30. May 2009 by Sean.

I spilled a beer on my laptop at last night’s working session.  Not just a little bit, either.  It was so bad that my off-switch stopped functioning and I had to yard my battery out before I started seeing sparks (wouldn’t be the first time my lair/R&D lab smelled of burnt plastic).  After that, I held my laptop keyboard under the tap, turned it upside down to let the water drip out, then opened it up as much as I could to let it dry out.  The next morning, it didn’t work very well.  It didn’t boot properly the first few times, I got USB-related blue screens of death, and the glide-point didn’t work. But, after letting it run, eventually all the moisture evaporated and it’s back to its usually crappy running mode.

 I don’t really know if that’s the proper procedure for a beer spillage, but I panicked.

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27. May 2009 by gmoney.

We are using 9 Pitsco “Ray Catcher” Solar Panel’s:

http://shop.pitsco.com/store/detail.aspx?ID=2550&bhcp=1

Each panel is rated at just over 3 watts (2.8 volts x 1,100mA), however our testing found each panel would output 3.0 to 3.25 volts in full sun (in February no less).   Preliminary sample circuit tests also showed that 2 panels in series were sufficent to charge up our 6V batteries.

The circuit we will assemble for the proto-boat tests will be 3 circuits with 2-panels in series and 1 circuit with 3-panels in series.  Those 4 circuits will then be connected in parallel.

There will be no diodes for 2 reasons: 1) we can’t afford the voltage drop, and 2) backwards current is unlikely to be substantial (i.e. it will be less than efficiency loss of a diode) and will not damage the panels themselves.

If anyone has a problem with mixing different voltage circuits in a parallel connection, or a problem with not using diodes — speak now or forever hold your peace.

Posted in Solar Power | 2 Comments »

8. May 2009 by Sean.

I really like that picture of me in the track pants and golf shirt below.  Very flattering. 

The eletronics guts are coming together.  Here is a 30,000 ft view of what’s happening:

The main board reads sensors from a number of sources - GPS module, compass sensor, light sensor, battery voltage sensor and temperature sensor.  It retrieves GPS coordinates from an eeprom and logs data to another eeprom.  In the off chance that we get our boat back after its big trip - we can see how hot it was, what the battery levels were, etc.

The main PIC microprocessor is programmed to calculate a target bearing from its current lat/long coordinates and the next lat/long coordinate.  It compares the target bearing to the compass (actual) bearing and then adjusts the motors using differential steering and pulse width.

The target bearing calculation is surprisingly tricky to do on a microprocessor.  Most of the issues are around precision when you’ve only got a maximum of 32 bits of precision and some complex calculations involving PI and arc-tangent.  Note how I use those terms like I know what they mean.  It’s all a ruse.

Thank goodness the fine people at HI-TECH have a C compiler which has trigonometric math functions and does floating point calculations.  Often when working with microprocessors, floating point calculations are a luxury.

The GPS module (home grown) offloads the work of parsing the GPS serial stream and serves it up as an I2C message to the main board.  Otherwise, this process alone would suck up about half of the microprocessor program and data space.

The Compass is a Devantech Magnetic Compass Module CMPS03

There is a real time clock chip on board to support the timed operations.  We would use the GPS time but we need to turn the GPS module off when it’s not being used.  That’s 50 milliamps we can’t afford.

Here’s what it looks like:

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8. May 2009 by gmoney.

http://www.findmespot.ca/en/

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7. May 2009 by gmoney.

http://www.ippnet.com/

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7. May 2009 by gmoney.

The support frame for the 9 solar panels is built from spruce plywood and is encased in 2 layers of fiberglass cloth.  Overlapping layers of fiberglass secure this frame to the hull’s wood ’skeleton’.   2 wooden frames are used as the bottom ’skeleton’ is used to support the return on the hull (keeping it stiff & sturdy), the top solar panel frame then  adds additional strength as well as provides an extended flat edge to secure the panels to.

Posted in Fiberglass construction | 3 Comments »

7. May 2009 by gmoney.

The construction of the transom on SolarCrawler was an epic journey of Engineering prowess.   A resilient transom is needed to handle the vigour of 400 total mAH of power pulsating through the electric motor shafts.

A double-walled transom is used because of the risk of water leakage.  The inner wall is constructed purely of fiberglass, the outer wall is spruce-plywood encased in multiple layers of fiberglass cloth.  Stress-tests will determine if fiberglass matt may be needed to provide additional support.

Posted in Fiberglass construction | 2 Comments »

4. May 2009 by Sean.

Here is a shot of the first boat design being float tested

Posted in Fiberglass construction | 2 Comments »