McCreavy
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This morning there was a team building exercise at the District Executive Committee meeting.

It was called the "Marshmallow Challenge" and each participating team gets a brown paper bag with:

20 sticks of spaghetti A piece of string Masking tape A marshmallow and has 18 minutes to assemble a free-standing structure supporting the marshmallow. We had about 10 teams of 4 people each.

According to the official rules on the marshmallow challenge site, each team is supposed to get one yard of tape -- for our version, each team got a roll of masking tape. The rules we were given specified we weren't allowed to tape the spaghetti to the table, but nothing about not using the tape roll itself. This played well for our solution.

When the 18-minute clock started, our team spent the first few minutes inspecting our supplies and considering our options. A "tee-pee" was what we decided to go with -- it was going to take too long to assemble girders out of the spaghetti.

We made five or so rods of three spaghetti sticks each and started assembling. The tower wasn't and we started wrapping it in lengths of tape and then the roll itself came into play: securing the tower to the roll made it really stable.

We continued to build another two levels of sticks on top of our 3-stick tall tower when we got the two minute warning. Looking at other people's towers, we had no chance of winning -- they were big gangly structures with struts and crossbars and a lot of airy height.

At around the 1 minute warning, people began installing their marshmallows atop their towers -- and that's when it got fun. There was a lot of crumpling going on in that last minute!

Our tower was also too tall -- we couldn't balance the marshmallow and it looked like all was lost.

In the last 15 seconds or so, I made a quick executive decision to behead our tower by two sticks of spaghetti... losing the top 25% of height. We smushed the marshmallow on top of the resulting spike. It stood!

The Buzzer sounded and we looked around.

Of the ten teams, there were about 6 towers standing. Two of them were disqualified due to being taped to the desk. One collapsed before it could be measured.

Of the remaining towers, ours was tallest by a few centimeters!

No official challenge was made regarding our use of the tape roll after a judge confirmed it was okay to use "anything in the bag." Instead, we were applauded for our creativity.

What'd I take away? Iterate, cooperate, and marshmallows weigh more than you think.

Also, in the course of this post, I learned "marshmallow" has no "e" in it.


Earlier this week during a trip to Halted, we were talking about how capacitors work. We knew the basics: it's a device to store electrical energy, but we were all bleary on how they worked.

Last night I was talking to a hardware engineer and asked her the same question, and I got the same answer: "it's a device to store electrical energy." I pressed: "that's what a capacitor is -- but how do they really work? Like, what causes a capacitor to release its charge? It's only got two terminals, its not like a transistor -- when/how do they work?"

Here's what I got:

A capacitor has two plates inside it separated by a non-conductive substance (the dielectric). Common substances to separate the plates are: air, mylar, glass, or ceramic.

When you connect a capacitor to a battery, the plate connected to the negative terminal begins accumulating (charging) with electrons. The plate on the capacitor connected to the positive terminal loses electrons back to the battery.

Eventually the capacitor is "charged" when it has the same voltage as the battery and electrons stop flowing. At this point, if you take the capacitor out of the circuit, it'll have a static configuration of pile of electrons on the negative plate (and a dearth of electrons on the positive plate).

Put the capacitor into another circuit, and it'll discharge into it, I found this description of Capacitor Charging and Discharging very helpful.

One thing I'm still not remembering: how can you tell a capacitor is fully charged without shorting it? I think you use a big resistor (to keep it from discharging very fast) and an LED in series.


The soldering iron I've used for years is a Radio Shack $18 deal and even though I always stored it tinned, the tip has oxidized. In its prime, it helped me chip my original PlayStation to play imports, add a WiiKey to my Nintendo, and work around a RROD on my XBox360.

Lately I've been using it to fix R/C motherboards, and its age is showing. It's always taken "a long time" to heat up, but now that time is an unbearable 5 minutes! When it is up to temperature I have to favor one side because there's a bit of oxidation along the point and other side (I always stored it tinned, I swear). Before I try replacing the flaky SID chip on one of my Commodores, I need a better soldering tool.

Instead of buying a replacement iron from The Shack (my cheap iron doesn't have a replaceable tip) for my workbench, I checked the internet and youtube for the latest in home soldering solutions. Wow, things have come a long way: they're called "Hot Air Rework Stations." Sometimes they call them "desoldering stations."

I wish I had had a Hot Air gun when fixing the XBox360 -- it was a nightmare doing that delicate work with an iron. With a Hot Air gun, it would've been a breeze... A hot breeze! Looking at videos on YouTube, a Hot Air rework station is definitely the way to go when working with SMD chips. Resistors, MOSFETs, capacitors... childs play. Using hot air gun to "heat up the set of contact pads with molten solder, applying the device, and then removing the heat" is the way to go over trying to solder each pad individually with an iron.

The popular quality brands in the $100-$200 range I see are "Aoyue", "Hakko", and "X-Tronic." Hakko is the most expensive. Aoyue seems to be the "generic" cheaper version of Hakko. X-Tronic has the most extras and value. I like the name too: the others sound like something a cat might make while coughing up hairballs.

The benefits rework station irons have over my Radio Shack iron are: digital temperature control, fast heating, and replaceable tips. X-Tronic comes with 10 replaceable tips -- the tips I think that'll be most useful are the ones with flat angled surfaces. They look like they'll really be good at applying some heat:

Looking at their site and checking the reviews, I'm torn between the X-Tronic 4040 and the higher end X-Tronic 6040. The 6040 is ~$20 more, but it has a smaller footprint and the control panel has buttons in addition to dials and switches. You can't beat buttons. Also, I like the placements of the power switches on the 6040. Here's a side-by-side comparison of the two versions:

4040 Rework Station (~$120)

6040 Rework Station (~$140)

It looks like the heating element for the Hot Air Gun in the 6040 is "in" the handle, versus "in the box" for the 4040. Not sure which is better, but I'm guessing you have more responsive temperature control with the 6040. Both versions come with a replacement heating elements, which is cool.

I haven't made a decision yet, but I'm edging towards the 6040.


Tags: Soldering
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