Elenco Upgrade Kit SC500 to SC750 - Manual (Page 23)

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Cover the solar cell (B2) and turn on the slide switch (S1), there should
be little or no light from the LED’s (results depend on your batteries).
Shine a bright light on the solar cell and the red (D1) and green (D2)
LED’s should be bright, along with one segment of the 7-segment
display (D7).
This circuit shows how it takes a lot of voltage to turn on a bunch of
diodes connected in a series. Since the transistors (Q1 & Q2) are
used as diodes here, there are six diodes total (D1, D2, D3, D7, Q1,
and Q2). The voltage from the batteries (B1) alone is not enough to
turn them all on at the same time, but the extra voltage produced by
the solar cell is enough to make them bright.
Now push the press switch (S2) and D7 will display “0.”, but it will be
dim unless the light on the solar cell is very bright. With S2 off, all the
current through D7 goes through segment B and makes it bright. With
S2 on, the current through D7 divides evenly between several
segments.
Project #542
OBJECTIVE: To learn more about diodes.
Diode Wonderland
Project #543
OBJECTIVE: To show the difference between the low and high
current meter ranges.
Meter Ranges
Use the LOW (or 10mA) setting on the meter (M2), turn off the slide
switch (S1), and unscrew the 2.5V bulb (L1). The meter should
measure about 2, since the 100K
Ω resistor (R5) keeps the current low.
Results will vary depending on how good your batteries are.
Screw in the 2.5V bulb to add the 10K Ω resistor (R4) to the circuit, now
the meter reading will be about 10.
Change the meter to the high-current HIGH (or 1A) setting. Now turn
on the slide switch to add the 100
Ω resistor to the circuit. The meter
should read just above zero.
Now press the switch (S2) to add the speaker (SP) to the circuit. The
meter reading will be about 5, since the speaker has only about 8
Ω
resistance.