Elenco Upgrade Kit SC500 to SC750 - Manual (Page 30)

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Project #559
OBJECTIVE: To use the sun to make alarm sounds.
Solar Alarm
Set the meter (M2) to the LOW (or 10mA) scale. With the slide switch
(S1) off, make sure you have a bright light on the solar cell (B2) so the
meter reads 10 or higher. Now turn on the slide switch and listen to
the sound.
The meter is used to measure if the solar cell can supply enough
current to operate the alarm IC (U2). Some types of light are better
than others, but bright sunlight is best.
Project #560
OBJECTIVE: To use the sun to make alarm sounds.
Better Solar Alarm
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 listen to
the sound.
This circuit uses the transformer (T1) to boost the current to the
speaker (SP), allowing it to operate with less power from the solar cell.
Compare how much light it needs to project #559, which doesn’t have
a transformer.
You can change the sound from the alarm IC (U2) using the same
variations listed in projects #61-65.