Pinta is reborn

17/07/2010 at 8:18 pm | Posted in Uncategorized | Leave a comment
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We’ve started work on getting Pinta ready for the 2010 Microtransat. Having not done anything with her for over 2 years since we got back from the first WRSC in Austria we’ve finally started to get something done. There’s a few changes and improvements.

  1. We now have a “standard” robot control board for all our robots (boats and several wheeled vehicles). This includes a PIC18F4550 microcontroller, a Gumstix, 8 relays and serial port connectors. Of course standard is a bit of a strong word as we’ve already soldered a load of extra cables onto Pinta’s board to cover situations that we had envisaged when we designed it.
  2. The compass has been changed for a simpler and cheaper Deventech CMPS09. This operates in PWM mode and lets us use the PIC to read the compass, freeing up a serial port on the Gumstix that we can use for the Iridium modem. The real reason is because the compass got stolen for another boat!
  3. We now have a proper Sirf3 GPS (a USGlobalSat EM-408) instead of using Telit GM862-GPS units or Garmin eTrex’s.
  4. The GPIO14 I/O extender which we used to control the tiller pilot is now gone. Instead we do everything directly from the PIC and talk to the PIC over a serial line.
  5. We used to use a hall effect sensor and a magnet embedded in the drum which winds the main sheet to count the number of turns we’d made of the main sheet. This has now been replaced by a 10 turn potentiometer mounted below the sail motor. This gives a more reliable absolute position rather than just relative positions which rely on everything being started from a sensible position.
  6. The software control system is now based on the control system used in our miniature MOOP boats which is an evolution of the original Pinta control system only with lots more testing (50+ sailing days), several new features and lots of bug fixes.
  7. We’re adding a backup tracking unit based on a SPOT satellite tracker. This is a self contained unit running on a load of AA lithium batteries. All SPOT can do is send three types of message: Ok, help and 911. Ok just sends a predefined message with your location to some predefined contacts. Help sends a different predefined message to another list of contacts. 911 contacts some rescue coordination centre who will liaise with local search and rescue to find you. We’ve just setup a microcontroller to push the Ok button every 6 hours. This is in its own self contained box so even if everything else in the boat fails this should still alert us of the boat’s location.

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