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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

Here’s the start of a list of common bits and doo-dads I use for building electronics projects.

https://github.com/millerlp/parts_guide/blob/master/parts_guide.md

That’s all there is to it.

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.

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

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, and … 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

I have recently been developing a library for the Measurement Specialties MS5803 line of digital pressure sensors. These sensors are available in several different pressure ranges from 1 to 30 bar, they are submersible if installed in a proper housing, they communicate via I2C or SPI, and they cost around US$35. It’s fairly straightforward to interface the MS5803 with a microcontroller like the Arduino that can also communicate via the I2C or SPI protocols. They are a surface-mount style chip, meant to solder onto a 1.27mm pitch SOIC-8 layout (like the green board I used in the picture below).

[caption … Continue Reading