Elenco 130-in-1 Electronics Playground - Manual (Page 24)

-137-
This circuit produces short pulses. After you close
the key, the LED display shows 1 for a second and
then turns off, even when you keep pressing the key.
You could create a game with this circuit. Display a
number or a letter on the LED display and then have
the players tell you what number it is. You change
numbers or letters on the display by just changing
the wiring to the display. Connect the terminals to
form the letters or numbers to terminal 71 (in the
place of the 21 and 23 terminals). Connections for
the number 3 would be 17-21-22-23-20-71.
You can try different values of capacitors to see their
effects. Don’t use a capacitor with a value higher than
10
μF or the excessive current can damage the
transistor.
Notes:
EXPERIMENT #13: VISION TEST
Wiring Sequence:
o 21-23-71
o 25-124-137
o 40-73
o 41-72
o 82-83-42-119
o 74-81-111
o 84-112-138
o 121-122
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Schematic
This experiment uses the LED and an audio oscillator
alarm to indicate three different levels of water in a
container. The water is used as a conductor to
complete the circuits and show the water level.
When the water is below all three of the wire
connections, only the bottom segment (D) of the LED
is on (indicating a low water level).
When the water is at a level that touches the two long
wires connected to terminals 77 and 124 (but is below
the shorter wire), the base current turns on transistor
Q2 and the middle segment of the LED (G) turns on
(indicating a moderate water level).
If the water rises to a level high enough to touch all
three wires, the base current is supplied to transistor
Q1, and the top segment of the LED (A) lights. The
audio oscillator is also activated as a warning of a
high water level.
Of course, you can alter this wiring to make the LED
display show other letters of symbols to indicate the
different water levels. Can you think of any other
symbols? (How about L = low, C = center, and H =
high?)
Notes:
EXPERIMENT #115: WATER LEVEL WARNING
Wiring Sequence:
o 1-29
o 2-30
o 3-103-109
o 4-17-41-87
o 5-47-110
o 20-42-45-119
o 22-44
o 25-48-124-WIRE
o 40-76
o 43-78
o 46-104-88
o 75-WIRE
o 77-WIRE
o 121-122
Schematic