Continuing the theme of giving a flavour of the things involved with wiring a Garmin G3X system, here’s how I’ve been wiring the CanBus.
Garmin uses a CanBus to connect the various LRU’s (Line Replaceable Units, things like the PFD, MFD, Servos and other boxes) so that data can be transferred between them.
In this diagram from the installation manual, Garmin says the shields for each CAN bus wire segment should be interconnected, forming a continuously connected shield from one end of the CAN bus to the other.
Garmin’s installation manual provides guidance on recommended max and min dimensions for the screen pigtail position..
I’ve constructed the CanBus from 2 core 22awg screened cable, M27500-22TG2T14.
The first stage in making a CanBus “Node” is to strip a small segment of insulation from the wire to expose the screen, and remove the insulation and screen from the end to release a length of the 22awg wires.
One method to attach the pigtails to the screen is to use solder sleeves, seen here pre-positioned on the wire.
I found that the M83519/1-2 solder sleeves are the best size for the 2 core wire.
I’ve used 22awg wire for the screen pigtails.
I fixed the pigtails in position over the exposed screen “window” with tape to ensure that they were in the correct place before soldering.
Here’s the solder sleeve in position over the screen window.
Careful inspection ensures the pigtail wire is positioned correctly ready for soldering.
Then the heat gun is used to shrink and activate the solder in the sleeve.
The usual inspection and tug test to confirm a good joint.
Also a continuity test is a good idea to be sure no shorting has occured between the wires under the screen. Applying the heat gun just enough time to get the job done should help prevent these.
I haven’t spotted any shorting issues, so hopefully all will be well … touching wood!
Then the individual wires are joined … carefully cutting a window in the insulation, trimming the other side to length and stripping.
Garmin recommends a short length of heat shrink tubing to cover the screen where the wires exit.
Then I’ve used solder sleeves to make the joints … as before using tape to position the wires as required.
The smallest M83519/1-1 solder sleeves seem best here.
Here’s the result, a white and white/blue wire ready to be inserted into the connector CanBus pin holes.
Finally a ring connector is crimped onto the end of the pigtail ready to attach to the connector.
I’ve found it best to do this after the wires are inserted, so that you can trim to an optimum length … trying to keep the runs as short and straight as possible.
Of course a bad crimp at this stage would be extremely upsetting! But you do so many that your technique should be pretty robust ensuring a good result : )
The other pigtails on this connector are various RS232 connections. These are made in the same way, but because the RS232’s are 3 core, the larger M83519/1-3 solder sleeve is needed to fit over the larger diameter wire.