science fair box

My daughter decided that she wanted to make something out of electronics for her fourth-grade science fair. For the project, the kids have to come up with a question for which an answer can be hypothesized, and then proven or disproven with an experiment. Elliot, on her own, came up with the question “how does electricity move in a circuit?” This is a rather big question for our limited knowledge of electronics-building in this house, and I wasn’t sure whether we could actually answer the question with a few resistors and some stranded wire. ALas, her teacher approved it. Furthermore, the job was made even more complicated when Elliot’s answer was “I think it is heat.”

I gave Elliot a few books to read, and she took to the Make:Electronics book by Charles Platt. I had bought and/or read a few books before ordering this one and it’s by far the best I’ve found. Apparently, Elliot agrees as she pretty much memorized the first few chapters. I can’t tell you how much fun it is to sit there with a ten-year-old girl and have her thumb through a pile of resistors looking for the 220ohm one as she studies the color codes of the resistor’s stripes. I showed her how to read a multimeter (something I just learned a few weeks ago), and she was off. She built a few simple circuits using the experiments in the book, trying out different values of resistors, various colored LEDs (it was cool when we burned one out and the room smelled like an electrical fire), and four AA batteries.

"Crazy Labs"

It wasn’t long before she was working out ways to have a switch to flip between different colored LEDs, and she asked how to add a knob (potentiometer) to dim the LED. For the science fair experiment, she merely recorded the volts and amps of the circuit with various resistors, and deduced the wattage produced with these numbers. I think she realized what I was worried about with her hypothesis, which was that “I think it is heat” isn’t really an answer to her initial question. The answer has to do with electrons and conductivity and positive/negative forces, but that’s a little deeper than we were able to go with a Radio Shack breadboard.

I wasn’t comfortable sending her to her science fair with the breadboard and all these wires and things (fourth grade boys can be jerks you know), so using one of the circuits she’d worked up, we got a small plastic box from Staples and I soldered the circuit together using a bigger battery (9v) and a stronger potentiometer (50k), along with a huge switch.

Elliot's science fair circuit

(This is the circuit before soldering it to a circuit board and putting it the little clear box to the left. The big switch flips the red or green LED on and off, and the knob thing dims the red LED.)

the science fair box

the science fair box

I was pretty excited when I turned it on last night and it worked. So excited, in fact, that I made a little movie with music from the modular synth.

Now I’m really starting to make plans for odd little projects for myself. For instance, I would like to have a small module for my synth with two clock sources, each voltage-controlled, and have a switch which can sync them or let them run free. I found some plans online for one that uses a basic 555 timer chip, so I think that might be my holiday project…

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