Saturday 26 December 2009 at 07:53 am
I used to refer to the "RMS power" of something. I thought it was a reasonable term and a specific quantity. Turns out that's not the case. Here's an article that sort of explains reason that's not true.
Here's my attempt to try to explain the distinction:
The instantaneous electrical power consumed by a device is the product of the voltage across the input (energy per unit charge) times the current flowing (current charges per second). Multiply those together and you get energy per time, or power (in watts).
If the voltage and current are constant over time, the the power consumed is just the product of the voltage times the current.
If the voltage and current change with time, then the power may (and usually will) change over time. You calculate power consumed at a given instant by multiply the instantaneous voltage times the instantaneous current at that same instant. What's often more useful is to calculate the average power used over time. Mathematically, this involves taking a number of correlated voltage and current samples over a time period, summing the products, and then dividing by the number of samples. The result is the average power consumed over that period.
Now, there is an important simplification that can be applied ONLY WHEN the input voltages and current are sinusoidal and IN PHASE. A weighted voltage and a weighted current can be computed separately, and their product equals the average power drawn. This is simpler to calculate because you're only mutiplying V*I once, not for each moment in time. These weighted values are called "RMS" values which stands for "root-mean-squared". RMS is a simplification to voltage and current separately because they're sinusoidal. There is no "RMS power" calculated; no such thing exists. It's just "average power".
Saturday 26 December 2009 at 05:15 am
I got a turn-by-turn GPS for Christmas, which means that I now have a GPS unit less than 10 years old; I guess it's time for me to join this milennium. I took it for a test drive today, it works pretty well. I'm quite pleased.
(more)
Tuesday 22 December 2009 at 05:26 am
New blog software set up. I haven't imported the old entries yet.
Craig Steffen
Monday 21 December 2009 at 11:54 am
Welcome to the new craigsteffen.net!
Ok...well, so far, it's just like the old craigsteffen.net but with less functionality (a lot of the pages are missing).
So what's happened:
I got a new server at
vps.net, which is neat. It's virtual web hosting with full virtual machines with full Linux OS distributions that you can log into and install and modify packages and stuff, including full ssh access. You also have control panel access through vps.net to be able to shut down, start up, reboot, hard boot and even re-install your virtual machine image through their GUI.
Starting Saturday through Sunday afternoon, I moved the DNS settings over so that craigsteffen.net the domain name points to the new host. It would have been faster but something went wrong. It's probably related to the fact that I've owned that hostname for like 9 years, and
my domain registrar, Domainmonger, has upgraded their software at least once during that time, and in all that time the configuration for craigsteffen.net remained largely unchanged. When I used their web form to change the configuration, something broke. I'd like to thank them here that in an exchange that took only 3 e-mail messages each direction, they realized there was indeed a problem, passed it of to an expert, and had it fixed within a couple of hours of realizing the real problem on a Sunday afternoon. For a low-priority web site, I consider that excellent. And they're cheap! $17/year per domain.
So as of last night, the DNS was correct and propogating. I got the incoming e-mail all set up as well, so that was working last night before I went to bed. I don't have the outgoing mail set up yet, but that's not critical at the moment. I put up a plain text front page explaining that things were in transition and to be patient.
I also, I think mostly have my old blog back up on the site. That was easy, because even though I compose on blogger, I've always hosted my blog site itself on my own web host.
And I think that I've mostly configured blogger to upload to the new site properly, and sorted out the directory permissions. If this entry posts then we're most of the way there. However, for a long time I've been toying with getting newer/better blogging software, which I was going to get to REAL SOON NOW as soon as I had better web hosting. Well, I have the better hosting now, so it's time for me to graduate to real blogging software.
I'd always thought that I'd use
slashcode, the system that
slashdot uses for their news site. However, I went to look at the slashcode site and they seem to have branched it, and I'm not sure the branch is mature enough that I want to fool with it. Slashcode is heavily database-based, and rests on perl, so I was never sure how I'd get along with it. However, that seems not be be a problem since I probably not going to use it.
Doing searches last night, I ran across a couple of pages that have a feature comparison grid of blogging software:
the
Blog Software Breakdown on asymptomatic.net, which is useful but mostly based in 2004.
Even better than that, I found
the weblogmatrix site.
It's interesting to look through these and see what the range of features are. I wanted to have something that's free, and that I can separate out categories of posts, so that people who are just interested in our cats and our personal life don't have to read long detailed posts about carburetors or computers or electronics, or vice versa. I discovered there are web tools that aren't database-based, and some that are based on php rather than on perl (I like php and all my old web site stuff is written in it).
