Archive for June 2010

Yesterday was busy time at the house, with Cliff the builder, Jarrod the joiner, Jarrod2, Paul the plumber, Bruce the sparkie, Bruce’s apprentice, and myself. Thus lots got done – we have fascia on the eaves, wiring upstairs, most of the plumbing and gas in the walls, a stack of timber crib, and chases mostly cut into the concrete walls downstairs.

Thus by this weekend, we should have every service we need installed into the walls and we’ll be ready for the insulation. This is currently sitting in big bags all over the place and generally in the way. It’s wool and unlike fibreglass, it’s lovely to handle.

So, here’s an advance request for assistance on saturday, cutting wool to shape and fitting it into the walls. Weather looks passable, but hey, we’ll be inside, with windows and ever-increasing amounts of comfort.

After seeming ages without much feeling like there was progress, this week the house took a jump towards feeling like done. The windows finally arrived. They are reasuringly solid, to the point where I spend so much time opening and closing them, just to feel the mechanism, that I hardly took any detail pictures.

This also means we can no longer use the excuse that it’s raining and thus we don’t have to get out of bed.

So the place is nearly closed in. There’s still a couple windows more to go, and we’ll need some doors at some point, but now it’s comfortably pleasant inside. Hell, we actually have an inside, rather than just some walls and a roof. Next up is the sparkie, insulation, then gib walls, and earth plaster and floors. Oh, and another retaining wall.

Saturday was oiling, with assistance, and wearing out the diamond saw cutting chases for electrical conduit. Tip for the future – when the diamond saw starts cutting badly, the edge heats up to a bright orange, and sparks of molten steel come flying off and burn your forehead, that’s when you know that you’ve worn off all the diamond on the blade. I spent all of Sunday cutting notches in cribs with Cliff’s setup. Imagine a slot, 10 mm wide, 10 mm deep. Now cut a hundred metres of that, 50 mm at a time. There’s more to do, he sighed.

Lithium batteries questions

So work is continuing on the glow fans. I find myself wanting to run the next version off lithium batteries, but I’m a bit confused. Ok, overcharging them is bad, so I’ve a design for a proper charging circuit, based around the Linear LTC1734. And that’s all well and good.

Discharging them is another matter, with dire warnings for letting the battery voltage get too low. However, here is where I get confussed. Surely whatever circuitry that is responsible for monitoring the shutdown is going to draw a load? Is it the case that so long as the load is low, then the battery won’t be damaged? How low?

Current plan for the low battery behaviour is to have the Picaxe wake up once every umm.. few seconds, check that charging hasn’t started, make sure that everything else is off, and then snooze again for a while. The Picaxe gets its 5V from a charge pump converter (a MAX1595) with a 0.2 mA draw when the Picaxe isn’t drawing power.

(I think this is the main power draw when off. There’s other gubbins – the other step-up converter to power the LEDs draws only 5 uA when shutdown, but needs a pull-down resistor to keep it shutdown, which will have it’s own current needs. But I think all that should be much smaller than the 200 uA from the charge pump.)

Is that all I need to do? Just have the Picaxe mostly off and a 0.2 mA draw running on the battery? Or are there better ways to do this? And yes, some lithium batteries come with under-voltage protection built in. If under-voltage is so bad, why don’t they all? And why can’t I find an undervoltage protection chip for just one lithium cell, instead of the 2-10 that TI offer.

Brain all hurty now.

House pics for another month

Err… yeah, another month between house pics. I blame the dire weather and that we’ve been doing thoroughly non-photogenic things. Come on, shoveling gravel into holes? Here’s a picture of some flat, well-drained ground, lots of work by lots of people might have gone into it, but it doesn’t look too fancy.

Anyway, we have weatherboards:

And I’m told we have windows as of yesterday, but no pics yet.

I have been mocking up the light shades, what’s cardboard here will be recycled copper:

Hey, guess what? We’ll be working at the house tomorrow and probably sunday. Now that we have all of walls, windows, and a roof, we’ll be up there no matter what the weather. Any assistance welcome, and we’re having a competition for the amusing excuses for why you won’t be there. I’ll start with one policy analyst who this morning said “tomorrow I have to sand a boat, sunday I’ll have my lungs full of glass fibres and next weekend is right out on account of death by glass fibre inhalation”.

