Hello -
I've got an Autohelm 800 (the one with the pushbottons, not the
compass). I understand that it does not accept NMEA-0183 input except
when the Radio Navigation Interface is used. The Radio Navigation
Interface is a discontinued product. Therefore, I intend to make my
own.
So long story short, I'm looking for information on the 4-pin
connector at the underside of the unit. I understand that the
windvane device or the remote control unit can be plugged into this
connector to control the device. I figure if I can produce the
correct signals for those inputs, I can create a device that
interprets NMEA signals from my GPS and produces the appropriate
commands for the autopilot.
Does anyone have any knowledge whatsoever about those pins, or a
circuitry diagram / schematic for the autopilot.
Thanks for your time!
-Ben

Ben, I have some general and some specific information and circuit diagrams
on these autohelm (pre-ST) equipment.. The compass and control circuitry is
basically the same on all of them.

I even have a circuit diagram (reverse engineered) for the ZO75 radio
interface that you mention. However it would be difficult to duplicate this
without the code for the 8749 processor chip.

You can find these on my web site at
http://hood.hctc.com/~esteve/private/manuals/

I have a Z075 interface if someone can read and duplicate the 8749 /w code.
From there, it would be fairly simple to build the rest of the circuit..
Failing in that, you can plagiarize the circuit and operating procedures in
your attempt to get the NMEA 183 to fuction with your AH800.. (the AH800
manual I have is for the type with the compass on top but the control
diagrams elsewhere should be of some help to you.

Good luck, I haven't been able to get NMEA to my AH3000 even with the Z075..
Let me know how you make out.

Steve
s/v Good Intentions

Hey Steve -
Great information - thanks a bunch! By the way - very impressive
project with "Good Intentions".
I am lucky to work with a bright electrical engineer (I'm a Computer
Scientist myself) who was able to quickly explain the ZO75 schematic
to me. His explaination left me with a couple of questions that I
thought you might know answers to:
First, the obvious one, I can't quite make out the hand-written
notation in the bottom-left corner of Z075InterfaceSch.jpg - can you
let me know what it says?
Second, do you know what IC2 in the ZO75 "does?" That is, does it
simply change the serial input to another sort of signal the autohelm
interprets, or does it sends signals such as "steer left", "steer
right" by activating the appropriate pin on the connector?
I'm really hoping for the second scenario - because that would make
it easy for me to use my laptop to write a program to interpret the
NMEA messages, and output "steer left" "steer right" commands on my
parallel port, and amplify them to the appropriate level before
inputting them into the autopilot.

Thanks again for your help!
-Ben

"Steve" wrote in message ...
Ben, I have some general and some specific information and circuit diagrams
on these autohelm (pre-ST) equipment.. The compass and control circuitry is
basically the same on all of them.

I even have a circuit diagram (reverse engineered) for the ZO75 radio
interface that you mention. However it would be difficult to duplicate this
without the code for the 8749 processor chip.

You can find these on my web site at
http://hood.hctc.com/~esteve/private/manuals/

I have a Z075 interface if someone can read and duplicate the 8749 /w code.
From there, it would be fairly simple to build the rest of the circuit..
Failing in that, you can plagiarize the circuit and operating procedures in
your attempt to get the NMEA 183 to fuction with your AH800.. (the AH800
manual I have is for the type with the compass on top but the control
diagrams elsewhere should be of some help to you.

Good luck, I haven't been able to get NMEA to my AH3000 even with the Z075..
Let me know how you make out.

Steve
s/v Good Intentions

"Ben" wrote in message
om...
notation in the bottom-left corner of Z075InterfaceSch.jpg - can you
let me know what it says?

That is a sketch of the connector "from back" at 2 oclock "black", 4 oclock
"green" 8 oclock "blue" and 10 oclock "shield"

Second, do you know what IC2 in the ZO75 "does?" That is, does it
simply change the serial input to another sort of signal the autohelm
interprets, or does it sends signals such as "steer left", "steer
right" by activating the appropriate pin on the connector?

IC2 is the central 2K rom single chip computer and receives the NMEA 183
sentence on T1 (pin 39). The processor finds the Xtrac Error in the
sentence, determines if it is to port or starboard of the course and send
out a course correction on P23 (pin 24) or P24 (pin 35)..

it easy for me to use my laptop to write a program to interpret the
NMEA messages, and output "steer left" "steer right" commands on my
parallel port, and amplify them to the appropriate level before
inputting them into the autopilot.

If you receive the NMEA 183 on the Serial port of the laptop, process it
with your program and output it via a parallel port. Then just replicate the
relay circuit of the interface to control the AP remote connector..

Good luck..

Steve
s/v Good Intentions

Steve,

I have an Autohelm 800. Do you know of any radio navigation interfaces for sale? Thanks.

Todd

Ben,

Did you get the Radio navigation interface that you posted about worked out. I am looking for one if you have any for sale. Thanks.

Todd

Dear Steve and Ben,

I know this threat is a long time ago, but I was wondering if you ever made the home made Z075 to work?

Please let me know as I am looking for the coding of the 8749.

Thanks,

Mark