Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-04-2012, 13:37   #1
Head in a locker
 
Cavalier's Avatar

Cruisers Forum Supporter

Join Date: Dec 2010
Location: Houston, TX
Boat: Beneteau 461 47'
Posts: 879
Images: 1
MOB NMEA sentence

Ok,

Thinking caps on!

I have a NASA marine MOBi system with 6 fobs. It's the usual MOB system whereby if anyone falls overboard (while wearing a fob) and the fob goes out of range of the central station, an alarm goes off and the LCD shows which tag it was.

I also have a Raymarine C-series wide, this permits input through the seatalk (NMEA0183) bus to activate the MOB function on the chartplotter. This works exceptionally well with Raymarine's lifetag system which connects to the chartplotter via the seatalk input. However, Raymarine's lifetag system is over twice the cost of the NASA system.

I've thought about tapping/splicing into the audible alarm system on the NASA MOBi so that I could drive a simple signal circuit to activate a circuit (which i've yet to design) sat on the seatalk bus which can plex a simple NMEA sentance into seatalk stream.

Does anyone have any thoughts on what the MOB sentence is for NMEA0183? I'm assuming it has to be something simple and doesn't include GPS coordinates etc.. my guess is that it has to be something which just flags the MOB button hit in the system.. or is it a waypoint-type (WPL) message?

Any thoughts or feedback would be appreciated.

Phil
__________________

__________________
Cavalier is online now   Reply With Quote
Old 09-04-2012, 14:09   #2
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again
Boat: Sailboat
Posts: 1,047
Re: MOB NMEA sentence

Need to find my old thinking head..... I looked into similar things three years ago, so maybe my info is outdated, a bit:

  • I don't think there is a NMEA MOB sequence. There is a sequence to cancel the alarm: "PNATA".
  • The old Raumarine seatalk-nmea box has a manual which lists the commands it translates: http://www.raymarine.com/submittedfi...81166_3www.pdf
  • The Raymarine C/E series does translate the Seatalk MOB to the NMEA sentences BWC, BWR and RMB. These are standard sentences for bearing to waypoint and navigation to waypoint. The waypoint ID in these sentences is "MOB".
  • I did try to set a waypoint in my Furuno GPS as MOB, select GOTO WAYPOINT and the Raymarine chartplotter shows the MOB waypoint, but doesn't issue the alarm.

Thoughts?

Dirk

EDIT: We have the LifeTag if you need any testing!
__________________

__________________
LeaseOnLife is online now   Reply With Quote
Old 09-04-2012, 14:27   #3
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again
Boat: Sailboat
Posts: 1,047
Re: MOB NMEA sentence

This might not be what you want (not using the chartplotter), but might help others trying to accomplish similar things.

We went away from using a proprietary chartplotter (only use it for radar these days). Instead we use PC navigation programs with an external monitor.

One program I have running all the time is "NavMonPc", NavMonPc

Besides the dials, and graphing wind, temps, depths, etc, it has the ability to read one of the handshake lines of a RS232 port to detect an MOB. You only have to connect your switch-output of the MOB-system, maybe with a pull-up or pull-down resistor.

When this RS232 handshake line is switched, NavMonPc will sound an alarm via the PC speaker and starts guiding you via the "AIS-screen" (looks like a radar), towards the last known position of the MOB.

More in the manual for NavMonPc: http://navmonpc.com/UserGuide/NavMonPc-UserGuide.pdf


Dirk

PS: The developer of NavMonPc uses the handle "Paul Elliot" on this forum
__________________
LeaseOnLife is online now   Reply With Quote
Old 09-04-2012, 14:49   #4
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: MOB NMEA sentence

Quote:
Originally Posted by Cavalier View Post
Ok,

Thinking caps on!

I have a NASA marine MOBi system with 6 fobs. It's the usual MOB system whereby if anyone falls overboard (while wearing a fob) and the fob goes out of range of the central station, an alarm goes off and the LCD shows which tag it was.

I also have a Raymarine C-series wide, this permits input through the seatalk (NMEA0183) bus to activate the MOB function on the chartplotter. This works exceptionally well with Raymarine's lifetag system which connects to the chartplotter via the seatalk input. However, Raymarine's lifetag system is over twice the cost of the NASA system.

I've thought about tapping/splicing into the audible alarm system on the NASA MOBi so that I could drive a simple signal circuit to activate a circuit (which i've yet to design) sat on the seatalk bus which can plex a simple NMEA sentance into seatalk stream.

Does anyone have any thoughts on what the MOB sentence is for NMEA0183? I'm assuming it has to be something simple and doesn't include GPS coordinates etc.. my guess is that it has to be something which just flags the MOB button hit in the system.. or is it a waypoint-type (WPL) message?

Any thoughts or feedback would be appreciated.

Phil
You would need a custom sea talk interface which generated a yet unknown MOB alarm sentence. Could be done, not worth it really,
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 09-04-2012, 15:00   #5
Head in a locker
 
Cavalier's Avatar

Cruisers Forum Supporter

Join Date: Dec 2010
Location: Houston, TX
Boat: Beneteau 461 47'
Posts: 879
Images: 1
Re: MOB NMEA sentence

Quote:
Originally Posted by LeaseOnLife View Post
This might not be what you want (not using the chartplotter), but might help others trying to accomplish similar things.

