lukemiller.org

The Open Wave Height Logger (OWHL) project has reached another minor milestone with the release of a new hardware revision, RevC.

This is a redesign of the three printed circuit boards, breaking physical compatibility with the older revisions, but it maintains software compatibility with the existing OWHL code (hardware designs and code available at the GitHub repository: https://github.com/millerlp/OWHL). The goal was to make the hardware a bit easier to assemble, and make certain parts (the micro SD card) easier to reach. All of the tiny surface mount components, save a few, are now on a single side of each … Continue Reading

GetFileAttributesEx D:\Arduino\libraries\SdFat/SdInfo.h
D:\Arduino\libraries\SdFat/SdSpi.h: The filename, directory name,
or volume label syntax is incorrect.
The error message above started cropping up shortly after I upgraded to Arduino 1.6.8 on Windows 7 x64. The cause seems to be due to some folder becoming locked in the Arduino compile pathway. One solution seems to be to close the Arduino software, restart it, and attempt to compile again. The program will compile ONCE, and then lock up and fail on a second compile attempt.

This Arduino forum thread recounts the same error: https://forum.arduino.cc/index.php?topic=366757.0

Another workaround seems to be switching the board … Continue Reading

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.

Assembled prototype housing

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

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

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 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

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