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Control a Tiller Autopilot with a Raspberry Pi.
INDEX - Introduction, Parts.
 

This Tech Tip expands on Tech Tip E12, "Install an Electric Autopilot" to describe the electronic control hardware for steering an SJ23 by the wind.  The intent here is to describe this installation with sufficient detail to fabricate and configure the electronics yourself.  I can foresee a new winter project with this!  Stay tuned for updates.

A Raspberry Pi and associated hardware is probably the best option to steer an SJ23 by the wind since it is next to impossible to mount a mechanical wind vane on the narrow transom.  It is quicker to enable or disable the electronic vane than a mechanical one.  Compared to a full manufacturer installation, the Raspberry Pi and associated hardware is likely the least expensive system to control a Tiller Pilot.  It consumes very little power which should be dear to the hearts of many SJ23 sailors whose boats have little or no battery charging capability.  While it is feasible to operate the electronics on just a deep cycle battery, it is best to install a battery charging system as well.  See Tech Tips E07, E04, & E01. 

Use a RASPBERRY Pi to Steer an SJ23 to the Wind.

"I installed this electronic hardware onboard my SJ23 so it can sail by the wind.  There is also a chart plotter and a lot of other functions too numerous to mention.  With the autopilot functioning I can concentrate on sail trim or do whatever else I need to do onboard.  The system makes smaller corrections than a person can, and more often.  Two advantages of this system are much lower cost than a full manufacturer package and low power drain.  I have yet to install a battery charging system since the electronics draws very little power and so far my charged battery can handle my daily floats.  Notice the Raymarine vane at the masthead.  That's where it all starts.  For a video go to https://youtu.be/3zMjUs2X3qU."    Jim Dalessandro.

Why pink sails?  Email Jim for that answer.  He says, "I love the pink reflection off the water.  Everything on deck has a pink hue as well.  Its like wearing rose coloured glasses."

PARTS LIST for VANE STEERING:

I think these are all components required for the vane steering function.  This list may change.

• RASPBERRY Pi (4) Model B - This microprocessor circuit board has four USB ports (data), one RJ45 (Ethernet) jack, & one HDMI (video & audio) jack.  It also needs a good 32GB micro SD card plugged in the jack (works like a hard drive) and requires "Bareboat Necessities (BBN)" operating system installed.  BBN is a free Linux OS that allows connected devices to talk to each other. 

• INERTIAL MEASUREMENT UNIT (IMU) - Measures and reports a body's specific force and angular rate using a combination of accelerometers, a gyroscope and sometimes a magnetometer.  This circuit board measures 9 axis motion; pitch, jaw, roll, acceleration, etc.  The board is plugged into the 40 pin connector on the Raspberry Pi.  Once installed on the boat it must be calibrated to do its job correctly. 
  - If you buy the IMU from pypilot.org the unit is tested and includes wiring to connect to the motor controller.

• PyPilot  MOTOR CONTROLLER - This circuit board, with "Tiny Pilot" software installed, drives the Tiller Pilot (brushed) motor directly with up to 8A of current.  It has an alarm threshold that can be programmed to detect when the Tiller Pilot draws too much current, IE: end of travel.  Other settings can also be configured. 
  - Buy from pypilot.org.

• PROJECT BOX - A protective housing for the Raspberry Pi, IMU & PyPilot circuit boards.  Available in many sizes with screw on lid.
  - Buy from electronics retailer or home renovation electrical dept.

• 5V POWER - The Raspberry Pi, IMU & Motor Controller operate on 5V.  A 12V to 5V DC/DC 10A converter is required. Operate it from the same 12V power source as the Tiller Pilot so all is switched on/off with a single switch. 
  - Buy from electronics retailer or make one using a series regulator chip.

• RAYMARINE st60 WIND VANE - Used to measure wind speed and angle.  Sends data using NMEA commands.  Comes with 30M long cable.  It is usually installed at the top of the mast but may also be installed on top of a mast installed at the transom.  I have a feeling that any wind vane that transmits NMEA data can do this job.  Requires a RS485/USB adapter to send data to Raspberry Pi USB port.  Also sends power from Pi USB port up to vane.

• TILLER PILOT - Installed in the cockpit to push/pull the tiller to steer the boat.  A Raymarine Tiller Pilot can be controlled by NMEA commands or by external DC power connected directly to the motor.  For the DC power the internal sensors and electronics must be disconnected (bypassed) and the 2 wires from the motor controller connected directly to the Tiller Pilot motor.  The motor controller can then send voltage directly to the Tiller Pilot to make course adjustments.
  - It might be desirable to install a water proof slide switch that switches the Tiller Pilot motor input from the internal electronics to the external PyPilot Motor Controller.

ADDITIONAL PARTS for CHART PLOTTER:

I think these are the additional components required for the chart plotter and other functions.  This list may change.

• AIRMAR DST810 MULTI-SENSOR - Installed through the hull to measure boat speed, water depth and temperature.  Almost all hull transducers are manufactured by Airmar and relabelled by the retailer.

• SEYAK ST1 to NMEA Bridge - Converts Raymarine ST1 commands to NMEA data so instruments & transducers can talk to Raspberry Pi).  Plugs into Raspberry Pi via USB cable.  There is also a WI-FI version.

• RAYMARINE st60 DISPLAY - Installed on the cockpit bulkhead for ease of control while sailing.

• A SMALL TOUCH SCREEN - For chart plotter function.  Use the official 7" Pi Screen.  It controls everything, not just chart plotter.  You can also run the system with a phone or tablet instead of a screen. This is another way to reduce electrical consumption. 

• GPS PUCK - They were originally installed on the transom for an unobstructed view of the sky to receive signals from the satellites.  Today many can be installed in the cabin to operate with good performance.  It measures coordinates, boat speed, and altitude.

• ROUTER - Optional, to connect to the marina Internet via WI-FI.

The first objective is to assemble the components on a work bench and get them working. 

The second objective is where to install this hardware on your SJ23.  It has to be convenient to use.
 

The following is reference info to use during this construction, Tech Tip E12.

ELECTRICAL WIRING - The Raymarine ST1000+ or ST2000+ Tiller Pilots are capable of being controlled by an external NMEA 0183 compatible device (GPS navigation receiver, plotter, etc) so it can follow a programmed route over the ground.  This is superior than using the, "hold this heading," switch when operating the boat through a cross current or cross wind.  To this end I installed a voice grade (Cat 3) wiring harness from the cockpit connector to the GPS.  The harness runs inside a cable tray along the top inside of the port locker, through the port cabin bulkhead (sealed with sealant), and across the cabin behind the companionway to a terminal strip below the VHF.  This where it is cross connected to the GPS to operate using NMEA sentences.  See Tech Tip E13 Instrument Interconnect, for further information.  The power leads continue on to the power breaker panel on starboard.

• NMEA - Data

• NMEA - Wikipedia, the free encyclopaedia

• Raymarine - ST1000Plus or ST2000Plus. (previously Autohelm).

• Simrad TP10 or TP20. (previously Navico).

• It is very doubtful that I will assemble this electronics in the near future.  I just don't have the time with all the other projects I have on the go.  So for further info, please email Jim Dalessandro.
   

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