Manual Part 2

38
A
B
C
D
5V
Project 24 | AUDIO FAN SPEED ADJUSTER
Project 25 | DISTANCE LOSS SIMULATOR
Turn on the slide switch (S1). The fan should spin and there should be sound
from the melody IC (U32). If the fan does not spin then push the press switch
(S2) to get the fan started.
This circuit is intended to simulate electrical transmission loss
over long distances. Turn on the slide switch (S1). The color
LED (D8) is bright but the white LED (D6) is not at full brightness.
Set the meter (M6) to the 5V setting and place it across points
A & B to measure the voltage across the color LED, and then
across points C & D to measure the voltage across the white LED.
The speed of the fan varies depending on the
current owing into the melody IC, and the melody
IC current depends on the sound it is making.
The color LED is only separated from the batteries by the slide switch (S1), so
it gets the full battery voltage (pressure) when the switch is on. The white LED
is separated from the batteries by the 5.1kΩ resistor R3 (which represents the
loss of electrical energy when it is transmitted over long distances); this slows
down the current so that the white LED has a noticeably lower voltage across it.
Leaving your charger cord plugged in when there is no phone/device charging wastes electricity.