We went away from using a proprietary chartplotter (only use it for radar these days). Instead we use PC navigation programs with an external monitor.

One program I have running all the time is "NavMonPc", NavMonPc

Besides the dials, and graphing wind, temps, depths, etc, it has the ability to read one of the handshake lines of a RS232 port to detect an MOB. You only have to connect your switch-output of the MOB-system, maybe with a pull-up or pull-down resistor.

When this RS232 handshake line is switched, NavMonPc will sound an alarm via the PC speaker and starts guiding you via the "AIS-screen" (looks like a radar), towards the last known position of the MOB.

More in the manual for NavMonPc: http://navmonpc.com/UserGuide/NavMonPc-UserGuide.pdf


Dirk

PS: The developer of NavMonPc uses the handle "Paul Elliot" on this forum
Dirk,

Thanks for this.

I did have a look at the NavMonPC app at some point in the past. I currently use a PC, but use it to connect via the SeatalkHS (cat5e) network to the Chartplotter so I can plan on Raytech and upload at the boat. That way I avoid needing to have a PC on all the time, and can rely on the chartplotter to be the 'hub' of the system.

That's got me thinking, however.. as I remember that the C-series can display the IDs of NMEA devices it can see on the network - i can't remember if it displays a sentence/sequence list.

Does your NavMonPC software intercept anything of value when the Lifetag's activated? I'm wondering whether it's a special string which isn't a standard string which only the raymarine MFDs understand.. it would explain why it's on the Seatalk and not available on the standard NMEA...

I know that the waypoint data is only outputted on the bus once at the start of each waypoint and that you can use the associated sentences to kick-off waypoint alarms. I guess, like you mentioned that the system could be outputting a waypoint with blank LAT/LON with the name "MOB".. that would appear on your MFD straight-away, if you were right on top of it then the waypoint alarm would sound.. any thoughts?

Eventhough it'd be an interesting mini-project, and if I go on with it i'd be sure to upload the details/circuits to this forum so other people can implement electronic MOB switches in their system etc. - i may end up putting my MOBi and 6 lifetags on ebay and buying a lifetag system instead! I saw that the lifetag also has a 12V output on the base station when activated so you could use that to drive a DC-DC relay and kick start all sort of activities.... such as the deck-flood being turned on or
.... like the kettle being activated

Phil
__________________
Cavalier is online now   Reply With Quote
Old 09-04-2012, 15:15   #6
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again
Boat: Sailboat
Posts: 1,047
Re: MOB NMEA sentence

Quote:
Originally Posted by Cavalier View Post
Dirk,

....

Does your NavMonPC software intercept anything of value when the Lifetag's activated? I'm wondering whether it's a special string which isn't a standard string which only the raymarine MFDs understand.. it would explain why it's on the Seatalk and not available on the standard NMEA...
I have to disappoint you, for now: Since we run the PC all the time, but no chartplotter, our setup is: MOB (switch) -> NavMonPc -> RS232 -> OpenCPN.

The chartplotter is pretty standalone, only getting the GPS pos from the Furuno GPS.

I should have the cable to run a seatalk connection from the MOB to the Raymarine. Then I need to capture the NMEA out from the Raymarine, which I am not doing today. Can be done, some day...


Quote:
Eventhough it'd be an interesting mini-project, and if I go on with it i'd be sure to upload the details/circuits to this forum so other people can implement electronic MOB switches in their system etc. - i may end up putting my MOBi and 6 lifetags on ebay and buying a lifetag system instead! I saw that the lifetag also has a 12V output on the base station when activated so you could use that to drive a DC-DC relay and kick start all sort of activities.... such as the deck-flood being turned on or
.... like the kettle being activated

Phil
There might be a lifetag base station plus 3 life tags for sale , =ours. I think the future is in PLBs with an AIS transmitter.... if one wants to spend the money.

Dirk
__________________
LeaseOnLife is online now   Reply With Quote
Old 09-04-2012, 15:21   #7
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: MOB NMEA sentence

Cavalier, I think your getting your NMEAs mixed up. NMEA0183 doesn't have device IDs, NMEA2K does.

Seatalk is a closed system, its a multi master RS485 system, it has been partially reserved engineered, but Ive never seen any of the MOB stuff, which is later, reengineered. ( could be easily done though).

little ATmega16, a few drivers chips and a bit of code, hey presto, of course

dave
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 09-04-2012, 15:44   #8
Head in a locker
 
Cavalier's Avatar

Cruisers Forum Supporter

Join Date: Dec 2010
Location: Houston, TX
Boat: Beneteau 461 47'
Posts: 879
Images: 1
Re: MOB NMEA sentence

Quote:
Originally Posted by goboatingnow View Post
Cavalier, I think your getting your NMEAs mixed up. NMEA0183 doesn't have device IDs, NMEA2K does.

dave
You're right: i'm being a dummy!

