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Twin G5 install

D

Dragonfly

Active Member
Just doing a twin G5 install with CAN bus to a single GMU11.

All the wiring appears to be as it should, with GMU11 at one end to single G5 then daisy chained to a second G5 (bare in mind I have quadruple checked the wiring).

Termination adaptors are fitted to the ends GMU11 and the end G5) but not to the mid point node.

One is operating as Attitude (Airspeed, Alt etc) with intention to take data from the GMU11 also, second is DG only also utilising the GMU11. Individually they work done on the CAN bus but as soon as I fit the two on the bus it shows a Network Address Conflict.

Can't for the life of me figure it out.

Any thoughts.
 
Pin 3 of the AI G5 is left open, pin 3 of the HSI G5 (unit ID) needs to be tied to ground.

Does that help?
 
How great is this community? Within 2 minutes you have a good answer to your question!

To add to Noel's answer, the G5 units have ID pins to tell the system which G5 is in charge and which is the #2 unit. If they are both trying to talk on the network as the unit in charge, you have a network address conflict.

There should be no connection to pin 3 on G5 #1 and pin 3 should be grounded on G5 #2.

Thanks,
Levi Self

Team X Project Manager
 
Last edited:
While on the subject. I notice that the wiring of the intermediate nodes of the CAN bus is different between the G5 manual and the G3X Touch manual. In the G3X Touch manual, and at the AEA Experimental Avionics class the intermediate nodes show the shields of the CAN pairs connected between the individual can cables and not bonded to the backshells. The G3X manual then shows each end of the CAN bus does bond the shield to the backshell at those two locations only. However, the G5 manual shows every CAN node with the shields always bonded to the backshells, whether at the terminated LRU or any intermediate node.

I have always done it as shown for the G3X. During the AEA class we were told there had been trouble with all nodes being bonded to the backshells and that bonding the shielding to the terminated LRUs only (at the end of the CAN bus) was best.

Now the manuals for the G5 (experimental or STC) show every node bonded to the respective backshell. Is there a preferred configuration on a dual G5 set up (AI, HSI, GAD 29, GMU 11)?

Jim
 
jliltd said:
While on the subject. I notice that the wiring of the intermediate nodes of the CAN bus is different between the G5 manual and the G3X Touch manual. In the G3X Touch manual, and at the AEA Experimental Avionics class the intermediate nodes show the shields of the CAN pairs connected between the individual can cables and not bonded to the backshells. The G3X manual then shows each end of the CAN bus does bond the shield to the backshell at those two locations only. However, the G5 manual shows every CAN node with the shields always bonded to the backshells, whether at the terminated LRU or any intermediate node.

I have always done it as shown for the G3X. During the AEA class we were told there had been trouble with all nodes being bonded to the backshells and that bonding the shielding to the terminated LRUs only (at the end of the CAN bus) was best.

Now the manuals for the G5 (experimental or STC) show every node bonded to the respective backshell. Is there a preferred configuration on a dual G5 set up (AI, HSI, GAD 29, GMU 11)?

Jim
Click to expand...

Hello Jim,

Both methods should work fine, but our current recommendation for the CAN bus shielding on G3X, G3X Touch, and G5 systems is to ground the CAN wiring shield at the connector shield block on every CAN device.

The folks in our RF testing lab tell us that grounding the shield at each device should have better results and this is required on certified G5 and G3X Touch installations.

The current G3X/G3X Touch installation manual says:
"At minimum, the CAN bus shield should always be grounded to the device connector backshells at the two extreme ends of the bus, but it is acceptable to also ground the shield at any or all other devices on the CAN bus."

Thanks,
Steve
 
Doesn't that introduce a ground loop? In the audio world I believe shields are only supposed to be grounded at one end, the thinking being that if you ground both ends it would most likely introduce a 50/60 Hz hum. But maybe in an aircraft it doesn't matter?
 
AndyWW said:
Doesn't that introduce a ground loop? In the audio world I believe shields are only supposed to be grounded at one end, the thinking being that if you ground both ends it would most likely introduce a 50/60 Hz hum. But maybe in an aircraft it doesn't matter?
Click to expand...

Hello Andy,

You are correct that for audio signals we always only ground the shield on one end at the audio panel.

This is not an audio signal.

Thanks,
Steve
 
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