PG500 new install

[aquabelle]

I am installing a PG500 for the first time. I have connected the center NMEA port directly to my NavNet3D and I have connected the Power/NMEA port to my (non-Furuno) autopilot. I have NOT completed the 'Correcting Magnetic Field Distortion' open water step in installation yet, but I am getting heading output data on both my NavNet3D and on my autopilot.

Two questions: using the port monitor function on my NavNet MFD, I can see I am getting five consecutive sentences of the form $HCHDG,127.3,,,,*45 ( a normal sentence I think) AND after every 5 of these sentences, I get this single sentence: $PFEC,hdcom, N,Er,0010*05....then the 5 standard heading sentences appear again, and so on. I know the $PFEC is a proprietory Furuno NMEA 0183 sentence: but what does it mean and should this disappear when I complete the 'Correcting Magnetic Field Distortion" open water installation step?

Second: although the heading appears on my autopilot initially, within a few moments IF THE NAVNET3D MFD IS NOT POWERED UP, the autopilot generates a Heading Lost error msg. I don't understand how this could happen when the autopilot and the MFD are independently connected to the PG500. In fact, one of the reasons I went with the PG500 was to achieve some redundancy between chartploter and autopilot (if either one of them went down, I expected to still have a heading output on the other). The only connection between the MFD and autopilot is the NAV data sent from MFD to a/pilot when a GoTo command is activated on the MFD...but given the autopilot's loss of Heading data occurs when the MFD is off, no NAV data is being output. Could the problem be related to the periodic $PFEC msg noted above and be likely to disappear once the 'Correcting Magnetic Field Distortion' installation step is completed?

thanks in advance for feedback.

 

[Johnny Electron]

aquabelle
The $PFEC sentence will continue to show up in the data sentence stream. This is normal. This is a special sentence is so we can send rate sensor info to our autopilot and other Furuno products. This sentence is normally ignored by other non-Furuno devices. Company specific sentences are an approved part of the NMEA standard.

Please note: PG500 by default has a 200ms update rate and the NN3D system requires a 100ms or faster rate. You will need to change the default setting to 100ms (para 3.5 in PG500 manual) for the NN3D to work correctly with the PG500.

Concerning your Autopilot error: I have found many other manufacturers’ autopilots tend not to work well with heading data that doesn't come from their own proprietary sensors. You might speak with the manufacturer to see if the PG500 can be used with it. It could be the update rate is also too slow for the pilot and once you make the change for the NN3D it will also help the pilot. The manufacturer of the pilot would be the best to know what the needs are. I do know that Simrad pilots don't tend like the PG500. Many of their customers used our SC30 or SC50 to fill the gap when they had a shortage of heading sensors. I hope your autopilot company can talk you through some settings to make it work for you. If you provide the make and model, maybe some other Forum members will have input that will be useful. Of course the pilot itself might need repair. What is the status of the orginal compass that came with the pilot?

Johnny

 

[aquabelle]

Johnny: thanks for the $PFEC explanation and for the tip about changing to 100ms (I thought 200ms was faster/better, so glad you told me this !) I still don't understand why the autopilot is getting the HDG data fine when the NavNet3D MFD is on but loses it when it is switched off? With the MFD on BUT NO NAV DATA BEING TRANSMITTED, how is the MFD having this effect??

The only common connection I can i.d. is that the NMEA (-ve) of the MFD's Port 2 OUT sending NAV to the a/pilot, shares a common connection terminal on a Ground bus with the NMEA (-ve) wire from the PG500 to the MFD. (The PG500's Gnd is also taken to this same terminal). I wouldn't have thought a common Ground would cause this problem?

(The a/pilot is a CourseMaster 850i; its original proprietary fluxgate compass couldn't output at 100ms AND as I mentioned, I was looking for HDG redundancy and really liked the fact the PG500 has two independent NMEA outputs. In my original set-up the MFD was getting HDG via the a/pilot, not directly from the fluxgate. The specs for the a/pilot say its NMEA port is designed for NMEA0183 v3, with a baud rate of 4800. Character format is start bit, 8 data bits, LSB first
MSB (bit 7) = 0, no parity bit,
1 or 2 stop bits)

A/pilot manual says the system looks for the HDG (or HDT) sentence and that variation and deviation sentences are ignored. (Variation can be separately entered into the a/pilot system)

thanks in anticipation for your further comments

 

[Johnny Electron]

Aquabelle
You said

I still don't understand why the autopilot is getting the HDG data fine when the NavNet3D MFD is on but loses it when it is switched off?

