Garmin GSA 28 CAN BUS with an external resistors?

I know that the Garmin GSA 28 autopilot servo has a built in 120 Ohm resistor which is active if I bridge pins 3 & 4. This needs to be done as my Roll servo will be the end of my CAN BUS. Super easy I know.

However, I'm thinking of fitting an external resistor to the CAN BUS here instead of using the inbuilt resistor. I won't put it on the node legs, it will be on the CAN BUS return line like this...



Why? My logic is that it is more resilient. Let's say the GSA 28 has a fault, or the plug becomes disconnected, or someone disconnects the AP servo and forgets to connect the Garmin terminator there, this is all covered by my design. In this scenario my CAN BUS will continue to function.

Question is, will this work? Have I understood it correctly?

If so, will any type of resistor do here?

storkeye said:

I know that the Garmin GSA 28 autopilot servo has a built in 120 Ohm resistor which is active if I bridge pins 3 & 4. This needs to be done as my Roll servo will be the end of my CAN BUS. Super easy I know.

However, I'm thinking of fitting an external resistor to the CAN BUS here instead of using the inbuilt resistor. I won't put it on the node legs, it will be on the CAN BUS return line like this...

Why? My logic is that it is more resilient. Let's say the GSA 28 has a fault, or the plug becomes disconnected, or someone disconnects the AP servo and forgets to connect the Garmin terminator there, this is all covered by my design. In this scenario my CAN BUS will continue to function.

Question is, will this work? Have I understood it correctly?

If so, will any type of resistor do here?

Click to expand...

Hello StorkEye,

Putting a loose component like a resistor in your harness can never be an improvement over putting a jumper between pins 3,4 to activate the termination resistor safely mounted on the PC board inside the servo.

As you say, the servo even comes with a great removal adapter which installs in place of the servo and provides this CAN bus termination in the unlikely event you ever need to remove your servo and fly. The bases are doubly covered without an external resistor.

These connectors probably never fall off, but the knurled thumbscrews do contain holes to safety wire them to keep them from backing out if you are worried about that.

Thanks,
Steve

Thanks Steve, maybe I was over thinking it. I’ll try to find a logical place on the plane to keep the terminator in case I ever need away from home.

PS, I still love the Garmin kit and can’t wait to start on the panel work! ��