Elenco Electronic Playground 50-in-1 Experiments - Manual (Page 66)

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Now that you’re familiar with the flip-flop, let’s introduce
some more digital circuits. Digital circuits are circuits that
have only two states, such as high-voltage/low-voltage,
on/off, yes/no, and true/false. Connect the wires
according to Wiring Checklist. Take a look at the
schematic, it is very simple. Wires X and Y are
considered to be digital inputs, so connect them to either
the battery spring 27 (9V, or HIGH) or leave them
unconnected (this is the same as connecting them to 0V,
or LOW). Test the four combinations of X and Y to
determine the state of LED1 (ON or OFF), filling in the
table below: This type of table is called a truth table. From it, you can
see that if X
or Y is HIGH then LED1 will be ON. Hence,
this configuration is called an OR gate. X and Y might
represent two switches to turn on a light in your house.
Or they might represent sensors at a railroad crossing; if
either senses a train coming they start the ding-ding
sound and lower the gate. You could also have more than
two inputs, by adding more parts to your circuit and more
columns to the truth table.
EXPERIMENT #47: This OR That
Wiring Checklist:
o 17-to-20-to-26
o 42-to-1
o 2-to-16-to-19
o 15-to-44
o 45-to-unconnected
(this is referred to as wire X)
o 18-to-46
o 47-to-unconnected
(this is referred to as wire Y)
o 43-to-27
Schematic
Wire X
X Y LED 1
LOW/UNCONNECTED LOW/UNCONNECTED
LOW/UNCONNECTED HIGH/POWER
HIGH/POWER LOW/UNCONNECTED
HIGH/POWER HIGH/POWER
Wire Y