Elenco Upgrade Kit SC500 to SC750 - Manual (Page 35)

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Project #572
OBJECTIVE: To build a sun-powered oscillator circuit.
Solar Oscillator
Project #574
OBJECTIVE: To learn the principle of an SCR.
Daylight SCR Lamp
Set the meter (M2) to the LOW (or 10mA) scale. Make sure you have
enough light on the solar cell (B2) for the meter to read 3 or higher.
Turn on the slide switch (S1), the lamp (L1) stays off. Push the press
switch (S2) and the SCR (Q3) turns on the lamp and keeps it on. You
must turn off the slide switch to turn off the lamp.
The SCR is a controlled diode. It lets current flow in one direction, and
only after a voltage pulse is applied to its control pin. This circuit has
the control pin connected to the press switch and solar cell, so you
can’t turn it on if the room is dark.
Set the meter (M2) to the LOW (or 10mA) scale. With the slide switch (S1)
off, make sure you have enough light on the solar cell (B2) for the meter
to read 8 or higher. Now turn on the slide switch and adjust the adjustable
resistor (RV).
You will hear a clicking sound like raindrops or a whine, depending upon
how much light there is.
OBJECTIVE: To build a sun-powered oscillator circuit.
Solar Oscillator (II)
Project #573
Use the circuit from project #572 but replace the 10 μ F capacitor (C3)
with the 0.02 μ F or 0.1 μ F capacitors (C1 & C2) to make the sound a
high-pitch whine.