Elenco Electronics 202 - Manual (Page 100)

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Project #237
OBJECTIVE: To introduce you to the OR concept of electronic
wiring.
Build the circuit shown. Notice that if you turn on the slide switch (S1)
OR press the press switch (S2) the LED (D1) lights up. There is no
partially lit state here, the diode is either totally on or totally off. While
this may seem very simple and boring, it represents an important
concept in electronics. Two switches like this may be used to turn on
a light in your house, or they might be two sensors at a railroad
crossing used to start the ding-ding sound and lower the gate. You
could also have more than two switches and the circuit would function
the same way.
This OR That
Project #238
OBJECTIVE: To introduce you to digital circuits.
Build the circuit shown. Notice that if you turn on the slide switch (S1)
AND press the press switch (S2) the LED (D1) lights up. Once again,
there is no partially lit state here, the LED is either totally on or totally
off. Two switches like this may be used to turn on the same light in your
house, the room switch and the master switch in the electrical box. You
could also have more than two switches and the circuit would function
the same way.
Combinations of AND and OR circuits are used to add and multiply
numbers together in modern computers. These circuits are made of
tiny transistors in massive integrated circuits.
This AND That