Elenco 130-in-1 Electronics Playground - Manual (Page 54)

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R-S does not mean Radio Shack ® flip-flop. As we
mentioned earlier circuits that flip-flop alternate
between two states. Those who use flip-flop circuits
most often are engineers, and they use flip-flop
circuits to switch between low (0) and high (1)
outputs. We say a circuit is at set status (S) when the
output is high or on. We use the word rest (R) when
a circuit is off.
Once you have completed the wiring, to turn the
power on turn the switch to A. LED 1 or LED 2 will
light up. Touch terminals 13 and 14 in turn with the
long wire connected to terminal 26. What occurs to
LED 1 and LED 2?
The R-S flip-flop is set when the LED 2 lights. The R-
S flip flop is in reset when the LED 1 lights. Set or
reset the flip-flop, then remove the long wire from the
circuit and see what it does.
Now you can observe one of the primary
characteristics of the R-S flip flop. Once you have the
circuit either set or reset, the circuit stays in the
specific state until an input signal causes it to
change. This means that R-S flip flop can remember
things. Advanced computers use similar circuits to
remember things.
Notes:
EXPERIMENT #38: “R-S FLIP-FLOP” USING TTL
Wiring Sequence:
o 77-75-49-31-34-131
o 33-53-52
o 36-55-51
o 50-76-13 (SET)
o 54-78-14 (RESET)
o 121-62-60-59-57-56-LONG WIRE
o 119-132
Schematic
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Here’s another siren that alters its pitch. The siren we
built in our last experiment alters pitch from low to
high, but this one alters its pitch from high to low and
finally stops making any sound. When it stops, press
the key and the siren sound will start again.
Set the switch to position B and put together the
circuit. When you finish the wiring, slide the switch to
position A to turn on the power. You hear a high-
pitched siren sound that becomes progressively
lower, it sounds like a falling bomb. Press the key to
start the sound again.
Like the siren in our last experiment, this siren uses
IC 1 as a buffer and IC 2 as an astable multivibrator.
The capacitor C and the resistor R change the pitch
of the siren sound. The pitch adjusts slowly when you
increase the values of C and R, and adjusts quickly
when you decrease their values. Try using the 3.3
μF
capacitor for C and notice how the pitch changes.
Notes:
EXPERIMENT #88: FALLING BOMB
Wiring Sequence:
o 1-29
o 2-30
o 3-116
o 5-84-94-106-70-121
o 63-113-131-138
o 64-90-92-115
o 65-105-89
o 66-82-83-91
o 68-67-81
o 93-69-114-137
o 119-124
o 122-132
Schematic