PCB silkscreen sizes

Recently I’ve been getting my printed circuit boards manufactured through OSH Park, and they make good quality (to my eye) boards at a decent price, with less than a 2-week turnaround time. They also take files directly from Eagle software, rather than having to produce gerber files (though this is also an option).

On a recent set of orders I played around with the silkscreen label sizing in my copy of Eagle 7.2. The OSH Park guidelines say that their minimum silkscreen line thickness is 5 mils (0.005 inches). This is the thickness of the lines that make up … Continue Reading

iButton internals

I’ve written in the past about iButtons and my attempts to waterproof them. Although iButton temperature dataloggers are fairly well sealed, they are not waterproof. But if you know an old person that used iButtons in the late 90s or early 2000s, they might claim that iButtons are absolutely waterproof.

It turns out that iButtons are one of those rare things in life that really were better when you were a kid. In the old days they could be put out in the ocean for weeks or months, completely bare, and most of them would survive just fine … Continue Reading

Basic text string functions in R

To get the length of a text string (i.e. the number of characters in the string):


Using length() would just give you the length of the vector containing the string, which will be 1 if the string is just a single string.

To get the position of a regular expression match(es) in a text string x:

pos = regexpr('pattern', x) # Returns position of 1st match in a string
pos = gregexpr('pattern', x) # Returns positions of every match in a string

To get the position of a regular expression match in a vector x of text strings … Continue Reading

Electronics parts list

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


That’s all there is to it.

Preserving equations in Powerpoint when going cross-platform

This is another one of those tricks that I forget how to do unless I write it down. When I move Powerpoint (2010) presentations from my Windows machine to my Mac (Powerpoint 2011), the equations usually get destroyed along the way. The workaround is to turn the equations into images that can’t be altered by the Mac.

For example, here I’ve got an equation plopped into a blank presentation, with the equation editor toolbar.

The equation.

The equation.

The first step is to copy the entire equation and the text box … Continue Reading

A plot of co-authorships in my little corner of science

author year count image

Here’s a mostly useless visualization of the collection of journal articles that sits in my reference database in Endnote. I deal mostly in marine biology, physiology, biomechanics, and climate change papers, with a few molecular/genetics papers thrown in here and there. The database has 3325 entries, 2 of which have ambiguous publication years and aren’t represented above. This is by no means an exhaustive survey of the literature in my field, it’s just an exhaustive survey of the literature on my computer.

To make this figure, I first had Endnote export the database to … Continue Reading

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.

Continue Reading

Page 3 of 1112345...10...Last »