Friday, August 30, 2019

Autonomous Raspberry Pi

Solar powered, with a wireless keyboard and touchpad.

Solar powered, with a wireless keyboard and touchpad.

The solar panel

Closed. The keyboard can also fit in the box.

Sunday, April 21, 2019

San Juan Islands, WA

Data logging in San Juan Islands, Washington:

Apr 19-21, San Juan Island

Apr 22, San Juan Island to Orcas Island

Apr 23, Hiking in Orcas Island

Apr 24, Hiking in Orcas Island, Mountain Lake

Apr-25, Back ashore

Data logging was done as explained here, here and here.

Tuesday, March 12, 2019

Easy Low Pass Filter

Instead of implementing a buffer and smooth it, there is a much easier and efficient way to do it. Here is a simple JavaScript implementation. First you define your accumulator function:
 function lowPass(alpha, value, acc) {
   return (value * alpha) + (acc * (1 - alpha));
Then you need to define your APLHA coefficient:
 const ALPHA = 0.015;
Then you can invoke the accumulator with the aplha coefficient on the data to smooth:
 let filteredGustArray = [];
 let acc = 0; => {
   acc = lowPass(ALPHA, dp.gust, acc);
This produces an array containing the smoothed data. Here is a representation of what it looks like, along with the data to smooth (raw data in red, smoothed data in blue):
The demo data are available here. Just run the script with nodejs like
 $ node max.gust.js both > data.csv
This will produce a csv file you can then import into any spreadsheet program, to see the figure above.

Monday, March 11, 2019

Smart TCP Watch, prototype.

TCP, no BlueTooth (and as a result, no Smart Phone) is required. The "watch" can connect directly to the network.
See a first prototype here.
And a short video here.