I was even considering getting hold of a RaspberryPi to use as a first stage dev-kit: much cheaper than a Rabbitboard and it's not like i'll be using the PWM section at anypoint soon. I know you can get 232 and 485 daughters for it - the TCP/IP stack is already there. Could be handy to have that sort of sandbox to understand what works and what doesn't before committing to something more simplified, to task and bespoke - maybe with an M1 or something.

Apparently, the demand for the RaspeberryPI has been so great that they're already on back-order..

Phil
__________________
Cavalier is online now   Reply With Quote
Old 09-04-2012, 15:51   #9
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: MOB NMEA sentence

on back order, there impossible to get, Im in the first wave, these have been sent back to china to undergo CE and UL certification, I think well see them 2013 at this rate. sheeeh.

why so you need aTCPIP stack, you can't generate MOB via sea talkHS.

dave
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 09-04-2012, 15:55   #10
Head in a locker
 
Cavalier's Avatar

Cruisers Forum Supporter

Join Date: Dec 2010
Location: Houston, TX
Boat: Beneteau 461 47'
Posts: 879
Images: 1
Quote:
Originally Posted by goboatingnow

why so you need aTCPIP stack, you can't generate MOB via sea talkHS.

dave
I wasn't thinking in relation to this problem: more the general flexibility as a platform (for the price): but then, as you say, how on earth are you going to get hold of one before the 4 horsemen of the apocalypse rock-up
__________________
"By day the hot sun fermented us; and we were dizzied by the beating wind. At night we were stained by dew, and shamed into pettiness by the innumerable silences of stars."
Cavalier is online now   Reply With Quote
Old 09-04-2012, 16:06   #11
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: MOB NMEA sentence

Quote:
Originally Posted by Cavalier View Post
I wasn't thinking in relation to this problem: more the general flexibility as a platform (for the price): but then, as you say, how on earth are you going to get hold of one before the 4 horsemen of the apocalypse rock-up
too right, can't wait though cheap as chips. If they sort out the volumes it will be a great little development platform. I suspect well see loads of adder boards, probably take over from arduino

Dave
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 09-04-2012, 16:44   #12
Registered User
 
Nicholson58's Avatar

Join Date: Jan 2011
Location: Live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 3,466
Images: 83
Re: MOB NMEA sentence

Quote:
Originally Posted by Cavalier View Post
Ok,

Thinking caps on!

I have a NASA marine MOBi system with 6 fobs. It's the usual MOB system whereby if anyone falls overboard (while wearing a fob) and the fob goes out of range of the central station, an alarm goes off and the LCD shows which tag it was.

I also have a Raymarine C-series wide, this permits input through the seatalk (NMEA0183) bus to activate the MOB function on the chartplotter. This works exceptionally well with Raymarine's lifetag system which connects to the chartplotter via the seatalk input. However, Raymarine's lifetag system is over twice the cost of the NASA system.

I've thought about tapping/splicing into the audible alarm system on the NASA MOBi so that I could drive a simple signal circuit to activate a circuit (which i've yet to design) sat on the seatalk bus which can plex a simple NMEA sentance into seatalk stream.

Does anyone have any thoughts on what the MOB sentence is for NMEA0183? I'm assuming it has to be something simple and doesn't include GPS coordinates etc.. my guess is that it has to be something which just flags the MOB button hit in the system.. or is it a waypoint-type (WPL) message?

Any thoughts or feedback would be appreciated.

Phil
look at the Brookhouse multiplexers. I think they handle Sea Talk.
__________________
Nicholson58 is offline   Reply With Quote
Old 09-04-2012, 16:49   #13
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: MOB NMEA sentence

Quote:
Originally Posted by Nicholson58 View Post
look at the Brookhouse multiplexers. I think they handle Sea Talk.
They only support a very small number of Seatalk messages, no good for this application
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 27-08-2012, 11:12   #14
Registered User
 
nigelmercier's Avatar

Join Date: Jul 2011
Boat: Bavaria 47
Posts: 172
Re: MOB NMEA sentence

Quote:
Originally Posted by Cavalier View Post
... input through the seatalk (NMEA0183) bus to activate the MOB function on the chartplotter.
Some confusion here, SeaTalk and NMEA0183 are very different. As far as I am aware, a MOB button creates a normal waypoint via NMEA with a flag to indicate its nature.

Quote:
Originally Posted by goboatingnow View Post
Seatalk is a closed system, its a multi master RS485 system, it has been partially reserved engineered ...
I've managed to get hold of a schematic diagram for Raymarine ST60 instruments, including the SeaTalk components. I'm not confident that the SeaTalk emulator circuits that are available are sufficiently robust, so I'm looking for alternatives. The bus is indeed similar to RS485, but is single wire, however I'm hoping that it may still be possible to use an RS485 driver to implement this.
__________________

__________________
Nigel
Got a Bavaria? Want a Bavaria Forum? Click here!
nigelmercier is offline   Reply With Quote
Reply

Tags
mob, nmea

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:18.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.