procrastination diagram

If you have much experience with air conditioners, you probably know of them "icing up", where ice forms on the (cold) coils that are facing you (which are called evaporators, see below). One of the air conditioner units in the house has been icing up for a slightly entertaining reason, so I figured I'd write about it this week.

Air conditioners work by using a compressible refrigerant to transfer heat (generally) "against the grade" from a cooler place to a warmer place. The refrigerant is compressed, and sheds heat as it liquefies in a set of heat-exchanging coils (usually outside) called the condenser, pumped indoors to a set of coils called the evaporator, where it turns into gas, picking up heat. (A note about the refrigerant: generally, these days, they're made up of complex hydrocarbons with fluorine (and chlorine in older systems, usually Freon, which is a trademark for any of several chlorofluorocarbons), although there's this thing called an EcoCute that uses carbon dioxide...)

Anyway, air conditioners ice up because they can't move enough air across the evaporator coils to keep them warm enough to avoid freezing water out of the air. So, if your air conditioner is overpowered (and the temperature is already too low in the space you're trying to cool), it will ice up. (Icing up is bad because if there's no heat for the refrigerant to absorb, it won't turn into a gas, and may damage the compressor.) If it's low on refrigerant, the expansion-to-a-gas stage will absorb too much heat, and it will ice up. Most commonly, though, if airflow is blocked, it will freeze for very obvious reasons.

What we're experiencing is pretty clearly the last problem, although before I explain it fully, I should mention the dehumidification effect of air conditioners (which is, to be sure, my favorite part). It's pretty straight forward; the evaporator gets cold, so water condenses on it. Air conditioners should have drains to deal with runoff condensation. Our building is three floors, each of which has an air conditioner. They're stacked, and they share a drain. Unfortunately, something's gone wrong with the drain, and the upper floor units have been draining _into_ the first floor unit, which gets it's air filter waterlogged, and, well, a waterlogged filter doesn't pass air too well..

I find this failure mode funny for some reason. I'm not sure why.

It's Monday morning and it's time for the inevitable disconnected glob of internet.

The Shruthi-1 is/will be a small build-it-yourself synthesizer that actually sounds really cool.

Nyle Steiner K7NS explains how to build a TEA laser out of common household materials and a 6kV power supply. (That last item is /mostly/ why I haven't whipped one up this evening).

A huge pile of technical information on the Ensoniq ESQ-1 and SQ-80 synthesizers from the 80s. Just why I have this tab open is perhaps best left as an exercise for the reader, but I can relate that I really wanted one of these when I was in high school.

They can certainly be found elsewhere for cheaper, but these 12VDC 2A switching wall-warts are impressive little beasties.

PVC fittings for structure rather than fluid flow.

Synth DIY pages with lots of discussion of hybrid techniques and how various notable instruments differently wire up the once common Curtis and SSM voltage-controlled module chips.

A Chrome extension that displays PDFs in the browser via google docs.

A fascinating piece written in a 19-tone equal-temperament scale.

Implementing non-recursive makefiles.

Are you sitting comfortably? Have you checked under your seat for the license agreement? Did you bring your coat?

ARM came out with a neat little peripheral-packed toy embedded system called the mbed. It costs $59 and has approximately all the IO you could possibly want, including Ethernet. It also has an online compiler, and a clever bootloader that knows how to look like a USB disk, so that you can develop for it even if you use one of those weird free operating systems.

The New York Times was quick to pat them on the back, but the backlash was also quick to appear (I'm particularly amused by the people who seem to be worried that the bootloader software was "licensed and not sold"... just like all of this free software that people seem to like is license and not given away). People's primary objection seemed to be online compiler, but there's instructions for setting up a compiler locally, although then you don't get to use their libraries. I'm not sure I'd want to, to be honest.

I speculate that ARM's bootloader is not open-source because it probably licenses Microsoft's intellectual property in order to provide/read the filesystem for the virtual disk. While I think those patents are a little bit questionable, I can't really blame ARM for not wanting to rock the boat-- and the functionality they provide is still potentially useful to me.

Now I just need to figure out a "thing" that needs to be of the internet...