Wire Garmin GPS to ST4000+ autopilot

[py26129]

This may be a stupid question but here it goes:

Our, new to us, boat has an Autohelm 4000+ autopilot to which I would like to connect my GarminGPS, so that the AP can steer to a waypoint based on input from the GPS.

Is this as simple as connecting the NMEA out from the GPS to the NMEA in on the AP and the NMEA in from the GPS to the NMEA out on the AP?

I'd love to hear form comeone who has done this as reading various posts from around the web intruduces a fair bit on confusion.

Many thanks

Matt

[Spyder]

I just followed the same path with the Raymarine Wheel Pilot and a Garmin. It didn't work until I realized it all needed a good ground.
Cheers,

[py26129]

Spyder

Many thanks fo your quick reply.

When you say it needs a good ground, do you mean the ground wire from the Garmin plug and the negative lead from the 12V supply to the ST4000 control unit? If that's not the case, then how did you wire it?

Many thanks again

Matt

[RhythmDoctor]

Originally Posted by py26129

...Is this as simple as connecting the NMEA out from the GPS to the NMEA in on the AP and the NMEA in from the GPS to the NMEA out on the AP?

The answer to this depends on your GPS.

First, unless yours is different from mine, the ST4000+ has no NMEA out. Output is via SeaTalk only. But you only need input to use "track mode."

My ST4000+ has an NMEA input. To run in "track mode," the AP needs more than a simple GPS fix, it wants cross-track error, distance to waypoint, bearing to waypoint, and SOW (if available). These are things that a chartplotter provides. Some GPSs have chartplotter capabilities that provide this. So the answer depends on what capabilities your GPS has. When people tell you that they hooked up their GPS to their AP and it did not work, this may be why.

I have a GPS puck that feeds chartplotter software on a netbook (and to a VHF/DSC/AIS receiver), and the chartplotter in turn feeds its information to the ST4000+. Click here for details on my setup.

[py26129]

Many thanks your your reply. I looked at the details in your other post and find them very clear.

You are right about the ST4000+ not having an NMEA out. As you mention, this requires a Seatalk

Time to go and see what NMEA sentences my GPS will transmit.

Thanks again

Matt