of the battery holder, while the positive terminal
(+) is soldered to the middle contact on the
SPDT switch. The closed switch contact of the
SPDT switch is then soldered to all of the
circuit’s V+ connections, including the anode pin
bus that was created in Step 3.
Insert a 3V lithium coin cell into the battery
holder and switch the circuit on. If none of the
LEDs are illuminated, slowly rotate the
potentiometer. When the pot is turned to one of
its lower positions, the first LED (LED 1) will light
up. In dot mode, one LED will light for each
voltage increment increase throughout the travel
of the potentiometer’s wiper. Near the top of the
LED bar graph, LEDs 8 and 9 will remain lit
throughout the rest of the potentiometer’s
voltage range. When the equivalent of LED 10 is
accessed with the pot, the two blinking LEDs will
start flashing.
Now, all you have to do is add some whistle
and explosion sound effects. At least you won’t
have to worry about being bugged by pesky
mosquitoes, plus you can select your own
musical accompaniment. That’s a win-win. NV ■ Wiring diagram.
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PING)))
ULTRASONICDISTANCESENSOR
July 2014 47