Friday, June 27, 2008

Belated Mirror Squeezer Results

I did one "live" run of data collection from the parabolic mirror squeezer, but after I did it I realized there was a major problem. The pipe was much longer than the mirror width, so it overhung. Too late, I realized that this meant there was unheated oil in there, making the temperature measurement invalid. And I don't even know what direction the error was worse in, since the overhang could also act as cooling fins. Anyway, here's the graph of the results:

It looks very similar to the original run in a hotbox:

One major difference: Check the x-axis. The parabola run is at least 4x steeper.

Anyway, if I get some sun this weekend I should be able to re-run with more accurate results.

Tuesday, June 17, 2008


  • The diet hit a plateau. I'm down by 43 lbs from when I started, but in the last 30 days it's only changed by .5 lb. Looking at the chart from a year ago, I think I see a pattern. It was going down very slowly in May/June 2007, too. Looks like maybe 3 lbs in 60 days.

    There's probably two things going on. First, every year I imagine early summer weight loss should be easy. "Winter hibernation pounds just melt away naturally!" Second, a lot of good, fresh food shows up at the store.

  • I used to listen to Pandora at work. The advertised feature, discovery and laser(ish) targetting of your tastes, worked great. The problem was that the selection wasn't so great. I was down to about 30 songs that they just endlessly looped for me. Then I switched to The targetting isn't very good, but the selection is pretty huge. Exhibit A probably says more about how out of the loop I am for just now finding this, but still: Pretty hilarious (Lyrics)

  • And speaking of nerds: Do you like math? Do you also like mechanical devices? Then you will probably love How Round Is Your Circle. It's filled with mechanical ways to make, or approximate, mathematical functions, such as for linkages. The main problem with the book is that it's too short. It should really be a set of volumes so he can better explain each item. (Video teasers).

  • I have dismantled and cannibalized the Squeezer for a much simpler version of a parabolic trough now in production. Stay tuned!

Friday, June 6, 2008

Speaking Of Things That Don't Work

My house is crammed with computers, but only two of them (mine and Mrs Username's) are connected to the internet. Which means the kids always want to use them to play games.

The basement is wired, so last night I finally got around to hooking one up. It's got some version of Windows on there and already has a network card, so it should be easy, right? Drivers?? I don't even know what the card is! Not to mention the fact that I'm not too comfortable putting a Windows machine on the internet.

Then I get a crazy idea: I'll make it dual boot Ubuntu1! Takes me 45 minutes to download the latest disc, i.e. less time than it would have to identify, locate, download and install a NIC driver. Completely easy to install: Other than the fact that I had to adjust a slider to say how much room to leave for the existing Windows partition, I didn't have to tell it anything at all. It even got on the internet all by itself to download updates.

The question is: Is making my kids dual boot into Linux to play games child abuse or child undangerment? Either way, it certainly builds character.

1Actually, Xubuntu, because this is an older machine. I considered Edubuntu, but I think I'll go with the small, fast one and then add kid-oriented packages.

Monday, June 2, 2008

Things That Don't Work vs Things That Do

I've never been completely happy with my temperature logger. It's a bit fragile in the sense that if anything at all goes wrong, and there's no way to tell that at the time, I lose the entire run. I lost a run Memorial Day weekend.

Instead of storing the measurements on the Arduino, I'd like to instantly beam them onto my computer far inside the safety of the house. That way I can track things realtime as well as be assured that I have them. Coincidentally, for my birthday, I got both another Arduino1 and Making Things Talk.

The book describes a great number of schemes to make microcontrollers talk to each other and to computers. You can use wireless networking, bluetooth, XBee, etc (I have only the vaguest notion what some of these are). Naturally the easiest protocols require the most expensive hardware. I only need one way, slow communication, so I got a simple RF module.


It works just like a serial port! Just connect the transmitter to the TX pin and the receiver to the RX pin! It Just Works(tm)!



Perhaps my unit was faulty. I found many tutorials and guides across the internets and while results varies, I can't ever really say it worked. I did see data appear for a short time, but mainly what I saw was noise. Or nothing at all, which is even less explicable.

Last night I had a brainwave. Or brainstorm. Something happened to my brain and it resulted in an idea. Why not use a wireless laptop as the go between? The kids have these OLPC dealies. The laptop has a USB port and does WiFi. I have a WiFi router (specifically purchased, used, to work with these laptops). About 30 minutes and 10 lines of Python later, I was reading values from /dev/ttyUSB0 and sending them out over a socket to my desktop to another 15 minutes and 20 lines of Python.

The guts of the entire scheme are already there. But with so much success so fast, I'd like to add features. For instance, instant graphing of values on both ends. A protocol so that the laptop knows if there's been an error and can tell me, out in the field. When I have more than one sensor, I'll need a way to indicate which sensor had what value. It'll be like a complete Science Sensing Station!

1If you are at all interested in robots, sensors, controlling stuff with computers, electronics or just plain messing around, I highly recommend the Arduino. That SparkFun item is all you need, assuming you have a USB port (and possibly a cable). may also need some external electronics, depending on what you want to do. LEDs, resistors, motors, etc.