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Solve ST2000 fluxgate compass problem using PyPilot?
#1
Hi folks,

First time poster here. Great to find this community.

I'm looking for some advice regarding my ST2000 and the poor performance of the device going downwind with substantial quartering seas on the stern. What I observed is that as the wave begins to overtake the sailboat and lift the stern, the AP initially steers in the wrong direction, sometimes going all the way over, even though the boat heading was not yet affected much. Then, as the wave starts to yaw the stern, now the AP reacts by pushing the tiller over in the other direction (the correct direction). Under the right (wrong?) conditions the boat sometimes will then round up into the wind, which of course is not good. My suspicion is that the compass is being adversely affected by the pitch of the boat (stern getting lifted by the wave) so that it thinks there is a change in heading when actually there is none.

To address this, what I think I might like to do, is replace the compass with an external IMU/controller, possibly using the PyPilot.

The questions I have been so far unable to answer definitively:

Can I use the ST2000 as just a dumb actuator, and control it from a device like the TinyPilot?

  https://pypilot.org/store/index.php?rt=p...ry&path=71

Can the TinyPilot control the ST2000 such that heading information is taken from the IMU and used to steer the boat?

Do the ST2000 and PyPilot support the necessary NMEA 0183 sentences? What sentences would be used for this purpose?

Thanks for any comment.
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#2
(2020-10-15, 04:11 PM)madhatter101 Wrote: Hi folks,

First time poster here. Great to find this community.

I'm looking for some advice regarding my ST2000 and the poor performance of the device going downwind with substantial quartering seas on the stern. What I observed is that as the wave begins to overtake the sailboat and lift the stern, the AP initially steers in the wrong direction, sometimes going all the way over, even though the boat heading was not yet affected much. Then, as the wave starts to yaw the stern, now the AP reacts by pushing the tiller over in the other direction (the correct direction). Under the right (wrong?) conditions the boat sometimes will then round up into the wind, which of course is not good. My suspicion is that the compass is being adversely affected by the pitch of the boat (stern getting lifted by the wave) so that it thinks there is a change in heading when actually there is none.

To address this, what I think I might like to do, is replace the compass with an external IMU/controller, possibly using the PyPilot.

The questions I have been so far unable to answer definitively:

Can I use the ST2000 as just a dumb actuator, and control it from a device like the TinyPilot?

  https://pypilot.org/store/index.php?rt=p...ry&path=71

Can the TinyPilot control the ST2000 such that heading information is taken from the IMU and used to steer the boat?

Do the ST2000 and PyPilot support the necessary NMEA 0183 sentences? What sentences would be used for this purpose?

Thanks for any comment.

I am also going to do this.

The  ST2000 Motor will need to be wired to the Pypilot Controller. You will be able to use 2 of the wires in the raymarine wire harness, connector, and plug, the rest will be unused. Unless you want to use a limit switch.

I think the Pypilot supports NMEA 0183 for wind and waypoint data.
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#3
You cannot reuse the electronics of the st2000 unless you are really clever and can hack the circuit board.

The simplest way is to connect the dc motor directly to the pypilot motor controller.
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#4
(2020-10-20, 04:03 PM)seandepagnier Wrote: You cannot reuse the electronics of the st2000 unless you are really clever and can hack the circuit board.

The simplest way is to connect the dc motor directly to the pypilot motor controller.

@madhatter101, if you are looking to do everything yourself, you might be interested in seeing my bare bones build.  I drive a Autohelm 3000 motor (not ST3000).

  https://forum.openmarine.net/showthread.php?tid=2228

If you're looking to get something proven and supported, @seandepagnier's units might suit you.
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#5
There is a joystick mode in att least some of the autohelm pilots.
I have not found the seatalk command for this.

If the command is found you could theoretically driver the autohelm in joystick mode from THE pypilot.

This would greatly increase the user base as No hardware modifikation is necessary for old working autohelm systems.
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