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Project #280
Turn the slide switch (S1) on and set the adjustable resistor (RV)
control so the motor just starts spinning. Slowly cover the
photosensitive resistor (RP) and the motor spins faster. By placing
more light over the photosensitive resistor, the motor slows.
Electric Fan Stopped by Light
Project #281
OBJECTIVE: To control large currents with a small
Place the fan on the motor. Turn the slide switch (S1) on and the motor
spins. The transistors are like two switches connected in series. A
small current turns on the NPN transistor, which turns on the PNP
transistor. The large current used to spin the motor now flows through
the PNP. The combination allows a small current to control a much
larger one.
Press the press switch (S2) and the lamp lights and slows the motor.
When the lamp lights, the voltage across the motor decreases and
slows it down.
Motor & Lamp
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