VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 12-19-2017, 02:37 AM
storkeye storkeye is offline
 
Join Date: May 2015
Location: Aylesbury, UK
Posts: 10
Default 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?
Reply With Quote
  #2  
Old 12-19-2017, 05:24 AM
g3xpert's Avatar
g3xpert g3xpert is offline
 
Join Date: Sep 2010
Location: Olathe, KS
Posts: 1,955
Post

Quote:
Originally Posted by storkeye View Post
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?
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
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.

Last edited by g3xpert : 12-19-2017 at 05:27 AM.
Reply With Quote
  #3  
Old 12-19-2017, 06:39 AM
storkeye storkeye is offline
 
Join Date: May 2015
Location: Aylesbury, UK
Posts: 10
Default

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! ��
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:11 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.