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wood electronics case
Tuesday, February 22 2011
Today I built a case to house my new Arduino-based solar controller (Solar Controller III). In the past I've been pretty good at improvising cases from salvaged equipment. Solar Controller I was housed in a old external modem, though Solar Controller II had taken up residence in a "project box" I'd bought at Radio Shack. I took a different approach with the case I made today, using mostly 5/8 inch thick planks of wood with simple butt-joints that I both glued and screwed. The problem with wooden planks is that they are too thick for mounting most connectors, so on one side I used a scrap piece of Corten steel which into which I cut holes for my two main connectors (a D9 for serial communications and a D25 for sensor and actuator wires). Since the steel was over a sixteenth of an inch thick, cutting out holes for the connectors ended up being a substantial drilling and filing job. It was the first serious use I'd yet made of a small vise I'd installed on the westmost of the two oak pillars in the laboratory (these carry the weight of the solar deck overhead).
I also added a switching AC power supply to the new controller (salvaging one from an old DSL modem). The power supply consisted of a small black brick with a standard "shroud female" AC connector. By cutting a hole in the new case the size of that brick's cross-section, I could slide it in flush, where it would be black rectangle with a shroud female AC connector on it. Despite my crude methods and materials, the result was handsome in steampunk kind of way, which is kind of a shame considering the controller will end up in the boiler room, which is about as different from an art gallery as an indoor room can get.
Some weeks ago I discovered that a good way to power a laptop was to simply attach its DC barrel connector (the most common kind of power connector on a laptop) to 12 volts provided by a standard desktop power supply. That worked so well and with such efficiency that it was possible to remove the fan from some power supplies to achieve both silence and reliability. This had me convinced that standard PC power supplies are perfect for providing power in any application. It turns out, though, that this is not the case. For one thing, most PC power supplies require a certain minimum draw in order to operate at all. My solar controller uses two watts when its LCD is backlit, one watt when it is not. That, as it turns out, is not enough to cause any PC power supply to turn on. The other issue is efficiency; a PC power supply seems to use one or two watts on its own no matter what is happening in the equipment attached to it. This wasn't the case of the small DSL modem power supply I ended up using to supply the controller.
efficiency
For linking purposes this article's URL is:
http://asecular.com/blog.php?110222 feedback
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