Elenco Projects 102-305 - Manual (Page 18)

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Project #126 Sucking Fan
OBJECTIVE: To adjust the speed of a fan.
Project #128 PNP Collector
OBJECTIVE: To
demonstrate adjusting the
gain of a transistor circuit.
OBJECTIVE: To build a fan that
won’t come off.
Modify the circuit from project #126 by
reversing the position of the motor
(M1), so the positive (+) side is
towards the PNP (Q1). Turn it on, and
set the adjustable resistor (RV) for the
fan speed you like best. Set it for full
speed and see if the fan flies off - it
won’t! The fan is blowing air upward
now! Try holding a piece of paper just
above the fan to prove this.
Project #127
Blowing Fan
Project #129 PNP Emitter
OBJECTIVE: To compare
transistor circuits.
Compare this circuit to that
in project #128. The
maximum lamp (L2)
brightness is less here
because the lamp
resistance reduces the
emitter-base current, which
contacts the emitter-
collector current (as per
project #128). The point on
the PNP (Q1) that the lamp
is now connected to (grid
point C4) is called the
emitter.
Build the circuit, and be sure to orient the motor (M1)
with the positive (+) side down as shown. Turn it on,
and set the adjustable resistor (RV) for the fan speed
you like best. If you set the speed too fast then the fan
may fly off the motor. Due to the shape of the fan
blades and the direction the motor spins, air is sucked
into the fan and towards the motor. Try holding a piece
of paper just above the fan to prove this. If this suction
is strong enough then it can lift the fan blades, just like
in a helicopter.
The fan will not move on most settings of the resistor,
because the resistance is too high to overcome friction
in the motor. If the fan does not move at any resistor
setting, then replace your batteries.
Build the circuit and vary
the lamp (L2) brightness
with the adjustable resistor
(RV), it will be off for most
of the resistor’s range. The
point on the PNP (Q1) that
the lamp is connected to
(point E4 on the base grid)
is called the collector,
hence the name for this
project.
!
WARNING: Moving parts. Do not touch the fan or
motor during operation. Do not lean over the motor.