Sunday, January 29, 2012

Electronics

Due to work load and weather, not much have been done for a while.  The 3 m tiller extention weighed in at 380 grams and is more than sufficient rigid, but I think I will add a 45/45 biaxial sleeve for longevity.

I have been trying to get all the electronics talking together, which has proven to be a tough task.  I have the Nexus NX2 system, a Lowrance HDS 8m plotter, a Garmin HVS 17X GPS antenna, a VHF radio with built in AIS receiver and a ST 2000+ tiller pilot.  They are all supposed to speak NMEA 0183 but it seems there are a bit different dialects.  My solution, as it seems right now, will be a ShipModul Miniplex-2E, partly because I also want to create a WiFi zone to transmit data to iRegatta. As I would like to transmit to several units, as far as I have been able to establish, I will have to set up a router, and one with an external antenna as the carbon hull will effectively block the signals.

Another thing I have spent some time pondering about is where to place the different units.  Should the plotter be bulkhead mounted or on some sort of arm?  Where would the Nexus instruments be then?  The compass should be on it's own to avoid interference.  Everything should be viewable from everywhere.  Obviously some compromise have to be done. This is what I think:  The compass on the starboard side.  The plotter on port side.  The Nexus instruments either on the pop top, it would need a cowling about 40mm high to make room, or on some sort of pod like the F-32SR Jailbreak.

Hopefully things will soon start to happen, I'm really looking forward to start the season.  However, the snow is still safe with temperatures tending to stiffen water significantly.  I will probably have access to a large heated room and will try to get the mast faired and painted during week 7. Not many heated workshops are 11m or more long......

Inputs on the above appreciated, as always!

11 comments:

CrashGybe 22 said...

Hi Tor,
Had seen the Jail Break "pod" before but mounted on top of the hatch. Fine if is not carbon so the option used there is a good one and one that I will also consider. I am mounting the Garmin GPSMap750 on the starboard side so I can see it better on starboard tack at the start line. I went Tacktick so have the same "wireless" issues.

I have not hooked up all my electronics yet as I have not got the compass unit but I know a big problem with 0183 is the sentence length and speed so the miniplex looks like a good idea. I will be doing a custom embedded device based on the netduino to add processing logic for things like distance to start line and distance to lay line as well as recording to SD. I don't have an iPad but the iregatta software looks tempting....

Andrew
www.andrew-mcleod.com

Tor Rabe said...

Thanks Andrew. I think I'm off the pod idea. I'm afraid it will sooner or later be ripped off by a rope. I will build the instruments in to the pop top, although that will give a very limited visibility from the nets.

What limits the rest of my choices is the safety compartment. I put that on port side. Which means my cooker/heater will go on starboard side which in turn places the electrical panel on port side. Then I will have to have the compass on starboard side and port side is what is left for the plotter. It seems that it is not easy to think of everything during the building process, although I have really tried.

The iRegatta can run on Android as well, so you won't have to mix any kind of fruit in to the basket.

CrashGybe 22 said...

Hi Tor,
I had also considered the side of the cabin/cockpit coaming for the display instruments and have not ruled it out completely yet. This is probabily the best visibility from the net but does double the instrument costs.

I have made the same decision on the safety compartment, because you put it on that side ( and because it would be on the footpath side when the boat is on the roadway ) so have the same issue with the electrical panel but why are you having problems with the compass? Put it somewhere else. Are you talking about a standard magnetic visual compass or an electronic one?

Andrew
www.andrew-mcleod.com

Tor Rabe said...

I actually considered the large Nexus displays at the bottom of the mast, one each side. I found out that it would be cheaper and provide more info to all crew setting up a wifi zone and let everyone use iRegatta or something similar on their existing smartphones or whatever.

I'm concerned with placing the magnetic compass too close to the wiring behind the electrical panel. Maybe it's not that big concern.

CrashGybe 22 said...

Hi Tor,

As we are dealing with DC not AC so there SHOULD be no interference from the electrical panel at all. Pure DC will however have AC induced in it from devices that use switch mode power sources eg where they reduce voltage from 12V to 5V such as the GPS.

We are also dealing with Carbon here and as per lenz's law a conductor ( the carbon laminate ) in a moving magnetic field ( AC from a wire) will generate eddy currents effectively cancelling the magnetic influence via "back EMF" ie http://en.wikipedia.org/wiki/Counter-electromotive_force . This will depend on the electrical resistance of the laminate but we also have 2 layers so we have twice the protection.

I actually think that there may be little interference from the electrical systems, problem is the earth's magnetism is also relatively weak so influence will be exponential in nature relative to distance.

If the compass was in the pop top it would be away from all sources of magnetism leaving both sides free for electrical equipment.

That was very deep for a Saturday.

Andrew
www.andrew-mcleod.com

Tor Rabe said...

whow! This was an appreciated refreshment on electro magnetic physics.

CrashGybe 22 said...

But did it help?

:-)

Andrew
www.andrew-mcleod.com

Silas said...

Induced magnetic fields are not the problem with the electrical panel or other electronics. It is hard iron errors from fasteners and other ferro-metallic elements inside the fuses, switches, etc that you want to keep the compass away from. For most part, this is not a big distance, but some things such as plotter, VHF, etc can have a pretty substantial magnetic field.

Granted, these are fixed magnetic disturbances and can be accounted for with a deviation card which one needs to make anyways, but I had it ingrained pretty heavily in me as a principle of good seamanship that a deviation card is not a substitute for a well planned compass installation.

Currently, due to a poorly planned compass install I get deviations up to about 15 degrees. Despite it being a major pain in the ass, I am considering moving my compass to the other side of the companionway this spring.

Silas
Silas

CrashGybe 22 said...

Totally agree Silas, that then poses the question. Which has more perm magnetism, the heater or the other equipment?

Either way the correct approach of a deviation card or magnetic correction should be applied if this is going to be critical for navigation.

My approach is to use a fluxgate compass that is integrated into the electronics. I need to do this purely to correct for the mast rotation for the wind instruments. I will be able to place it virtually anywhere that is away from other stray sources. Most of the sailing that we will be doing does not require a compass as you can see the marks or the surrounding area.

I am still leaning towards the pod idea or even permanent mount on the pop top for the instruments.

Andrew
www.andrew-mcleod.com

Tor Rabe said...

The heater will be either under the cockpit seat or outboard in the sette backrest, which ever I am able to make the most clever solution. On the other side there will be the VHF, and the switch panel.
Andrew, if you have a rope proof pod idea, would you please put a sctetch up on your blog?
I also have two fluxgate compasses, one in the mast, but I think every boat should have a compass in the cockpit that do not rely on technology to work. Of course not a big deal if you are just racing around cans.
If I place the compass in the pop top, that would probably be the position furthest away from metal possible. You could probably go with this solution as well Silas, and you will be able to do much of the work in your basement.

Anonymous said...

I got a Silva 85 Regatta compass placed on the railway, just in front of the port beam. Since I'm sailing a Corsair Sprint, I'ts still in front of the tiller when sitting in the cockpit.

Btw, great blog. I have been following it anonymously for a very long time.