jeff's in town

Jeff Branson, the Gypsy Engineer from Sparkfun, has been evangelizing the masses with can-do spirit, sharp ideas, and mad skills. Here he his showing some kids how to use the new Sparkfun Data service for those of us who need a simple, effective, free place to post data.  This writer is already staying up late trying to run with some top-notch suggestions he has made.

In other news, I went to Walter Wood Hardware to pick up supplies for our first couple of buoys.

Happy Thanksgiving!

hangout with brian

Some of the crew did a video conference with Brian Huang of Sparkfun about using sleep functions to reduce power consumption in our projects. As usual, no matter the topic, Brian was on top of it.  The kids took down his suggestions.  He also gave some ideas on how to get the data coming over the Ethernet shield at the North Chickamauga site to graph, rather than just print some numbers on a blank IP address screen.
The key right now is to bypass the initialization "Press D12" part of the Vernier shield so that the probes take readings automatically once power has been restored to the shield following the sleep period (which would be most of the day).  If we're going to try to get by with using only a 20 ah battery in the buoy and come only once a month to check in for data harvesting and power check, we need to squeeze every milliamp we can.

charge controller still doing well

I've had the N3904 transistor in place of the BC548 and it seems to be fine. I think we're about ready to box one of these into a monitoring station.

charge controller tests out well so far

We've been testing a 6v charge controller schematic with a small 10w solar panel that students of mine built last year and a small 3 amp hour battery with an arduino attached as a dummy load. 

Here's the breadboarded circuit with battery.

And here's the schematic:

Thanks of course to electroschematics.com.

The LM 317 is a standard adjustable voltage regulator.  Output is regulated with the variable resistor.  Most lead-acid 6v batteries have 6.8 v as a cutoff voltage.   The reverse-biased zener diode 2D starts conducting when load reaches float charge and sends excess voltage to ground.
We've heat sunk the LM 317.  A 1W rated resistor for R3 is too low.  It gets way too hot for this application.  We substituted a a ceramic 10W rated resistor and it stays cool. We'll give it a few more days, and if performance still checks out, we'll solder a permanent circuit.  Some of our remote monitoring sites get at least mottled sunlight for a few milliamps each day.