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post #5 of Old 10-28-2003
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interfacing GPS to Autohelm

I have interfaced a Garmin 162 to a Raymarine (Autohelm) 4000. Personally I love it. (Of course, I am a gadget freek).
The way it works is that you first activate a route on the Garmin. Then on the 4000, you first hit "auto" to engage the autopilot, flip the lever to engage the pilot motor drive, then "track" on the 4000 to get it to recognize the signals from the Garmin. Then the 4000 will beep and ask to turn to the new waypoint and you hit "track" again to confirm the turn. Each time you hit a new waypoint, it will beep and ask you to hit "track" again to confirm the turn. And yes, the reason per previous poster, is for you to visually confirm that it is safe. In the meantime, the 4000 is steering by XTE as well as heading, so I found the steering to be more precise, particularly in a seaway. Also great for staying in channels or away from shallow water. Much better control than just steering to a heading. In a seaway, I have found less wandering when using the track function.

The interface itself is via NMEA--be sure to set the Garmin I/O to NMEA in and out, not Garmin protocol. The wires go from the Garmin to NMEA input of the 4000.
I do NOT connect Seatalk to the 4000--if you want the 4000 to steer to wind direction, then you need a Raymarine wind instrument and Seatalk. I havn''t tried to have the 4000 steer to wind from a NMEA device, though it might be possible.
The NMEA interface is 3 wires, of which only 2 are required.
From memory, I believe the 4000 is labeled + and -, while the Garmin is +, - and gnd or common.
The last time I did this, I first made an error in connecting the GPS - to 4000 -, so check the wire connections. You can see if it worked by hitting the display button on the 4000 and seeing if the XTE display matches the Garmin XTE. Also check the baud rate--it is selectable on the Garmin--I believe it should be 4800 but don''t quote me.

I recently replaced the Garmin with a Raymarine 530 and still used NMEA to connect, rather than seatalk. I have found that Seatalk is problematic--if there is a power surge anywhere in the system, it can kill seatalk on one of the connected instruments, then all crap out. The 4000 is then dead completely, waiting for seatalk to be restored, and even the simple "pilot to a compass heading" won''t work. To restore the simple function, you have to unplug the offending seatalk connection from the 4000--easy to say, but hard to do in a seaway with the 4000 mounted in a navpod.
I had the navpod apart this last weekend, doing some other wiring, so if you are still at a loss, let me know, and I can check out the wire colors. While I have replaced the 162 with the 530, I still have the 162 at the helm, ready to plug one wire into the 4000 if needed.

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