Elenco Upgrade Kit SC100 to SC750 - Manual (Page 28)

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Project #168
NPN Light Control
OBJECTIVE: To compare
transistor circuits.
Project #169
NPN Dark Control
Turn on the slide switch (S1),
the brightness of the LED (D2)
depends on how much light
shines on the photoresistor
(RP). The resistance drops as
more light shines, allowing more
current to the NPN (Q2).
OBJECTIVE: To compare
transistor circuits.
Turn on the slide switch (S1),
the brightness of the LED (D2)
depends on how LITTLE light
shines on the photoresistor
(RP). The resistance drops as
more light shines, diverting
current away from the NPN
(Q2).
Project #170
PNP Light Control
OBJECTIVE: To compare
transistor circuits.
Project #171
PNP Dark Control
Turn on the slide switch (S1),
the brightness of the LED (D1)
depends on how much light
shines on the photoresistor
(RP). The resistance drops as
more light shines, allowing more
current through the PNP (Q1).
This is similar to the NPN (Q2)
circuit above.
OBJECTIVE: To compare
transistor circuits.
Turn on the slide switch (S1),
the brightness of the LED (D1)
depends on how LITTLE light
shines on the photoresistor
(RP). The resistance drops as
more light shines, so more
current gets to the 100k
Ω
resistor (R5) from the
photoresistor path and less from
the PNP-diode path. This is
similar to the NPN circuit above.
Visit www.snapcircuits.net or page 74 to learn about Snap Circuits ® upgrade kits, which have more parts and circuits.