Elenco Projects 512-692 - Manual (Page 57)

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Project #625
OBJECTIVE: To construct an LED flasher.
LED Flasher
Set the adjustable resistor (RV) to the top position and then turn on the
slide switch (S1). The LED’s (D1 & D2) flash at a rate of once per
second. As you adjust RV’s knob down, the LED’s flash faster. When
RV is at the bottom, the LED’s turn off.
Project #626
OBJECTIVE: To construct an LED flasher with sound.
LED Flasher with Sound
You can modify project #625 by adding a transformer (T1) to drive a speaker
(SP). Set the adjustable resistor (RV) to the top position and turn on the slide
switch (S1). The speaker sounds as the LED (D2) flashes several times per
second. Increase the rate by moving RV’s knob down.
OBJECTIVE: To construct an LED flasher with sound.
LED Flasher with Sound (II)
Project #627
Modify the frequency by replacing the 0.1 μ F capacitor (C2) with the 10 μ F
capacitor (C3, “+” side on the right).