First, Build a Shed

[efwd]

Nice job Carl. Enjoy the Holidays.

[Cherrybark]

Finally identified the wiring problem on the EIS (Engine) end of the Can Bus. Along with the normal CAN Bus, the EIS has a backup RS-232 cable to the display unit. The connector on the display has three rows of tiny pins. One of the RS-232 pins was inserted in the wrong hole, a "Terminate CAN Bus" as it happens. Relocating that pin solved the bus problem and all of the units are happily chatting away with 0% network errors. One nagging thought - if that pin had been mistakenly inserted in a less disastrous hole, would I have ever known there was a problem. EIS normally communicates on the CAN Bus and until that very reliable (millions of modern vehicles) fails, this backup path is not used.

I stopped in the middle of the covering project to do this wiring for a couple of reasons. First, it was so easy to reach through the fuselage structure to do the work. And second, I wanted to make certain the proposed GMU-11 magnetometer location in the port wing wouldn't be disturbed by the magnetic fields of the strobe and landing light wig-wag operation. I hadn't read of other planes with the solid state magnetometer and didn't want to discover a problem after the wing was covered. Happily, the interference test passed with nary a blip.

Now I can make a few final connections for the Com PTT and headsets, tie the wires in neat bundles, check this job off the list and return to Oratex.

[PapuaPilot]

Glad you found it Carl. Those kinds of problems can be very hard to find. Good thing the connection was not one that let any smoke out.

[Flybyjim]

I am looking at the G3X to install into my SS7. I am not new to building planes but electronics and their wiring is a challenge for me, partly due to a color issue, like seeing blues, browns, reds, green.

How many wires go to different componets say from the main screen to the magnetometer, servos if you are adding auto pilot? Setting up the can buss is there a dedicated line of travel to the different componets such as you have to end at a servo?

[Cherrybark]

The CAN Bus is the backbone of the unit to unit communications network. It only requires two wires that should be in a shielded conductor to avoid electrical noise. The "trunk" or "main line" of the bus has to run very close to each device with a short, say 6", connection to each device with a "T" splice. This time of year, a string of Christmas lights comes to mind. You cannot configure the CAN Bus as a star, or string two or more devices together then splice to the main line. Each device must have it's own, short "T". Garmin includes special "Terminator" connectors to be used at the two devices at the ends of the bus.

My CAN Bus starts at the GEA 24 Engine Interface Module that is mounted on the port electrical tray near the firewall. From there is runs along the back of the instrument panel, down through the central console to connect to the small GPS box mounted behind the seat. It continues to the roll A/P servo behind the pilot's seat, then runs aft to the pitch servo mounted with a KitFox kit towards the tail of the plane. From that rearmost point, the bus runs back forward to the back of the pilot's seat and up along a diagonal tube to a plug close to the rear spar mounting point. The bus continues through the rear spar to the tip of the wing then comes back a couple of ribs to where the GMU-11 Magnetometer is mounted.

At the two ends, the two wires of the bus have pins that are plugged into the terminal plug and the shield is spliced to a ground wire with a ring terminal to connect to the outer shell of the terminal. To attach a device to the bus, the cable is cut and a short piece of 2-conductor, shielded wire is spliced as a "T" - not forgetting to solder the three braided shields together and make everything pretty with shrink tubing (marine grade with glue).

Some units, such as the magnetometer and servos basically only have two wires for power and two wires for the CAN Bus. To be complete, one of the servos does have a short wire between a pin and ground to distinguish between the roll and pitch servos. The busiest units are the display and transponder because they use 3-wire RS-232 connections to communicate with other units. Oddly, the transponder does not even connect to the CAN Bus but only communicates over RS-232.

There are not too many different colored wires to deal with. I used a 4-wire shielded cable to the magnetometer which had white, white/blue, white/brown, and white/green. That one might give you fits but I think you could run the cable, attach pins, and use a VOM with a long wire attached to one of the probes to identify the wires. I used all aircraft grade wire so everything is white. Part of preparing each wire was labeling each end with a printed name inside a clear shrink tube.

Looking through the Garmin G3X installation manual can be intimidating because there are so many possible connections to support different configurations. There really aren't too many connections for our simpler, single engine craft.

This isn't a hard job but it does require a lot of attention to detail and it will take some time to do the work carefully. There is the problem of figuring out how many feet of different, and expensive, multi-strand wires to purchase. I have a magnifying, binocular headband that came in very handy when reading the tiny numbers when inserting pins on connectors.

[Cherrybark]

It was useful to print out sections of the Garmin installation manual for a 3-ring binder. Garmin put the pin assignment diagrams and text separate from the descriptions of mounting the units. Each section of the binder collects a short excerpt for the unit and the related terminal diagram, pin assignment table, and descriptive text. Printing out the entire Garmin manual would be a huge waste!

Once the wiring is complete, you'll probably want to print the 200 or so pages of "Configuration".

[Cherrybark]

Two months slipped by without a post. Slowly got back to work after the Christmas holidays and it's a pleasure to be regularly working on the project. The ugly nest of wires are tidied into laced bundles and that part of the project is complete and tested. A few more wires will be added for the engine but it's nice to have most of the breakers and switches populated.