Disassembling an ancient Si-Tech dry suit exhaust valve

Experienced cold water scuba divers will tell you that a dry suit is a vital piece of safety equipment, especially in challenging conditions (seriously, they’ll tell you without prompting, and then babble on about their gear until you walk away). Serious divers will also tell you that maintaining your gear in tip-top shape is an important safety issue, and all service should be done by trained technicians (again, it’s like that old joke: How do you know someone is vegan/went to Princeton/is from California? Answer: They’ll tell you. Divers, particularly overweight men with walrus mustaches, are the same way when … Continue Reading

Open Wave Height Logger prototype in the water

I finally got around to deploying a prototype OWHL unit in the real live ocean to log some waves.

The low-tech housing is made of 1.5″ schedule 40 pvc pipe. The pipe snugly fits the D-cell battery holder, while the electronics fit inside the modified 1.5″ end cap.

Components of the housing.

Components of the housing.

Prototype housing

Assembled prototype housing

I try not to rely solely on the tapered threads of the … Continue Reading

OWHL micro SD card current draw tests

As outlined in an earlier post, I found that certain old micro SD cards were performing spectacularly poorly when it came to power consumption because they failed to go into a low-power sleep state immediately after writing data to the card. I recently purchased a few new SanDisk micro SD cards in various capacities to see how they behaved. I purchased 4GB, 8GB, 16GB, and 32GB SanDisk cards from Amazon in November 2014. These were all tagged as “Ships from and sold by Amazon.com” and ranged from $5.99 to $12.99.

The good news is that all 4 cards behaved properly … Continue Reading

Extracting NOAA sea surface temperatures with ncdf4

I’ve written previously about some example R scripts I created to extract sea surface temperature data from NOAA’s Optimum Interpolated Sea Surface Temperature products. If you want daily global sea surface temperatures on a 0.25×0.25° grid, they gather those into 1-year files available at http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.oisst.v2.highres.html. If you want weekly average SST values on a 1×1° grid, you can get those back to 1981 at http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.oisst.v2.html. If you just want a smaller file for a single day on the 0.25×0.25° grid, you can find those at http://www.ncdc.noaa.gov/sst/griddata.php.

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Revised Open Wave Height Logger battery tests

The Open Wave Height Logger is meant to be a submersible pressure logger that will record absolute pressure at 4Hz for several months to give a record of wave height, and ideally do this on a single set of 3 D-cell batteries. I have recently made a few changes to the OWHL software, and discovered a major flaw in my original battery test. As a result, I have begun a new round of battery tests. The hardware and software changes are described here, and new battery test results are shown at the bottom of the page.

I was … Continue Reading

The effect of water temperature on whelk drilling speed

Last year I published a little paper showing how whelks (Nucella lapillus) drill through mussel shells at different rates depending on water temperature. This involved making hundreds of hours of recordings of whelks slowly scraping their way through the calcium carbonate shell of Mytilus edulis mussels in different water temperatures. The video above includes two examples of those recordings from two different snails of the same size, highlighted as red dots on the graph in the video, one taken at a water temperature of 9°C (48°F) and the second at 17.5°C (63.5°F). What you’ll notice … Continue Reading

ffmpeg time lapse notes

ffmpeg is a movie-encoding command line tool that is also useful for capturing and assembling time lapse movies, particularly using webcams. Below are some example commands to get it to do stuff. It is run from a terminal command line on Linux, OSX, and Windows. You will probably want to add the location of the ffmpeg files to your system PATH so that you can invoke ffmpeg from any directory.

The code shown here is specific to Windows 7 and later machines, so some commands will not work on OSX or Linux. Specifically, Windows uses the “dshow” option for … Continue Reading

Early Open Wave Height Logger battery tests

The Open Wave Height Logger prototype stack.

The Open Wave Height Logger prototype stack.

Following on the previous post about the Open Wave Height Logger project, I’ve been conducting a simple battery life test. One of the prototype OWHLs was powered by a 3 D-cell alkaline battery pack and shoved in the freezer for 32 days. The image below shows the collated daily data files for that time period, during which the data logger was sampling 4 times per second continuously. The black line is pressure in millibar, … Continue Reading

Open Wave Height Logger

OWHL – The Open Wave Height Logger
OWHL is a project originally dreamed up by Jarrett Byrnes and Ted Lyman at UMass Boston. Early on they contacted me for my thoughts on how to accomplish the goal of making a cheap, long-life pressure sensor data logger that could be used to record ocean wave heights near shore. I joined the effort during the initial specification stages. Ideally this device could be mounted on the seafloor at ~10 meters depth offshore, and record surface waves at 4 Hz for many months, with data saved to a micro SD card in a … Continue Reading

Lizards

Smug looking lizards.

Papoose_narrows_lizard_13

Midday, 100mm f/8

Papoose_narrows_lizard_16

100mm f/8

They seem awfully contented.

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