current so the batteries last longer, and to protect the LED
from being damaged by the batteries.
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.
The adjustable resistor can be set for as low as 200 Ω , or as high as
50,000 Ω (50k Ω ).
The R1 resistor (100
Ω
) will have
little effect, since it will be
dominated by the adjustable
resistor. Resistor R5 (100k
Ω ) is a
high resistance, which greatly
restricts the flow of electricity, so
the LED will be very dim or off.
Resistor R3 (5.1k
Ω ) will be in
between those.