Elenco Electronics SC3DMEG Instruction Manual page 79

Project 134
Build the circuit and close (turn on) the slide switch (S1). The LEDs (D9 &
D11) light.
Current flows from the batteries through the LEDs and back to the battery
through the switch. The closed (on) switch completes the circuit. In
electronics this is called a closed circuit. When the switch is open (off), the
current can no longer flow back to the battery, so the LEDs turn off. In
electronics this is called an open circuit. Engineers refer to switches being
open or closed because the switch symbol resembles an architect's
symbol for a door.
Project 136
LEDs in Series
Place the parts on the base grid, then assemble the parts on the three 90 degree
vertical snap wires (V1). The LEDs are in parallel so when you turn the switch
on, all should light.
Change the circuit by switching the LEDs around or add sound by replacing the
color2 LED (D12) with the melody IC (U32).
Project 135
When you close (turn on) the slide switch (S1), both LEDs (D9 & D11) turn
on. Current flows from the batteries through the switch back to the battery
through the LEDs. Remove the red LED (D11) and notice that the blue LED
(D9) does not change in brightness. In a parallel circuit each part has its
own path to the battery so removing one LED does not affect the other one.
The voltage is the same across the LEDs, but not the current.
LEDs in Parallel
Cross Over
Project 137
Cross Over Tree
Use the preceding circuit, but
place the fiber optic festive tree
on the color2 LED (D12) using
the mounting base.
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