Getting PG500 Hdg data to Pilot

[aquabelle]

I have a MFD12 and two heading sensors: a recently-acquired SC-30 and a PG500, which was my original Hdg source. Aside from the MFD12, various Repeat instruments (RD33, etc) and a laptop running MaxSea Navigator also use Hdg….but most importantly, the (0183) autopilot needs a good Hdg feed.

Currently, the PG500 is connected directly to the autopilot AND via its 2nd 0183 output, to an MFD input port. (The SC-30 will be connected via a DRS’s CanBus port). I’d like to set things up so that Hdg from both is available on the network, with priority being given to the SC-30.

I was planning to do this by removing the direct connection between the PG500 and the autopilot and instead, feeding the pilot HDG from a MFD output port. I would then set the SC30 as the priority sensor in the Global settings.

However, having read a post by Johnny Electron back on Jan 30 (Heading-PG500 vs PG700 ), I learnt that sending Hdg from the PG500 via the MFD slows the signal down too much for use by a pilot; he recommended putting the PG500’s output onto the N2K network via a converter instead.

I have a converter and could do this. Have I understood Johnny correctly? Is this the way to go?

 

[Johnny Electron]

I was planning to do this by removing the direct connection between the PG500 and the autopilot and instead, feeding the pilot HDG from a MFD output port. I would then set the SC30 as the priority sensor in the Global settings.

When you drag heading data through the MFD you delay it slightly but most importantly you change how often the data is updated. You do NOT want to use SC30 data to run a pilot after it has been dragged through the MFD. It will be too slow. You are much better off with the PG500 directly feeding in that particular case. (YET, I never recommend your autopilot using a different source of heading than your plotter) Heading is the heart of an autopilot. The SC30 would be a better source of heading for sure, but you have to ensure the data path doesn't reduce the quality of that heading for the purpose you are using it for. If this was a newer pilot (like NavPilot 700) you could connect the SC30 direct to the bus with the pilot. If this was my equipment, I would connect the SC30 down to an established bus with the NN3D. Then put on a IF-NMEA2k2 converter. It would be set to high speed heading mode to give the best quality heading to your Navpilot via 0183.

 

[aquabelle]

So you are saying add a converter to the N2K network set to output HDG at 38.4k and connect the pilot to the converter. I guess I don't really understand the difference between update speed and baud rate. My pilot has a standard 4,000 baud v3.0 0183 port....will it benefit from/cope with the high speed output of the converter ?
Thanks for your patience in explaining.

 

[aquabelle]

Supplementary questions: as well as Hdg, I also need to give my pilot position data (it prioritizes pairs of sentences, starting with RMC, RMB). In the past I have just connected one of the pilot's two NMEA0183 input ports to the GPS signal bus. I'm now wondering if I should send this information at a higher transmit rate also? I have a converter that will do this...or is Hdg the only really critical signal that needs to go at a higher transmit rate?

 

[Johnny Electron]

Your GPS and steering instructions are fine the way they are. There is baudrate and there is update rate and they are different. I don't want to go too far down the rabbit hole, but when you put the IF-NMEA2k2 into a faster heading "update rate", it just happens also runs a higher baud rate to support it. The update rate of heading in normal mode for the converter is every 1000ms but at high speed mode, the update rate is much faster at 100ms. (10 times faster) With heading being the heart of the pilot, the better quality heading roughly means a better preforming pilot.