Archive for March, 2010
Alternative Fridge-Freezer Anomaly Explanation
by mark on Mar.27, 2010, under Solar
This explanation is probably wrong because you would expect a deadzone in the power/current quantization levels to stay the same. However, what Ive observed is that the anomaly remains even when the base power varies by -50W to at least +2kW. I believe this precludes the previous explanation because this scale invariance should not exist under these circumstances if the dynamic range switching premise holds, which I still believe to be the case.
A better but not intuitive explanation is that the mechanical vibration of each unit alters the behaviour of the other, increasing the total VA (since that’s what the current sensor measures). The 2 units are located next to each other so are mechanically coupled through the floor.
Of course this explanation could be wrong too but I can’t think of another ATM.
Migrating Windows User Ids
by mark on Mar.12, 2010, under Windows
There are times when domains on windows change and thus your user id changes. However, you may have lots of files owned by you that are not in your user dir. Migrating these user ids to you new one, I’ve found, is not too difficult after all.
All you need is a tool from microsoft called subinacl.
Download and install the msi. Install path is
C:\Program Files\Windows Resource Kits\Tools\subinacl.exe
So use this for the command name below.
First find your old userid. Use a file you know you used to own. E.g. the projects directory.
Subinacl /file c:\projects /display
Copy and paste yours for use in the commands below
Now for the commands. Do for all drives if you have multiple disks.
The lines below are for me of course so sub in your cut S-xxx and new user id
Subinacl /subdir c:\ /accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\username
also the primary group, which can be found up the top of the display dump.
Subinacl /subdir c:\ "/accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\Domain Users"
all registry keys
Subinacl /subkeyreg HKEY_CURRENT_USER /accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\username
Subinacl /subkeyreg HKEY_LOCAL_MACHINE /accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\username
Subinacl /subkeyreg HKEY_CLASSES_ROOT /accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\username
(none found, so optional)
and the groups
Subinacl /subkeyreg HKEY_CURRENT_USER "/accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\Domain Users"
Subinacl /subkeyreg HKEY_LOCAL_MACHINE "/accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\Domain Users"
Subinacl /subkeyreg HKEY_CLASSES_ROOT "/accountmig=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx=newdomain\Domain Users"
After you are happy
Subinacl /subdir c:\ /suppresssid=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx
Subinacl /subkeyreg HKEY_CURRENT_USER /suppresssid=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx
Subinacl /subkeyreg HKEY_LOCAL_MACHINE /suppresssid=S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx
When you are finished, everything you used to own you will own again.
Fridge/Freezer Anomaly Explained (Probably)
by mark on Mar.10, 2010, under Solar
I had some more thoughts on the fridge/freezer anomaly previously detailed.
I had read about the 144 Bug. I suspect it is related to this.
This has to do with the way that the transmitter samples the current sensor. I have noticed that the resolution is much better at lower power than higher power. I suspect this is because the ADC reference in the PIC is connected to a PWM output (smoothed of course) to provide a variable dynamic range sampling system. As you would expect, there would be quite a few range change points in the sampling algorithm. The 144 bug details one at 3kW. I suspect there is also one at somewhere between 450W and 600W which is not calibrated correctly. There are probably others too.
If these range change points are known, it would be easy enough to add fudge factors during datalogging to correct for this. Alternatively I could disassemble the transmitter PIC code and just fix it.
No time for this now.
Another possibility is that the sampling system is non-linear, increasing apparent measurements. Not enough calibrated sample points to prove. Anyhow the former is more likely.
Watts Clever Fridge + Freezer Power Anomaly
by mark on Mar.07, 2010, under Solar
I have noticed what appears to be an anomaly in the power presented by my fridge and freezer as measured by the watts clever mains power monitor.
As can be seen, the base load is about 320W which consists of 2 PCs and incidental standbys. The fridge cycles more frequently than the freezer. The fridge power alone is about 75W and the freezer alone is about 100W. You would thus expect their combined power to be 175W. However, this is not so! Measured combined power is about 250W.
Given that the mains power monitor is power factor insensitive, and the compressors of both devices have inductive power factor, this result is unexpected. I’m also assuming that the power factor of the baseload is 1.0, which I think is reasonable as using another power meter showed a power factor of 1 for the PCs and these predominate the baseload.
I would expect the vector sum of fridge+freeze+baseload to be less than the sum of their magnitudes.
Wordpress Install Direct Filesystem Hack
by mark on Mar.05, 2010, under Wordpress
I use
chgrp -R www-data wp-content
chown -R g+w wp-content
To make this work with wordpress, edit wp-admin/includes/file.php in function get_filesystem_method() and comment out
if ( getmyuid() == fileowner($temp_file) )
to
#if ( getmyuid() == fileowner($temp_file) )
If the test file can be written, who cares if it is not owned by the webserver.
You will have to reapply this edit every time wordpress core is updated.
PV Panel Orientation Effectiveness
by mark on Mar.05, 2010, under Solar
This site has a nice image showing PV panel orientation and the expected output as a percentage of optimal orientation at latitude 35°S.

A fully west or east facing panel will still achieve over 80% of the output of an optimally north facing system. This indicates orientation, whilst critical is not a reason to not install them if no available north facing roof space is available.




