Elias presents ... a worm!    Thoughts on family, philosophy,
and technology


Wednesday, November 04, 2009

Electronics Project #1

Since recently completing all 101 projects in the Snap Electronics Jr. kit, Elias has been learning real hobby electronics and loving it. It's almost an obsession, but healthy I think. We have fun and learn a lot together. What makes it natural for him is he is able to retain just about every fact ever explained to him, and he is very excited to learn how physical things work and above all to create his own contraptions. It surely helps that I'm interested in electronics too (cause like all geeks I want to eventually build super-cool robots), though I actually know very little about it.

We've been reading that Forest M. Mims, III book Getting Started in Electronics that Radio Shack has been selling for at least 20 years -- that's how old my copy is. We're up to Silicon Controlled Rectifiers. And to test out our little circuits we use a bread boarding box that I've been storing for 20 years, apparently just for this purpose. Last week, Elias got the hang of creating what he calls a "touch detector" circuit, which involves a transistor, a resistor, an LED, and some wires. I don't even know how (are people positively charged relative to residential ground?), but just by touching one wire attached to the gate of the transistor, the LED lights up. He was building this all by himself on the bread board for a few days.

I recommended that we get out my soldering iron, another relic, and actually burn his touch detector circuit into permanent form. We had a broken circuit board from an old phone handset that was just the right size for 2 AAA batteries to lay on it. Of course I did all the soldering, but only after I had him draw a schematic of what we had laid out on the bread board. He labeled the 10K Ohm resistor, the round and flat sides of the LED with little marks, and the 2N2222 transistor, which has E, C, and B by its legs. The three "fingers" on each of the two free ends of wires are, I think, a reflection of his love earlier this year for drawing diagrams of neurons, after seeing them in my college biology text. Here's the last version he made on the breadboard, touching the red and green wires lights the LED.

And this is the permanent version. Bending the white wire slightly so that it touches a leg of the transistor lights the LED. We found that once we went to battery power, the mysterious trick of just touching the transistor gate with your finger no longer worked.

What next? We are trying to build a circuit from the Mims book that is supposed to pulse a light or buzzer at about 1Hz. One capacitor, two transistors, and three resistors. He laid most of it out on the bread board looking at the schematic, then I stepped in to finish it. You'd think I could nail such a baby circuit, but we were working on it tonight and it just buzzes solidly. So I know the first thing Elias is going to ask me tomorrow morning is to work on it with him. Fun!

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