November, 2008

Posts
  • Eric Gunnerson's Compendium

    Holiday light project 2008...

    • 1 Comments

    I've been searching for a new project to do for this season's holiday lights. I typically have four or five ideas floating around my head, and this year is no different.

    Lots of choices, so I've had to come up with a "rule" about new projects. The rule is that the project has to be in the neighborhood of effort-neutral. It already takes too long to put up (and worse, take down) the displays we already have, and I don't want to add anything that makes that worse. Oh, and they can't take too much power, because I'm already on a power budget.

    Unless, it's, like, especially cool.

    I had an idea that met all my criteria. It was small - small enough to be battery powered, if I did my power calculations properly, and was going to be pretty cool.

    It was, unfortunately, going to be a fair pain-in-the-butt to build - the fabrication was a bit complex, and the plan was to build a number of identical pieces. Oh, and it required me to choose the perfect LEDs from the 15 thousand that Mouser carries.

    So, I hadn't made much progress.

    Then, one day I was waiting for some paint to be tinted at my local home store, and I came across these.

    They're holiday lights. Jumbo-sized holiday lights.  The bulb part is made of colored plastic, and measures about 7" high. At the bottom there is a large fake lamp socket. Inside of all of it is a genuine C7 bulb of the appropriate color.

    I bought 3 sets, 15 in all.

    To be different, I wanted to build these as self-contained devices, with a separate microcontroller in each of the light bases. The microcontrollers I'm using cost about $1 each, so there isn't too much cost there, but the big challenge is a power supply. Generally, I build a linear power supply, which is simple and performs well, but you need an expensive and bulky transformer.

    There is a way around that, with the reasonably named "transformerless power supply". Realistically, a better name would be the "high-voltage shock-o-matic", because it involves hooking things directly to the AC line, can only supply a small amount of current, is inefficient, and is hard to troubleshoot. Oh, and if one component fails you get 150 volts instead of the 5 volts you were expecting.

    I decided to build one of these, so I ordered up some parts, wired it up, plugged it in, and immediately lost the magic smoke from one of the resistors. Turns out I miscalculated, and I needed a much-more-expensive power resister.

    Thinking about it some more, I decided that since I still needed power to each bulb - and therefore a wire to each bulb - it was simpler to just build a simple system with one microcontroller.

  • Eric Gunnerson's Compendium

    Brilliant...

    • 2 Comments
    I've been doing some electronics recently, and perhaps I'm therefore more likely to treat this kindly, but I have to say that I think it's brilliant.
  • Eric Gunnerson's Compendium

    What's going on now...

    • 1 Comments
    If you want to keep track of what's going on right now, you need this site...
  • Eric Gunnerson's Compendium

    Scary...

    • 3 Comments

    Last Saturday, we were invited to a Halloween party at a friend of a friend. I only decided to go Friday night, so I'd put essentially zero effort into thinking about a costume.

    The wife was going as a vampire (we had a long discussion on what the feminine form of "vampire" was. I tended towards "vampress", mostly because of how silly it sounded), and I thought of doing something that fit together with that thematically. A lame costume that fits together thematically with another one is much better than a lame one that sits by itself.

    After a while, something suggested itself, and things came together pretty well. You can see the results here:

    (Like pilot in the 1950s who had eyepatches to preserve eyesight in their dominant eye in case of a nuclear explosion, I suggest covering one eye before clicking on the following link).

    Pictures

    I'm hoping that it's obvious who I am.

    The party itself was pretty good. The hosts hired a magician who walked around and did close magic to entertain the crowd. He was talented, though frankly given the sobriety of the majority of the guests it could have been me doing the tricks.

    While we were there a few of the ladies took it on themselves to vandalize me.

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