Elenco LIGHT - Manual (Page 64)

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Project 136 Motor Power Project 137
More Motor Power
Use the preceding circuit but replace the red LED
(D1) with the color LED (D8) or the white LED
(D6), see how they compare to the red LED.
!
WARNING: Moving parts. Do not
touch the fan or motor during
operation.
Build the circuit as shown, push the press switch
(S2), and look at the brightness of the red LED
(D1). Try it three ways: with no fan on the motor,
with the glow fan on the motor, and keeping the
motor from spinning with your fingers. When the
motor is spinning, you will hear noise from the
speaker (SP).
The motor needs a lot of electricity to start spinning, but needs less the
faster it is spinning. When kept from spinning by your fingers, the motor
sucks up all the electricity, leaving none to light the red LED. With the fan
on the motor, the LED gets enough electricity to light. When the motor is
spinning without the fan, the LED gets lots of electricity and is bright.
The color and white LEDs
need more electricity to light
than the red LED. The motor
“noise” that you hear on the
speaker can also confuse the
color LED and disrupt its color
pattern.
Project 138 Reflection Detector
Build the circuit as shown and turn on the switch (S1). Place the
mounting base over the phototransistor (Q4). Set the lever on the
adjustable resistor (RV) all the way toward the NPN transistor (Q2).
Move the circuit into a dimly lit room, so that the color LED (D8) is off.
Place a mirror directly over the white LED (D6) and photo-transistor
(Q4), or hold it facing a wall mirror. When enough light from the white
LED reaches the phototransistor, the color LED will turn on, indicating
that a reflection has been detected.
The mounting base is used to block direct light from the white LED to
the phototransistor, and to shield the phototransistor from room light. If
your room is very dark, you may get better results by placing the
mounting base over the white LED instead of the phototransistor.