General Electronics & Avionics

[jmorrical]

Andy,

Thanks, that totally cleared the intercom C/B fog. I will removed the C/B and cap the hole.

[jmorrical]

I am building an EX1. I have noticed the Executive Glass Manual shows the CAN bus network with a Can Bus Terminator Block at the GUS 25 ADAHRS. I only have a jumper that splits and connects the magnetometer lead to the two connectors on the ADAHARS. I don't have a terminator.

Is that integrated in the jumper I have or is there something I don't understand?

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[Andy]

I am building an EX1. I have noticed the Executive Glass Manual shows the CAN bus network with a Can Bus Terminator Block at the GUS 25 ADAHRS. I only have a jumper that splits and connects the magnetometer lead to the two connectors on the ADAHARS. I don't have a terminator.

Is that integrated in the jumper I have or is there something I don't understand?

I don't see a magnetometer in the schematic you showed.

I don't know how many ADAHRS/magnetometer configurations CubCrafters has used. On the FX-3 the ADAHRS is in the left wing and the magnetometer is in the right wing. For the EX-3 the ADAHRS is on the avionics tray forward of the instrument panel and the magnetometer is in the right wing. A "jumper" cable seems inappropriate for either of those configurations.

In general terms - Both ends of the CAN Bus backbone must be terminated and there must be no more than two terminators (one at each end). The servos include the terminating resistor and the last servo on the backbone has to have the link fitted that connects the internal terminator. If the last LRU on the backbone doesn't have an internal terminator then you need the terminator block.

The terminator isn't anything fancy. It's just a 120 ohm resistor. (one at each end so any CAN Bus pair should read 60 ohm)

[Andy]

A "jumper" cable seems inappropriate for either of those configurations.

I had not looked at the magnetometer installation recently and had forgotten that the GMU 22 does not have a CAN Bus interface (the later GMU 11 is CAN Bus). The magnetometer should be shown on sheet 1 of your G3X schematic. There are several connector breaks between the GSU and the GMU so perhaps that explains the term "jumper" cable.

There should be a CAN Bus terminator at GSU 25 connector P251.

[jmorrical]

What I say here may not be correct, but what I've come to understanding.

I have spent a good bit of time trying to interpret the Cubcrafters Garmin Manual wiring diagrams that relate to ADAHRS. I think I've figured out that these pages represent an installation of the ADAHRS totally different than our kits. It's the factory build method. My ADHARS is on a tray behind the instrument panel not in the left wing. So, it seems to me some of what's shown related to the ADAHRS is to be disregarded...a matter of confusion for me. I wish there was a note somewhere explaining this or schematics showing how my kit wiring actually connects using this jumper.

Many 'jumpers' are shown in the wiring schematics in the Garmin G3X Installation Manual. Those are not the kind of jumper I've had questions about. This is the jumper I've asked about. I understand this connects the so called magnetometer harness to the ADHARS.

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I think this jumper connects GSU25 ADAHRS to aircraft power, GMU22 magnetometer, OAT probe, GTX335 transponder, GDU465 G3X and the CAN Bus Network. The 9 and 15 pin connectors that fit the GSU 25 ADAHRS are not marked as many are, but they are referenced as...9 pin P251 and the 15 pin P252.

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I'm missing the CAN Bus Terminator Block for the P251 connector that the manual shows. Does anyone have info on this?

[jmorrical]

Kit Support is sending a CAN Bus terminator for the GSU jumper's 9 pin connector (P251).

[jmorrical]

I have noticed the coax connectors at radio and transponder have a bit of play.

All normal?

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[Andy]

I have noticed the coax connectors at radio and transponder have a bit of play.

All normal?

]

BNC connectors are secured by an over-center locking collar that acts on a spring washer. It is normal to be able to rock the connector slightly, or even pull it out a bit, within the compression limits of the spring washer.

it's possible for a badly fitted connector to have the pin pushed back that's a separate issue. As long as the locking collar goes into the over center position, and you have no other symptoms, then don't worry about it.

You'll probably find a mixture of BNC and TNC connectors in the airplane. B for bayonet and T for threaded. TNC connectors won't rock because they don't need the sprung gap for the over-center lock.

[jmorrical]

Andy I'm not sure I stated my question clearly. The connector that is on the back plate each have play without a coax attached.

[Andy]

Andy I'm not sure I stated my question clearly. The connector that is on the back plate each have play without a coax attached.

I have not studied the Garmin trays. However, it is not unusual for tray mounted connectors to have some float so that they align with the LRU when it is inserted. Sometimes one of the connectors is fixed and provides the indexing. Sometimes there are alignment pins and all the connectors float. If everything was fixed the LRU wouldn't fit in the tray unless tolerances were held to zero.