Elenco Electronics EP-130, Руководство пользователя

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Carefully compare the schematic for this project with
the schematic for the last project. They are similar in
many ways, but there’s an important difference.
Do you see what it is? Better still, can you tell what
effect the difference has on the project’s operation?
Try to figure it out before you build this circuit.
Connect the earphone to Terminals 13 and 14 and
set the switch to position A. You should find that LED
1 lights up, but you hear nothing in the earphone.
When LED 1 turns off, then you hear a sound in the
earphone.
Try to figure out why this happens. Study the
schematic and when you think you have the answer,
read on to check your guess.
When the output of the NAND multivibrator is 0,
current can flow through LED 1 to light it but the
transistor multivibrator won’t work because the left
transistor has a 1 signal applied to its emitter. When
the output of the NAND multivibrator is 1, LED 1
won’t light but a 0 signal is applied to the emitter of
the left transistor. The transistor multivibrator can
then work, and you can hear the sound in your
earphone.
Notes:
EXPERIMENT #54: SON OF BUZZIN’ LED
Wiring Sequence:
o
131-45-31-49
o
116-76-56-57-55
o
40-109-85
o
42-58-33
o
43-105-81
o
50-51-77-115
o
52-53-54-75-78
o
72-59-60-62-80-82-86-121
o
119-132
o
44-110-71-13-EARPHONE
o
41-106-79-14-EARPHONE
Schematic