Elenco Snap Circuits® Deluxe Sound & Light Combo - Manual (Page 143)

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Build the circuit and turn the slide switch (S1). Push the press switch
(S2) and play keys on the keyboard (U26). Play fast, because this
keyboard will only work for a few seconds! Push S2 again to restart the
keyboard and its timer.
Turn on the slide switch (S1). Set the lever on
the adjustable resistor (RV) all the way to the
left. The color LED (D8) should be on, but may
be mostly red. Slowly move the lever on RV to
the right until the LED is completely off. Notice
that the red color stays on the longest.
Now push the press switch (S2) and adjust RV
again, watching the LED colors. Blue and green
color may also appear now, but may go dim
before red does.
Now move S1 from the points marked C & D to
the points marked A & B. Move RV’s lever
around again, watching the LED colors and
brightness. Try pushing S2 again, but it won’t
make as much difference now.
Project 332 Play Fast
Project 333 Red First
The voltage needed to turn on an LED
depends on the light color. Red needs the
least voltage, and blue needs the most.
With S1 at points C & D and S2 off, the
voltage to the color LED is lowest, and may
barely be enough to turn on the red color.
Pressing S2 bypasses the NPN transistor
(Q2), and boosts the LED voltage a little.
Shifting S1 to points A & B increases the
circuit voltage from 3V to 6V, making the
LED work for a greater part of RV’s range.
SCC-350_Manual_Part_C.qxp 7/25/14 2:11 PM Page 31