"If you can't fix it with a hammer, you've got an electrical problem"

Well it looks like we've got an electrical problem then.  After a long spell of debugging communication issues between the Arduino and the BeagleBone, we had run into another challenge: the GPS.
Pictured above the team has taken the Arctica (the boat) and her sensors outdoors to see if we can get a fix with the GPS.  The GPS is the eyes of Arctica and without it  she would loose all sense of purpose in her life. At the time we couldn't get the GPS to pick up any satellites and thus couldn't get a fix. Either the GPS itself (hardware) or somewhere within the many lines of code that Daniel has hand crafted (software), something wasn't working.

After some background research on the GPS and how it works, along with a new GPS, we managed to get a proper fix.  However nothing is ever easy and we are now faced with the task of sending the way points from the Arduino to the BeagleBone for course plotting.  This involves setting up the "mailing procedure" of the data. This procedure lets the BeagleBone know what it should be receiving (GPS coordinates) and tells it not to sign for the parcel if it thinks it's getting garbage data.

Guess we'll be giving the hammer a rest for a bit. Although some days I'm sure Dan feels that a little persuasion here and there wouldn't hurt.

Shorts! and not because its summer.

So it's finally may in St. John's and to say hello it snowed all day.  Lovely slushy stuff. So no wearing shorts.

However, we have other shorts.  The electrical kind.  Luckily our power supply is smart and decides to not turn on when there is a dead short. So for future reference, all you board designers who think you are clever and add power and ground planes on the top and bottom of your boards.  Use nylon stand-offs or at least leave enough room that the aluminum doesn't cut through the solder mask and make your board think it should be summer time.

Electronics Box

One of our problems last year was our power connections from the batteries to the everything else got wet and shorted.  There was lots of green corrosion and needless to say a complete lack of power to do other things, like drive motors.

This year we are moving our batteries inside a waterproof (IP67+) box along with the electronics.  All of the connections are made through circular connectors which have sealing glands around the wires and face seals.  They're also made of plastic and quite light.

Electrical box with circular connectors installed and motor driver board in place

We had a setback a few weeks ago when after working on getting the wiring set up all of the connectors were left in a box along with the heat gun and heat shrink.  Unfortunately, the resident lab thief decided the heat gun would be lovely in his personal collection (no joke).  All of our connectors were stolen.  A quick call to Tyco Electronics, however, and they agreed to send us replacements.  Thanks TE!

Another change this year has been to change the communication from the main controller to the motor controllers to I2C.  This change allows for easy expansion.  If we ever needed more motors we just add another board to the stack.  Right now we can control 4 motors using PID loops with quadrature feedback.  The motor drivers are rated to 12A without heatsinks and can operate up to 16V (we run at 12V).  There are two Arduino pro minis on the board and each one is responsible for two motors. This division allows you to actually expand the system two motors at a time.  The motor controllers provide current feedback which we use to limit the torque output (so we don't break the boat when something jams).  The best part is that all the code is updated too and it works.  Check out the repo here.

Stay tuned for more updates as we ramp up this week getting ready for first sea trials as the ice is off the lakes now!

Yeah, It's a tight fit

Electronics Rev2

We've recently put together our new electronics package.  It is essentially a breakout board for all of the different off the shelf boards we use. Check it out!  It has a Seeedstudio Arduino Mega as the master controller, a 3.5A 5V switching regulator from Pololu, SD Card data logging, 4x 12A motor controllers.  The motor controllers are controlled by two Arduino Pro Mini's (2 motor controllers to each mini) which take quadrature encoder signals as feedback for motor position and current feedback for torque limiting and control.  Big improvement over our previous protoboard ratsnest.

Our second generation wind sensor is almost put together as well.  It uses a AS5040 magnetic encoder chip.  So far the whole thing weighs less than 15g. (ignore the mastic tape I needed something to hold the vane on temporarily)  It outputs a pulse at 1kHz equal with the width equal to the orientation of the magnet attached to the wind vane shaft.