An Eccentric Anomaly: Page 1

Ed Davies's Blog

Solar Warm Air Panel: Part 1.5

A minor update on the solar warm air panel. The weather's not been great, windy with big showers, so I've just managed to slot in odd jobs like staining the wood, screwing it all together and fitting the backing insulation.


Solar Warm Air Panel: Part 1

About a fortnight ago I decided a little bit of practical making-things activity would be good for me.

The house I'm staying in has very thick stone walls so the temperature is pretty stable; particularly the downstairs stays around 12°C whatever. The LPG central heating warms the air quite nicely and the stone's all boarded over so the surface layers warm quickly giving reasonable thermal comfort but as soon as the heating is switched off the temperature drops back rapidly. Over the last few weeks it's been abnormally sunny and the upstairs, which is less well thermally connected to the stone, has been quite comfortable, around 20°C, most days with not more than a quick boost of electric heating first thing in the morning in the bedroom I use as an office.

The downstairs, with its high thermal mass and small windows, has not followed along. This is moderately unpleasant with the bathroom down there. Of course, the heating can deal with that but using it just feels wrong when there's bright sunlight falling on the outside of the building. What I've therefore decided to do is make a small solar warm-air collector to lean up against the bathroom window to bring in a trickle of heat in the hope of increasing the average temperature quicker than it naturally would.


Blog Templating


The software used to create this blog writes a number of files: the individual HTML pages, the HTML index files and the Atom feed. Though it's not necessary for the HTML to be well-formed XML I do have a strong preference for it to be. Actually, I'd rather just use XHTML but that's a separate rant.

XML is just text and can be treated as such but there are enough traps for the wary, let alone the unwary, that it's really not a good plan; in particular, when doing template substitution on the text form it is quite hard to guarantee that the result will be well formed. It's much better to handle it as a proper document structure and leave serialization to code which specializes in doing that right. Python has a number of packages for handling XML with varying degrees of power and standarization but I decided to just use the basic xml.dom and xml.dom.minidom for simplicity. The lack of any form of XPath expressions or the like could be a pain in some applications but isn't a problem here. The compromised namespace management is more irritating but I've hived off dealing with that to a separate module avoiding too much grief while accepting some limitations.

The general scheme is to have template documents stored in the Python code as multiline strings and "compiled" to DOM trees on load. For each output document the Python code recurses down the appropriate template tree producing the output by copying most of the template and performing substitutions for elements in a specific namespace.

The template document therefore has a similar flavour to an XSLT Literal Result Element StyleSheet. The main difference is that the values substituted come from Python data structures rather than from an input XML document.


"It's" & "its"

Dear Web,

The words it's and its are distinct and not interchangeable. Abuse rarely produces real ambiguity though it often results in the need to backtrack and reparse a sentence thereby slowing down reading but it does have the benefit of flagging the writer as likely to be careless: a powerful but not 100% accurate initial filter to apply to Internet writing.


Alternative Vote

Next month (on 2011 May 5th) various parts of the UK are doing miscellaneous democratic things. The whole country, though, is voting in a referendum on a change to the electoral system for MPs in the House of Commons (the lower house of the parliament of the UK). The option is to replace the current first past the post (FPTP) system with an alternative vote (AV) system.

I think AV is horribly flawed and in some circumstances even worse than FPTP. Never the less, I'll be voting for it. Firstly, a vote to retain FPTP would be seen as a vote against any form of electoral reform (which we badly need). Secondly, I think AV would normally be slightly less bad than FPTP.

But what do I mean here by "better" and "worse"?


Blog Software

This blog is produced using some home-grown software. It's intended specifically for my own use — that's the point; it should do what I want without all sorts of configuration options for things I don't need — so is very unlikely to be of much direct interest to anybody else. Never-the-less, some design decisions, and perhaps even code modules, might be of interest to somebody rolling their own.

This entry is a brief overview to be supplemented by later discussion of certain aspects.


Scotland's Census

I can't be bothered with the possible faff that might arise from full-on messing with the census but on the other hand it does seem worthwhile to make Lockheed Martin do some work for their money so a little bit of literal truth feels about right:


Walk on Coldbackie Beach

It was pretty grey, drizzling and miserable for most of the morning and early afternoon but dried up later so, not having been out for a week or so and feeling a bit stale, I decided on a walk to try to find the start of a footpath on the hillside across the valley from home. It was not obvious so I carried on down to the beach which was not exactly crowded; there were some footprints.



My horizon to the west is too high (about 7°) to see Jupiter today with the Sun far enough down. Still, Mercury was visible from about 19:15Z onwards, first through binoculars then directly, before it "set" behind a fairly stationary decaying cloud street.

With my pocket camera on a tripod I got:


In the Beginning

What's the literal meaning of the title of this blog?: Eccentric Anomaly. It just appealed to me though I have used the concept a little bit for work purposes.

And why the badger? I have some grey bits in my hair which are fairly randomly organized but used to form a pretty prominent strip down the front. Somebody said that every time he saw me I looked more and more like a badger. This amused another somebody enough to start calling me Ed the Badger. More...