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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

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