Elenco Electronics 202 - Manual (Page 32)

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Project #46
OBJECTIVE: To learn about a device that is used to delay
actions in electronics.
Build the circuit and press the press switch (S2). You see that the LED
(D1) turns off slowly after you release the switch.
This delay in turning off the LED is caused by the 470 μF capacitor
(C5). Capacitors can store electricity and are used to delay changes
in voltage. They can block unchanging voltages while passing fast-
changing voltages.
Slow Off Switch
Project #47
Transistor Diodes
OBJECTIVE: To learn about transistors.
Project #48
Four Outputs
OBJECTIVE: To learn about transistors.
Turn on the slide switch (S1), the LED
(D1) and lamp (L2) are bright. This is an
unusual circuit which uses the NPN
transistor (Q2) as two connected diodes
to split the current from the batteries (B1)
into the paths with the LED and lamp. If
the LED does not light, you may have
weak batteries in need of replacement.
Transistors use a small current to control
a large current, and have three
connection points (the small current, the
larger current, and the combined
current). But they are actually
constructed using two diodes that are
connected together. These diodes are
similar to your LED (light emitting diode)
except that they don’t emit light.
This circuit has four different types of
output. Do not place the fan on the motor
(M1). Press the press switch (S2) several
times. The LED (D1) and lamp (L2) are
bright, the motor spins, and the speaker
(SP) makes a static sound. If the LED
does not light, you may have weak
batteries that need replacement.
This is an unusual circuit which uses the
NPN transistor (Q2) as two connected
diodes, to split the current from the
batteries (B1) into the paths with the LED
and lamp.
!
WARNING: Moving parts. Do
not touch the fan or motor during
operation.