posted 11-24-2011 11:19 AM ET (US)            

[Editor's note: Actually it was a benefit for Chuck that I deleted his initial method. It did not work. In recreating the method, Chuck revised the method and turned it into something that does work--jimh]

It wasn't just theoretical. I wired my Montauk in a similar manner,
but the boat is forty miles away, and the connector is way up in the
top starboard corner of the console, about as far from a door as you
can get, which is why I wired with a connector - it would be just about
impossible to do anything else up there, and I wanted to be able to
pull the radio or GPS. So I was working from memory, and remembered
wrong. So I'll try again. I'll see if I can get a photo the next
time I'm at the boat (probably Saturday), but only if I don't have
disassemble half the console to get the picture

Get four "flat-two" connectors. These are like a "flat-four" trailer
connector except they only have one male and one female contact.
One example is Cole-Hersee 11172-BP (West Marine p/n 152942)
http://www.westmarine.com/webapp/wcs/stores/servlet/ ProductDisplay?productId=109505 .
Note that this Cole-Hersee part is a kit of two connectors.

Make two four-pin connectors by taping two flat-twos together like so:

 
+-------+
| F   M |
+-------+
| F   M |
+-------+
 

posted 11-25-2011 10:27 AM ET (US)            

The first concept in Chuck's idea is the use of genderless connectors. At first this seems like an interesting idea: a connector that can mate with itself. There several suitable connectors that have this property. A very good example is the Anderson Power Pole connector. They are genderless connectors and mate with themselves. You can create multi-pole connectors with them. The use of a genderless connector is an interesting notion, but it is not the real basis of Chuck's idea. One could, if they wished, use genderless connectors for my wiring devices.

The actual concept of Chuck's idea that is the essential element of his scheme is that the connectors, when mated to each other, flip the transmit signals to the receive signals, and vice versa. It is this concept which is important. In this way, Chuck's idea eliminates the second device, the back plane connectors and their cross-over wiring wiring. If this were possible, it would be a good idea.

As Chuck has described his proposed connector, it is indeed possible to connect it with a similar connector and have the signals cross. However, there is a dreadful side effect of this property--the connector can be mated to its twin in more than one way. The desired cross-over property is only obtained in one of the possible mating configurations. In the other mating configuration, the cross over connection is not obtain. This destroys the fundamental requirement of the solution—it is not a universal solution. It only works when you are smart enough to know which way to mate the connectors.

In addition to not meeting the fundamental requirement of the solution, Chuck's idea is a kludge. (Kludge is an electronic term for sloppy or inelegant solution, notwithstanding its actual functionality) I judge Chuck's idea to be a kludge on this basis:

--the connectors are only available as two-pole devices, and must be assembled into four-pole devices by taping them together;

--the connectors are only available as pre-assembled, pre-molded devices with wiring already attached, and existing devices must be spliced onto the connector's wires, an ugly and hard to work solution;

--the typical pre-wired connector is provided with conductors of 12-AWG or 14-AWG, which are much larger than needed for the currents involved, and the larger wire size makes it more difficult to splice to the usual 22-AWG conductors from the devices.

posted 11-25-2011 11:27 AM ET (US)            

It only mates one way.

There are four ways you can try to put two connectors together.
Here are the four ways. For the top connector you are looking at the front
(pins and socket) side, the bottom connector you are looking
at the back (wires) side. The bottom connector is rotated
90 degrees clockwise in each step going top to bottom.

Works:
+-------+
| F   M |
+-------+
| F   M |
+-------+
+-------+
| M   F |
+-------+
| M   F |
+-------+

Doesn't work:
+-------+
| F   M |
+-------+
| F   M |
+-------+
+---+---+
| M | M |
|   |   |
| F | F |
+---+---+

Doesn't work:
+-------+
| F   M |
+-------+
| F   M |
+-------+
+-------+
| F   M |
+-------+
| F   M |
+-------+

Doesn't work:
+-------+
| F   M |
+-------+
| F   M |
+-------+
+---+---+
| F | F |
|   |   |
| M | M |
+---+---+

Chuck

posted 11-25-2011 12:34 PM ET (US)            

I used color-coded conductors to identify the four poles, using Brown, Red, Orange, and Yellow (the resistor color codes for 1,2,3, and 4).

I made a second connector, identical to the first:

Now I mate them. I agree, they only mate in one way with this new configuration:

Referring to the conductors by their color codes, we see the mating provides

BROWN --> ORANGE

RED --> YELLOW

(and, of course, by definition then)

ORANGE --> BROWN

YELLOW --> RED

posted 11-25-2011 12:57 PM ET (US)            

In my opinion, the implementation of the method using off-the-shelf SAE two-pole power connectors is difficult. My basis for that is my experience in trying to assemble the connector I show above in my photographs.

Taping two separately molded two-pole assemblies together is not particularly easy. The connectors have small ridges on them which prevent them from laying again each other. You might want to use a razor-knife to cut off the ridges to enhance the assembly.

The typical pre-molded connectors come with attached wires using red and white insulation in short lengths. The wiring color code is flipped at one of the connectors, making these pre-made devices have two schemes, which I will call R and S. In the R scheme the red wire is connected to the male pin, and in the S scheme the red wire is connected to the female socket. When making up a set of two four-pole genderless connectors there will be opportunity for a lot of ambiguity in the wiring to the connector if one were to refer to the original color of the wire insulation of the pre-made connector. (This is why I used color tape in my test implementation. It was very difficult to keep track of connector designation without a unique color identifier.)

The mating force of the connectors is high. Since the home-brew four-pole connector is made with adhesive tape, it is extremely difficult to mate two of these together. (That is why I show them not completely mated in my photograph, above.) I never did try fully engaging the home-made connectors. I suspect that disengaging them would be even more difficult.

My objections remain regarding the splicing of existing cables from marine devices to a home-made four-pole genderless connector made from the SAE two-pole power connectors taped together. The wire sizes are much different. In addition, the ambiguity of the color codes (that I mention above) will also make errors in wiring more likely.

posted 11-25-2011 01:03 PM ET (US)            

--you assemble it from individual poles into a multi-pole connector

--it is available with color coded housings so there will be no ambiguity about wiring

--it is not a pre-molded connector with captive wiring, so you can assemble it to an existing cable

The drawback of the Anderson Power Pole is that it is not at all waterproof.

posted 11-25-2011 01:16 PM ET (US)            

I'd love to find a less kludgey connector that's small (so
you don't have to drill a huge hole in the console, salt water
tolerant, and not terribly expensive. I'm not about to
rewire the boat just to change connectors, but I suspect
there's a new chart plotter in my future (I have a Garmin
GPSMAP 162 that's about 12 years old and has a very occasional
intermittent antenna connection), and might well change
then.