It might help to know how you got the MFD wired to the compass. If you have it wired bidirectional to the compass, the MFD might be sending the compass RMC and allowing the compass to output TRUE. If your pilot is using it (TRUE) and you turn off the MFD, the MFD will stop sending RMC to the compass, and the compass will stop sending TRUE. (chain of events) Again… It is what you pilot is looking for is the key. If my above example isn’t the issue, then maybe the compass power is going down when you power off the MFD. Check the compass status light with the MFD turned off and tell me what they are showing. If all else fails… Use the autopilot compass with the autopilot and the PG500 with the NavNet and all should be happy.
Johnny

 

[Johnny Electron]

Aquabelle

The only common connection I can i.d. is that the NMEA (-ve) of the MFD's Port 2 OUT sending NAV to the a/pilot, shares a common connection terminal on a Ground bus with the NMEA (-ve) wire from the PG500 to the MFD. (The PG500's Gnd is also taken to this same terminal). I wouldn't have thought a common Ground would cause this problem?

Not exactly sure how you got your grounding connected. NMEA cables have shield, but they should not be connected to ANYTHING. Furuno NMEA has a + and - for each output and input. Is it possible to draw out how you have this stuff connected, and then attach it to your reply, so we can see what is what?

 

[aquabelle]

Johnny: the compass remains powered on and the status light remains lighted when the MFD is closed down, just as it should. No doubt I've done something dumb with the connections, probably the grounds. Here's a (very amateur) diagram...appreciate the time you are taking to help me sort this !

 

[Johnny Electron]

Aquabelle,
Your drawing was very helpful. Thanks for posting it. Your wiring is very wrong and might be the cause your problems. I will draw you out a correct drawing and post it shortly. You are grounding/shorting out the negative side of your RS422 NMEA 0183 communications. Unlike RS232; RS422 has a signal on the negative side and should NOT be taken to ground.
Johnny

 

[Johnny Electron]

Aquabelle,
See below: (please note this is just one example of doing it. Our NavPilot wiring would be via the Power/data cable for example)

 

[aquabelle]

Johnny: hugely helpful, thanks. I understand now about not taking the -ve side of the NMEA0183 connections to Ground. But if Gnd is removed, is it ok to have the -ve sides of the IN and OUT ports at the one terminal?...or must these be literally kept separate as you have drawn?

ALSO: my autopilot's manual says the pilot looks for pairs of sentences starting with RMB & RMC; then RMB & GLL; then APB & GLL, etc and STOPS AFTER THE FIRST COMPLETE PAIR. Is there any reason therefore to check-box more than RMB & RMC? (Elsewhere in the NN3D documentation it says not to check more boxes than are needed.)

The good news: over the weekend I finally got to carry out the turn-in-circles Magnetic Field Distortion routine. It produced a heading output within 1 degree of the heading showing on my magnetic compass and when I tested it out following routes I created via the NN3D MFD, the result was superb: the best autopilot response I've ever had, by a long shot !

 

[Johnny Electron]

Aquabelle

is it ok to have the -ve sides of the IN and OUT ports at the one terminal?...or must these be literally kept separate as you have drawn?

You MUST keep these separate. These wires have a signal running on them. You should not ground them or attempt to tie them with other negative signals from other ports. Doing so, will not only keep things from working correctly, will also likely lead to damage of the equipment.

The NMEA sentences I provided, as an example, are some of the basic ones used when you are not exactly sure what the pilot manufacturer is looking for. If you know the exactly what your pilot is looking for; use the settings suggested by the pilot manufacturer.

It’s great news that you got the compass calibrated and working so well.
Johnny

 

[aquabelle]

Thanks Johnny....I have now changed the wiring to the configuration you provided and all is working well.

One final (I hope) question: in normal use, is the AUTO led on the PG500 left on, or is it only activated from time to time when the fluxgate heading is out of whack with the magnetic compass bearing? Is there any problem in leaving the AUTO led lighted or should only the STATUS led be on ? (I noticed both the AUTO and STATUS leds were lighted/un-blinking after I completed the installation Auto Mg Variation routine. Both stayed this way until I touched the AUTO button, which extinguished the AUTO led....but should I have left it lighted?)

regards

 

[Johnny Electron]

aquabelle,
Congrats on the progress.

The Auto light should normally stay lit after you complete the Automatic Distortion
Compensation. Your current status (Auto and Status lit solid) is a good state to be in for normal operations. Sounds like you have won the battle. (if you turned off AUTO, just hit the button again to turn it back on)
:jump
Johnny

 

[aquabelle]

Johnny: just to complete my understanding of the PG500's operation: can you confirm the NMEA/Pwr Out and NMEA Out ports send IDENTICAL NMEA sentences, HCHDG & $PFEC,hd, and send at identical rates (100ms if that is what is programmed in, say) please? I'd like to understand whether it makes any difference which port is used to connect to the MFD vs the autopilot.

tks again

 

[Johnny Electron]

aquabelle,
The output NMEA on the power/data port and the NMEA (center) port are exactly the same. With that said, both ports also have input wires BUT you CAN NOT use both inputs. You must pick one or the other if you plan to input Magnetic variation (RMC or VTG) to the compass. (see page 9 of PG500 manual)

*Only one port can be for Input.

SO... If you change the baud rate or update rate for NMEA,etc... it changes both NMEA outputs the same.
Johnny