Elenco Projects 102-305 - Manual (Page 59)

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Project #262
OBJECTIVE: To show how voltage polarity affects a DC motor.
Place the fan onto the motor (M1). Press the press switch (S2). The fan
rotates clockwise. When you connect the positive (+) side of the battery
(B1) to the positive (+) side of the motor, it spins clockwise. Release the
press switch and turn on the slide switch (S1). Now the fan spins the
other way. The positive (+) side of the battery is connected to the negative
(–) side of the motor. The polarity on the motor determines which way it
rotates.
Motor Rotation
OBJECTIVE: To build a circuit that controls how long the fan is on.
Place the fan onto the motor (M1) and set the adjustable resistor (RV) control to the far
right. Turn the slide switch (S1) on and then press the press switch (S2) once. The motor
will spin and then stop. Now set the resistor control to the far left and press the press switch
again. The time the fan spins is much less now.
When the press switch is pressed, the current flows through the circuit and the fan spins.
The 100
μ F capacitor (C4) charges up also. When the press switch is released, the
capacitor discharges and supplies the current to keep the transistors (Q1 & Q2) on. The
transistor acts like a switch connecting the fan to the battery. When the capacitor fully
discharges, the transistors turn off and the motor stops. The adjustable resistor controls
how fast the capacitor discharges. The more resistance, the longer the discharge time.
Project #264
Motor Delay Fan (II)
OBJECTIVE: To change capacitance to affect time.
Use the circuit from project #263. Connect a single snap under the positive (+) side of the
470
μ F capacitor (C5) and then connect it over the top of the 100 μ F capacitor (C4). Turn
the slide switch (S1) on and press the press switch (S2). Notice that the fan spins longer
now. When capacitors are in parallel, the values are added, so now you have 570
μ F. The
time it takes to discharge the capacitors is longer now, so the fan keeps spinning.
Project #263 Motor Delay Fan
!
WARNING: Moving parts. Do not touch the fan or
motor during operation. Do not lean over the motor.
!
WARNING: Moving parts.
Do not touch the fan or motor
during operation. Do not lean
over the motor.