Sunday, 22 April 2012

Crunch Time

We're getting close to our in water deadline of April 28th and here is another update.  Our motors have finally arrived after bouncing around Florida, Texas, Quebec, Texas again, Nova Scotia and finally to us!
Motors Arrive
They are shiny aren't they.  They will go into our new actuator design which is completely waterproof, capable of up to 3 Nm and around 60 RPM.  Our test actuator has just finished being assembled and tested and the rest are being machined right now by Engineering Techinical Services, which has generously donated the machining time.  Thanks Tech Services!

In other news, the spreaders, shrouds and other rigging are nearing completion.  All of the pieces being attached to the mast this year are being placed on sleeves which fit over the mast.  This allows us to remove them for shipping, replace them if needed and keeps the structural aspects in tact.  The last pieces are being bagged right now.
Yes, that is a garbage bag and no that is not what we have been bagging with.  We use much more sophisticated milk bags from Tim Hortons. EconoBag from and mastic tape helps too.

Monday, 16 April 2012

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