sat, 21-may-2011, 07:29
Back cabin, high water

Back cabin, high water

I started measuring the depth of Goldstream Creek a little over a year ago this week. Each morning I measure down from a particular spot on the bridge over the Creek to the top of the water or ice and report this (plus daily high and low temperature, precipitation, snowfall and snow depth) to the Weather Service. The following plot (if nothing shows up, click the following links to view a PNG or PDF version) shows the depth of the Creek at our swimming hole on the top, and the daily high and low temperatures on the bottom. The dark cyan line on the top plot is the height of the bridge (about six feet below the entrance to our house), and the dark cyan line on the lower plot is the freezing point.

At it’s highest, the Creek was just over two feet from the bottom of the bridge, the slough flooded into the dog yard about two thirds of the way across the lowest point, and the Creek seemed dangerously close to topping the banks. The photo at the top shows the back cabin during the high water event.

This year’s breakup was similar to last year: ground and meltwater from the surrounding area started flooding on top of the ice and over the course of a couple weeks, it eroded the ice below until the water level rapidly dropped to more normal summertime depths. One interesting note is that we seem to get a large pulse of water (the rise starting around March 11th) before the snow has started melting, which would seem to indicate that the first pulse is coming from groundwater sources. We don’t start getting afternoon temperatures above freezing until the beginning of April, and this is when snowmelt starts bringing the level up even higher.

When the level begins to drop, it’s pretty dramatic as we go from bankfull conditions to almost nothing in a week. This year we’ve still got wide shelves of ice hanging on the banks six feet above the level of the water.

The plot also shows the brief ice storm in late November where we got a couple inches of rain that froze on the roads and brought the Creek up slightly.

In the past, we’ve had more dramatic breakups where the initial springtime pulse of ground and meltwater breaks up all the ice in a couple days and sends it past our house crashing and grinding, but even the more gradual melting pattern of the last two years is impressive in how quickly the Creek rises and falls.

fri, 20-may-2011, 20:51
Fire from the back 5

We’ve got a pretty good view of the fire from behind the house.

And here’s one from a little later (10 PM). At this point it looks like the fire has burned out the hillside we can see and has moved off to the right.

Fire, 10 PM
fri, 20-may-2011, 18:43
Murphy Dome fire

The photo above was taken just before the intersection of Sheep Creek / Goldstream Roads and Murphy Dome Road, less than half a mile from where I work, and about four miles from our house as the crow flies. I’ve spent the last three hours backing up data, and getting our servers ready for possible evacuation. We’re both downwind (currently) and downhill from the fire, but it’s dangerously dry in Fairbanks right now, and if the wind shifts, we find ourselves evacuating our offices.

More as it happens…

sun, 15-may-2011, 11:25
Battery, Arduino, XBee

Battery, Arduino, XBee

Several years ago when I started messing around with Arduino and building my own weather station, I bought a few XBee radio chips with the idea of setting up some more remote sites without having to run wires out to the sensor stations. I spend several frustrating hours trying to get the radios to talk to each other, but couldn’t get them to work (I think this was because they were in API mode instead of AT mode). Then I got Building Wireless Sensor Networks and Arduino Cookbook and finally got everything working.

At the same time, the batteries in our UPS at work needed to be replaced, and rather than immediately recycling them, I took a couple home to see if they still had enough juice in them to work in a remote sensing capacity. They’re 12 volt lead-acid batteries (which may make them unsuitable for winter) that were rated for 5 Amp-hours when they were new. That should be plenty of power to drive an Arduino, XBee and a couple sensors. The XBee chips have some data pins on them, so I may be able to eliminate the Arduino from each sensor station, depending on the type of sensor I use.

The current setup, shown in the photo at the top, is designed to see how long a remote station can run on one of the batteries without any sensors and at springtime temperatures (typically between 20°F and 60°F at our house). The Arduino is reading the input voltage and sending it wirelessly to an XBee coordinator plugged into a SparkFun explorer board and connected to my small eeeBox computer.

Here’s the circuit diagram:

Circuit diagram

The analog input pins on the Arduino board are expecting voltages between 0 and 5 volts, so I’m using three resistors as a voltage divider to reduce the input voltage (nominally 12 volts, but potentially as high as 15V) to a range safe for the board. The sketch looks like this (almost identical to the sketch in the Arduino Cookbook except that the formula for resistorFactor is incorrect in the book):

const float referenceVolts = 5;

const float R1 = 2000; // A0 to V+
const float R2 = 1000; // A0 to GND

const float resistorFactor = 1023.0 * (R2/(R1 + R2));

const int batteryPin = 0; // A0

void setup() {
   Serial.begin(9600); // to XBee
}

void loop() {
   int val = analogRead(batteryPin);
   float volts =
     (val / resistorFactor) * referenceVolts * 10;
   Serial.println(volts);
   delay(1000);
}

Because the Arduino transmit pin (D1) is connected to the XBee receive pin (DIN) and the Arduino receive (D0) is connected to the XBee send (DOUT), anything the Arduino sends to the serial port is redirected to the XBee, which immediately transmits it wirelessly to the XBee receiver chip in the house.

At the moment, I’m only able to have the sender and receiver about 50 feet from each other before losing the signal, but I think that a pair of boards with whip antennas will work better than the chip antennas I’m currently using. I also set up my network such that the XBee Pro board (which has a supposed range of a mile) is the coordinator receiving messages, but I think it will work better as the sender. When the battery experiment is over, I’ll reverse the position of the XBee boards and see if I get better performance. I’d like to have a station out at the red cabin and potentially somewhere on the hillside, and for that to work the radios will need to be able to communicate over several hundred feet.

The circuit diagram was generated using circuit macros, which take circuit diagrams written in the m4 language and turn them into PIC files which are converted into LaTeX code using dpic. That sounds complicated (and it sort of is), but I much prefer describing the circuits in a text file than to trying to draw them using XCircuits or some other graphical tool. If you’re curious, you can download the code and a Makefile for generating the images.

Here’s what the data looks like so far:

Voltage over time

So far all I can see is a diurnal pattern associated with temperature: it was about 56°F at 6:30 PM last night when the data started, dropped to a minimum of 27°F at around 5:30 AM, and it’s been rising since, hitting 50°F at the end of the period shown on the plot.

fri, 06-may-2011, 09:07
Caslon playing

Caslon playing

This year Andrea got invited to speak at the Kachemak Bay Shorebird Festival. It would have been the sixth or seventh time we’ve been to the Festival, and it’s always a great time and a nice vacation for both of us. Because of all the dogs and cats, it’s hard for us to travel together, so most of our vacations are solo affairs while the other person takes care of the animals.

Unfortunately, as we were packing to leave, we discovered that our cat Caslon was sick with some form of feline lower urinary tract disease. That’s another way to say “a cat that can’t pee.” He got antibiotic and anti-inflammatory shots in the hopes that it’s an infection causing a bladder inflammation. We also need to keep him isolated so we can monitor what’s happening, and give him twice daily 100 ml subcutaneous fluid injections to hopefully keep things moving. As you can imagine, this isn’t the way I’d imagined spending the next four days.

The good news is I already took the time off from work, so it’ll give me a chance to catch up on some projects. The arctic entryway needs trim above the tile and around the windows and doors, and I’d like to build a more permanent setup for my standing desk at work.

And Andrea will have fun in Homer. We keep our database of animal observations on line, so I can track what she sees by looking at the 2011 Homer observations page.


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