Nema 0183 to linear DC

[ilana]

hello.
I would like to create an autonomy automatic steering system when emergency needed.
Is there a ready product that knows how to get a command from a NMEA0183 protocol machine and to translate it to a linear DC command?
I know that a ship's navigation brain box is doing the job. I'm looking for something simpler that does not need an external control panel.
The circuit I'm looking for can have an output of very low current, even that can not directly operate autopilot DC motor.
Ilan

[Paul L]

What NMEA sentence do you want to translate to a linear DC voltage value?

[ilana]

Hello Paul
I am using Sea Clear as a backup software. I want to use the exit sentence that intended to operate the steering wheel of the ship through a connection to the autopilot.
I have a DC amplifier and a bi-directional driver suitable for a linear DC input signal.
Ilan

[Paul L]

Here is a list NMEA 0183 sentences. Not sure what you are referring to as exit.
Standard NMEA-0183 sentences description

[ilana]

This is a great step for me to understand the NMEA 0183 protocol.
With the Sea Clear software I can see the exit the letters from which the sentence is composed. How do I translate this into a linear electrical value? Is there a circuit that knows how to translate it. Maybe in Arduino one?
Maybe there's a shelf product that knows how to do it?
Ilan

[Paul L]

I don't know what you mean by exit letters. Which nmea sentence do you want to use? The sentences are identified by three letters, such as
GLL - Lat/Lon data

[ilana]

At the end of the week I will be on the ship and check the output of the Sea Clear software composed protocol and what are instructions to the steering wheel. I can see it
Thanks
Ilan

[DotDun]

The reason an autopilot has 'an external control box' is to perform the calculations from the chart plotter (SeaClear software). SeaClear sends the AP bearing to the waypoint (BTW), distance to the waypoint (DTW), and cross track error (XTE) which is how far right or left of the track. The AP also needs a compass input in order to use BTW.

I suppose you might key in on XTE and turn the boat right/left until you see XTE of zero.

[tanglewood]

And most autopilots use a rudder feedback as part of the control loop.

The "device" you are looking for is an autopilot computer. If you do some searching, one or more people have built home-brew AP computers. That's probably what you are looking for.

BTW, by "exit", I think he means "output" as in output sentences.

[Paul L]

Originally Posted by tanglewood

.....

BTW, by "exit", I think he means "output" as in output sentences.

Makes sense. I was just pointing the OP to a place he could start his education on 0183 data. With some education I'm sure he'll conclude that the solution is a proper AP controller.

[smac999]

Originally Posted by tanglewood

The "device" you are looking for is an autopilot computer. If you do some searching, one or more people have built home-brew AP computers. That's probably what you are looking for.

do any of the home brew ones follow route data? or only steer to heading?
that would be even harder to make yourself.

there is a reason there is an "external control panel" between the computer and pump. it's called an autopilot, and it is needed...

[guyrj33]

search the web for the open source autopilot project.

you'll need a computer with a serial data input to receive the NMEA data and an analog output to supply the voltage out.

[TreblePlink]

If you want to use an Arduino, check out the TinyGPSPlus library. Parses out wanted NMEA strings. It would be trivial to then convert to a Pwm output AnalogWrite(). Or do some averaging and whatever else .

I like the Nanos for this simple stuff...

[ilana]

In general I just want a steer to heading. Not to hold a steering wheel for hours during a crisis in the electronic system. There is always a continuous waching shift on the boat.

[ilana]

I was delivering with another person a boat and due to lightning damage we kept the steering wheel for 45 hours. Not nice.
During the overlapping hours, we thought of a simple solution of a magnetic compass needle and two sensors that would identify a deviation in the path, and would fix the ship's cruise with the navigator's electric motor.
The solution is very primitive but may work.