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Marine Autopilot Project


My 42 ft sailing catamaran has an old old Robertson autopilot, which was high tech in its day but now there are only one or two people capable of repairing it.


My autopilot steering motor is a simple electric motor, driven by 12 vdc, simple relay output, one way for port and one way for stbd, includes an intregrated clutch which engages motor when autpilot is on. 


Required Inputs:


1.  Rudder position  -- operated by a mechanical arm at rudder post -- quantitative left, right, or center.  Ought to be some industrial  USB device that indicates rotation, or an arm driven potentiometer?


2.  USB GPS output --  current course in degrees.


Required Settings:  (software)


1.  Desired course


2.  Rudder response magnitude


3.  Rudder response speed/delay


4.  Rudder reverse response (meeting -- when turning to port, as rudder returns to center, it steers a bit to stbd first, then centers, to prevent ovcer steering.)


5.  Degrees and time for uncorrectable off-course alarm.


Required Outputs:


1.  Steering commands -- voltage to relays to operate steering motor -- stdbd & port. 


2.  Autopilot on -- engage steering motor signal (Note:  Steering motor has integrated clutch, which releases when autopilot switches off).  Power signal to relay to motor clutch.


2.  Total Failure alarm (relay driven, deadman switch, system failure drops input to relay, which failure sets off sonalert)


3.  Uncorrectable off-course alarm ( a software setting -- allowable degrees and time off course).




Considering attempting to integrate such a  RPI unit to OpenCPN [  http://opencpn.org/ocpn/  ]



I am on old web programmer, with a bit of various Basics and C++ .


Any suggestions or pointers would be appreciated.  I believe strongly in modifying other people's open source code.














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I would advise you to looking into the NMEA mutliplexer project. The best way to get information from your boat equipment and to send commands is by using the NMEA protocol. 




Good luck and keep us update on your progress. I want to get the NMEA data out of my boat into my Raspberry but didn't had time yet to work on this. 

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