Nuts and Volts - July 2014

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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