Monthly Archives: May 2012

DIY, Green, Technology

Micro PV two years on.

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Some changes since last year. Firstly the panels have a different orientation from last year.  I moved the shed last August/September and both panels are now facing South West (220deg), still at the tilt of about 5-10 degrees (which I really must measure), not ideal but better than before.

The same two Evergreen panels are in use, but I’ve a new Mastervolt Soladin Inverter from Nigel in Mysolarshop. Unfortunately I accidentally let the magic smoke out of the Steca, when moving things around and it had to be replaced. I might try and get the smoke back in some rainy afternoon when I’m bored. The measurement set-up is still the same using the Envi CC-128.

So for the last 12 months rrdtool is saying an ‘average’ of 28 watts is produced every day. So from the back-of-an-envelope, we get 0.028*24*365 or approximately 245 kWh produced, with a value of approximately €49.

However, I have reason to believe that output will be better this year. The first picture below is from the 3rd of June last year.

This one is from today:

Two things are immediately obvious. The peak instantaneous value, and the average are both higher. This should help increase the output from the system for 2012.

The experiment continues!

General, Technology

The Kilogram

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So I thought I knew what a kilogram was until I read this.

Photo: Robert Rathe/National Institute of Standards and Technology

Once a year, three officials bearing three separate keys meet at the bottom of a stairwell at the International Bureau of Weights and Measures, in Sèvres, France. There they unlock a vault to check that a plum-size cylinder of platinum iridium alloy is exactly where it should be. Then they close the vault and leave the cylinder to sit alone, under three concentric bell jars, as it has for most of the past 125 years.

“So what?” you say.

The trouble posed by the master kilogram is apparent in the many friction-filled steps by which it calibrates other masses. Once every few decades, a scientist plucks the cylinder from its perch with chamois-leather-padded pincers, rubs its surface with a cloth soaked in alcohol and ether, and steam-cleans it. Then he puts the prototype in a precise balance that compares it to the bureau’s official copies, which are in turn compared to copies kept by member countries. And thus the prototype’s mass trickles down to set the standard for the rest of the world.

The system has been far from seamless. When the cylinder was last removed from the vault in 1988, the bureau’s metrologists were disappointed to discover that its mass and those of its official copies had drifted apart by as much as 70 micrograms since 1889. That discrepancy is tiny—comparable to the mass of a small grain of sugar—but it confirmed a troubling instability. All that metrologists can say is that the master kilogram seems to have lost as much as 50 µg over the course of a century relative to its siblings. But the actual drift could be up or down, and it might even be a lot more than 50 µg, because the prototype and its metallurgically identical copies could all be changing as an ensemble.

It is a long article, but worth a read.

Amateur Radio, Computing

iPod and “Keys out of order”

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So, its a typical weekday evening, I have several things waiting to be completed, but earlier on today, John, EI7BA posed a question on a mailing list looking for some information about a piece of software.

He wanted to know if it would work with his FT-847, and, I have the same transceiver here so I thought I’d help him out by trying to use the software in a Windows Virtual Machine running on my Mac-mini.

First problem, the mini is at the wrong end of the desk, about 7 feet from my FT-847. So I slide the mini and all attached to it along the desk to make up the shortfall, all good.

I test the software, and it seems to work ok with the 847, report the same to EI7BA, all good.

Now, what exactly happened I’m not sure, but I saw my iPod display light up, thinking it a bit strange, I picked it up and pushed the docking connector home again, all good.

iTunes gives me an error when it tries to sync, hmmm, Disk Repair says it can’t be repaired, hmmm, I tried to fsck it in the terminal


bash-3.2# fsck_hfs -fy /dev/disk1s2
** /dev/rdisk1s2
Executing fsck_hfs (version diskdev_cmds-540.1~34).
** Checking Journaled HFS Plus volume.
The volume name is John's Pod
** Checking extents overflow file.
** Checking catalog file.
Keys out of order
(4, 3045)
** Rebuilding catalog B-tree.
** The volume John's Pod could not be repaired.
bash-3.2#

Not good. I tried to mount it, but it refuses to mount, not good. The perceived wisdom on google is to purchase Disk Warrior. I have a few GB of data on there that I don’t want to loose, but it’s not really worth spending money on, so after a bit more trawling through web pages I decide the data is gone (not good), but I will be able to gather it all together again, given time.

Before I “restore” the iPod, and purely for the hell of it I plug it into my Roadkill (I first heard Bill, N2CQR use the term) Ubuntu Laptop. Lo and behold, the drive mounted automatically.

I immediately remounted it read-only and started copying off data.  That seemed to complete successfully, so I unmounted the drive and plugged it back into the mini. Much to my surprise, the drive mounted (and iTunes was happy to sync it).  Just to check, I tried an fsck again and it still gave gave the same errors as above. For now, I’ve decided to ignore the errors until such time as it stops working completely.

So, if you have an iPod that gives you a Keys out of order error message when you try to check and/or repair it, talk to a friendly Linux user and ask them if you could plug your iPod into it before you decide your data is toast.