I ran across blogging software that I'm going to check out, called "
Pivot". It's a dynamic site too. It stores data in flat files and is based on php. It has categorization for blogging, and hooks for photo uploading. And it imports from blogger. So I'm going to try it out. Don't know when. We shall see.
I'm glad I took the time over break to do this transition, when I can concentrate on it and get things right the first time.
That's all from here. I hope everyone is having a good holiday!
Labels: craigsteffen.net
Monday 21 December 2009 at 01:54 am
New...and yet just the same as before...just with a new IP address.
Test post.
Labels: blogtest
Saturday 19 December 2009 at 4:02 pm
Ok, last post from the old hosting company. Restarting DNS propogation. See you on the other side at the new hosting provider,
vps.net.
Labels: craigsteffen.net
Saturday 19 December 2009 at 2:12 pm
no packages today. No toys yet. Bother.
Labels: christmas
Saturday 19 December 2009 at 1:56 pm
Ok, I've begun making the changes that will move craigsteffen.net over to a new host. Most of the changes are straightforward; however, the first change, which shouldn't have operation changed anything, caused blogger to not be able to ftp to my web site, so I couldn't make a blog post.
The old setup is fraught with problems, the new setup is simple and straightforward, so really I don't care why the hybrid setup doesn't work. At this point I'm going to proceed ahead full steam and sort out the new setup once DNS has propogated.
WHAT THAT MEANS: It's likely that this will be the last blog post I make with craigsteffen.net at its current host, since apparently I doesn't work mid-transition. SO...there will most likely be no posts here until everything has propogated, which will take a day or two. Tune back in on Monday or Tuesday and everything should be fine.
For updates in the mean time, just look at the right side bar at my twitter feed. , or directly at
my twitter update page. I'll post news there.
Wish me luck!
Labels: craigsteffen.net
Saturday 19 December 2009 at 12:59 pm
I bought the domain craigsteffen.net when I saw
Wil Wheaton had wilwheaton.net. A lot of the site has remain unchanged since that time, although I've certainly added content.
I really outgrew my old hosting site a couple of years ago, but I've failed to make the move until now. I just changed the DNS authority definition of craigsteffen.net. If I did it right, nothing as far as how the web site looks will change at all for the moment. If I screwed it up, then the site will disappear for a couple of days.
Anyway, for like the 7 people who read this blog, hopefully the next week will be slightly interesting.
The hope is that over the next weeks and months I'll able to set up stuff on my web site that I've been wanting to do for years.
So stay tuned.
Labels: craigsteffen.net
Sunday 13 December 2009 at 8:34 pm
Am I missing something? What statistical wisdom is it that I'm missing?
A pre-made video package on the NBC pre-game show for tonights game laid it out, and the answer pretty much was that if you rest your players for the past few games of the season, you lose your first game of the playoffs. If you play through the end of the season, you do well in the playoffs.
The Tony Dungee (former Colts coach and now a commentator) and the head of the Colts organization (via satellite link) both said that "oh yes, you need to not play the starters so that they don't get hurt".
WTF? Did they watch the video bit? Did they watch the same games I did for the last four seasons? If you leave your starters mostly out of the games for a month, they GET RUSTY and PLAY BADLY and LOSE their first playoff game. Why is that so damned hard to understand?
I really don't care about a 16-0 record...well, not THAT much. But really, I'm getting sick of the Colts playing really well, resting their starters until their first playoff game, and then getting wacked because some desperate team who's been playing hard for the last month takes them out of the playoffs because they want the game worse.
Argh. I hope that's not the effective end of the season.
Labels: colts
Thursday 03 December 2009 at 8:32 pm
[Sorry; had work stuff and then Thanksgiving travel and now I'm finishing up a paper. Busy. Hopefully blogging more now.]
The
Ares I-X rocket prototype team had their 30-day post-launch briefing today. Apparently they're mostly just getting the raw data reconstructed. The basic status is that the launch went very well. They have telemetry data for most of the flight. The status report from the meeting is linked from
the Ares I-X status page on nasa.gov.
The briefing wasn't on NASA TV, but it was streamed live on the internet. The team will have 60 and 90 days post-launch briefings as well. If you're into that sort of thing, you can keep track of it via the
Ares I-X twitter account.
Labels: ares, nasa
