Data Sheet

Project 73 Super Buzzer
Build the circuit as shown, and turn on the slide
switch (S1); you may hear a buzzing sound as the
relay (S3) turns on and off rapidly. Adjust the
sound by pushing the press switch (S3), raising
and lowering the iron core rod in the electromag-
net (M3), or by placing the magnet near the reed
switch (S9) to activate it and the white LED (D6);
try combinations of these and see how the sound
changes.
Project 72 Alternating Voltage
Build the circuit as shown (leave the fan off the motor), and turn
on the slide switch (S1); you hear a buzzing sound as the relay
(S3) turns on and off rapidly. Set the switcher (S6) to the top or
bottom position to turn on the motor (M1) and white LED (D6).
The electricity supplied to your home and school by your local
electric company is not a constant voltage like that from a bat-
tery. It averages about 120V but is constantly changing, due
to the design of the generators that produce it. This is not a
problem, since all equipment that uses it accounts for this
change. Its frequency is 60 Hz.
An electrical current that is changing is called an alternating
current, or AC. Because of this, the power from the electric
company is also called AC power. An electrical signal that is
constant and unchanging is called a direct current, or DC.
The power from a battery is also called DC power.
In project 85 and others the LED only works in one of the switcher
(S6) settings, but in this circuit it works in either the top or bottom
S6 setting. Why?
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