Garmin reactor autopilot & Faria rudder indicator

[blampied]

Anyone know if and how I can link a Faria rudder indicator gauge
(about 24 years old, has only two wires coming to it, from the sender Red and Black)
to my Garmin Reactor autopilot. (Three wires red, black and yellow)

The Garmin autopilot is not currently connected to a rudder reference source. (It does work without a reference unit, but would be better with one)
Garmin make a rudder reference unit to fit it as an optional extra but it’s expensive and as I already have a Faria reference (that has been their since the boat was built 22 years ago) I’d like to try and use that.

 

[lpdsn]

From what I can tell with a quick web search or two, the Garmin Reactor Autopilot will output NMEA2000 (almost certainly PGN 127245).

The Faria rudder indicator looks like it is analogue.

So first of all, get a couple of pots and rig up a test circuit for the rudder indicator so you can determine how it works. Are you sure it is just two wires? The stuff on-line seems to indicate +ve, GND & Signal. Still with the pots you should be able to make the indicator move without risking blowing it.

Plan A could be to use a commercial product to convert the PGN to NMEA0183 RSA then say a Raspberry Pi and a DtoA circuit to get the right analogue signal.

There is a shareware version of N2K out there that probably supports rudder angle, so you could look at that with the DtoA circuit as a Plan B.

There are a number of forumites who've messed around with Pi & Ardunios that could offer some advice. AngusMcDoon used to do lots of bespoke circuits with microcontrollers but was prevented from continuing that on the forum.

 

[neil1967]

Why do you want/need to do this. I assume you have a Garmin controller and that will show you the rudder position? Or are you trying to use the Farina rudder position sensor to provide feedback to the garmin system?

 

[Blue Sunray]

From what I can tell with a quick web search or two, the Garmin Reactor Autopilot will output NMEA2000 (almost certainly PGN 127245).

The Faria rudder indicator looks like it is analogue.

So first of all, get a couple of pots and rig up a test circuit for the rudder indicator so you can determine how it works. Are you sure it is just two wires? The stuff on-line seems to indicate +ve, GND & Signal. Still with the pots you should be able to make the indicator move without risking blowing it.

Plan A could be to use a commercial product to convert the PGN to NMEA0183 RSA then say a Raspberry Pi and a DtoA circuit to get the right analogue signal.

There is a shareware version of N2K out there that probably supports rudder angle, so you could look at that with the DtoA circuit as a Plan B.

There are a number of forumites who've messed around with Pi & Ardunios that could offer some advice. AngusMcDoon used to do lots of bespoke circuits with microcontrollers but was prevented from continuing that on the forum.

Disregard the above.

The Garmin autopilot is not looking for an N2K feed, but a direct (and indeed analogue) feed of rudder position to the ECU either from a GRF 10 or via a 010-11532-00 Rudder Feedback Cable. I assume that it is the latter that you are trying. This file may help, if you don't already have it, http://static.garmin.com/pumac/GHP12_Wiring_Reference.pdf. It looks like it should work in theory but faced with a similar issue I shelled out for a new rudder feedback unit.

 

[lpdsn]

Disregard the above.

The Garmin autopilot is not looking for an N2K feed, but a direct (and indeed analogue) feed of rudder position to the ECU either from a GRF 10 or via a 010-11532-00 Rudder Feedback Cable. I assume that it is the latter that you are trying. This file may help, if you don't already have it, http://static.garmin.com/pumac/GHP12_Wiring_Reference.pdf. It looks like it should work in theory but faced with a similar issue I shelled out for a new rudder feedback unit.

0 out of 10 for there for reading the question.

He's talking about adding an extra gauge (from Faria) to display the rudder angle from a Garmin autopilot not feeding the rudder angle into it. No indication in his post that his Garmin autopilot isn't a complete working system.

 

[blampied]

sorry I should have clarified,
The Garmin hydraulic reactor autopilot is not currently connected to a rudder reference transducer.
The boat already has a Faria rudder position indicator that came with the boat, I’m hoping to hook it up to the Garmin autopilot.
Garmin market a Garmin rudder reference unit which plugs in directly but it costs a fortune and I’m happy with the Faria unit that’s already fitted so would like to use it.

Note
The Garmin reactor does work without a rudder reference input, but as it’s a hydraulic steering system the autopilot doesn’t know which way the rudder has been turned while it was turned off. So the autopilot takes a few seconds to work out which way the rudder is facing when the autopilot is activated. Not a serious problem when out at sea (Maybe not ideal) but I also tend to use the autopilot when traveling along canals and rivers, a few seconds of indecision on a narrow canal is a bit more disconcerting.
But the main reason for wanting to give the autopilot a rudder reference is so when I forget to deactivate the autopilot waiting for a lock gate for example or taking the boat out of gear and coasting to a stop in a marina, as the boat comes to a stop and starts to drift the autopilot pump suddenly start hammering away with the rudder on full lock as it’s trying to turn a stopped boat. With a rudder reference input the autopilot can be set up with rudder position stops.

 

[lpdsn]

I've partially dismantled an old Raymarine one and it was basically just a variable resistor. The Garmin one and the sender of the Faria one are likely to be pretty similar in principle, but the devil will be in the detail.

The doc that ElecGlitch posted includes details of matching the two-wire one using a circuit with an extra 180 Ohm resistor, so in theory it is do-able.

You might want to check the wattage with Garmin, but it probably isn't much. Worst case is about 15V solely through the 180 Ohm resistor, so 0.083A, so about 1.25W. So something two or three times that should be perfectly OK.

 

[blampied]

Thank you all for the feedback so far, I’m still a little confused as to what I need to do.
Looking at Ohms I’ve found a reference on a USA website that lists the Ohms for the Faria rudder reference as three different values.
Port 10. Mid 95. Starboard 180
Is this information of value ?
So Is it a 180 resistor I need?

From the Garmin static page suggested by Elecglitch (thank you)
I can see that the resistor needs to go into the Black Garmin wire.
But I still can’t see how I can connect up the 3 (Black, Red and Yellow) Garmin cables to 2 (Red and Black) Faria cables?

Looking on eBay at 180 Ohm resistors
they seem to range from 0.25w up to 5w does it matter what wattage I order?

 

[lpdsn]

The circuit diagram in ElecGlitch's link is in the "2 Wire Rudder Feedback Units" section. Garmin wire colours identified. The unit labelled as 1 is the other manufacturer's unit, your Faria. You should be able to check the maximum resistance by connecting a multimeter and operating the unit full lock either way.

The doc actually says match the max resistance of the two wire unit, so don't buy the 180 Ohm one till you've checked, but 180 seems the most likely from what you say.

If the resistor is too low wattage it'll overheat. So somethingt over 1.25W should do. Safety margin of your choice.

Remember basic school physics. W=VI, I=V/R and W=IsquaredR

If it were me I'd get a small bit of vero board and a small junction box to mount the resistor and connect the wires neatly.