Random learnings from this weekend

1) The diggability of the earth at our section varies from beautiful gravel to the devil’s own clay. Shoveling the gravel makes you think that all the world’s problems can be solved with a little hard work. It takes to a shovel, goes where you put it, and stays there. However, shoveling the clay involves kicking the shovel into the sloppy mass, levering away to break out a chunk from a hill with the consistency of treacle, and finally getting that chunk free from the rest only to have it roll off the shovel blade and re-glue itself as firmly as if you’d never bothered. This leads to the conclusion that all human endeavour is futile and you might as well just go and shoot yourself.

2) MAX16836s look to be lovely little chips, kicking out a nice steady 350 milliAmps to drive blindingly-bright LEDs. Most similar drivers are buck-type, needing an inductor, diode, and other random crap to clutter up a circuit board; the MAX16836s just need two tiny capacitors. Thus I want to get my hands on them. Sadly, NZ’s main distributors (Farnell, RS) don’t stock them, the overseas distributors (Digikey, Avnet) have a minimum order of 248, and Maxim will sell direct, with a $50 handling fee on a $2 chip. I have resentfully begged Maxim for samples.

3) The next shiny things that I make will have lithium batteries, not NiMH, for the simple reason that the USB battery charging specification is gibberish. Seriously, “Battery Charging v1.1 Spec”, Section 2.2.2: “Any USB device is allowed to draw a current of ISUSP for an unlimited amount of time from a Downstream Port when not connected.” What? A USB device can use power from a computer that it doesn’t have a connection to? Either the USB Consortium can break the laws of physics, or those words do not mean what you think they mean. Anyway, all the required specification decyphering has been done by companies making battery charge management chips, but only for lithium chargers, not NiMH chargers. So I’m choosing batteries based on whether I will need to understand the specification for how I’m going to be plugging them in. And that’s just odd. Still, this should give me more power density, charging from any USB port, and a slim but non-zero chance of shiny things catching fire.

4) Last week’s policy realisation could be the realisation that everyone gets to once they’ve spent five years in policy and been around the ‘problem=>solution=>oops, new problem’ loop. Said realisation is that any strategy is merely a point-in-time approach to formalising an on-going set of problems, in the hope that will make solutions obvious. In reality, we don’t need strategies, we need strategic capability, i.e. the ability to think about problems in an enduring way, so that we can find some enduring solutions.

This isn’t helped by the tools we have for communicating, especially when we’re communicating about the real world, and specifically any time that someone talks with an organisation, rather than simply buying something from an organisation. Far too many IT tools are transactional and crap at representing on-going relationships. More here on this, in the context of ticketing and problem-report systems, from the Yorkshire Ranter, which should be required reading for all IT geeks who think IT should be useful in the real world.

And some vids, to summarise what I’ve been up to for a while

I’ve been working away at some prototypes. The glow fans are motion responsive, with a 3-axis accelerometer controlling the colour and brightness based off how they are moved. 10 LEDs, so decently bright too.

I’m working away at making these good enough to be sellable. Right now, the cost for each would be silly and the reliability… well, let’s just say the testing by tatjna & tieke revealed a few issues, but that’s what prototypes are for:

Vids of the glow fans and the Mitochondrion

Sea level rise – bonus impacts

One of the extra impacts from sea level rise is that the spin of the Earth will slow down. The melting of polar ice sheets is already moving weight from the poles into the oceans, which generally are not at the poles.

We’re losing about a gigatonne of ice per day, roughly a cubic kilometre (give or take quite a bit). This is a reasonable chunk of ice now melted and heading towards the equator. Still, the Earth weighs about five million billion gigatonnes.

The overall effect depends upon what ice melts, and where the water ends up in the oceans, coz the oceans are not that flat, overall. So the numbers are pretty vague right now. A metre of sea level rise might lengthen each day by maybe 0.01 seconds. For comparison, the eearthquake that caused the Asian tsunami to lengthen by maybe 0.000002 seconds. So 0.01 seconds is huge, as these things go.

(Also, 1 metre sea level rise means approximately 100 million people homeless, give or take err… quite a lot.)

“The reality is simple and stark. Israel is the target of a massive information war, unprecedented in scale and scope. This war is being waged primarily by a massive consortium of the international Left and the Arab and Islamic worlds… This war is nothing new. It has been going on since the dawn of modern Zionism 150 years ago. In many ways, it is just the current iteration of the eternal war against the Jewish people.”

And that’s from the Jerusalem Post, Israel’s largest English-language newspaper. If this is the Israeli position, then I don’t see this ending well. Hell, it’s not going well and hasn’t for quite some time.

For reference, the Gaza Strip is about the same size as the Hutt Valley. One and a half million people live there. Israel (and Eygpt) control the supply of food, fuel, electricity, and medical supplies. No other trade is allowed, the economy has collapsed, over a million people survive on food aid.