Kosmik / JLog / Jeti Rx - avoiding a ground loop

[jmackey]

In the diagram below, the JLog gets power (5v) from the Kosmik option port and telemetry data is sent to Jeti receiver EX port with (+) removed. Jeti Rx is powered through single line UDI connection to VBar NEO, that is powered by Kosmik BEC master / slave connections at 8v and R2 buffer.

Is there any risk of ground loop between receiver and JLog with just the (+) wire pinned out on that connection?

Or would it be safer to remove the (-) as well, leaving only the signal wire between receiver and JLog?

Nothing to do with JLog, but I'm a little paranoid after 4 incidents of lost of control and 2 bad Goblin 700 crashes. After eliminating everything else, the best explanation for these incidents is a ground loop created by my wiring power to receiver and also Spirit FBL, and single line EX Bus between them to complete the ground loop (un-knowingly of course). Full post here if you are curious
https://www.helifreak.com/showthread...=712741&page=7

Also, The 2 helis in those 4 loss of control incidents each had different JLog 2.6's wired as above (+ removed between JLog and Rx EX port). 1st JLog was melted in the crash & burn...


Thanks,
Jay

[dl7uae]

Looks good so far..

Has nothing to do with ground loop: Better to supply JLog not from KOSMIK's options port than from receiver or anywhere else at the output of the BEC.
Cut the (+) wire in the KOSMIK harness. Put the red (x) wire from telemetry cable at JLog's end on the inner pin of JLog's "JIVE port" (where else is "signal"). That's better because of the BEC integration design bug. Voltage can go crazy at power up.

On the other hand the BEC output voltage does the same (as the 5V coming out of the options port). AND: The charge current into the buffer can provoke the BEC bug directly to appear (during the 1st 10ms after power up, - may last then infinitely (sawtooth oscillation)). Would be better to have an Opti BEC Guard between BEC output and everything else, including the buffer. In that case the (+) wire in the KOSMIK harness have to be cut anyway and JLog supplied from its "JIVE port" - to avoid a bypass.
Use a single BEC Guard (master/slave soldered to its input) or just two.




A ground loop could be build by that damned master/slave (depends on how it is applied). Running both into FBL looks good.
Another reason for a ground loop could be the ground wire in the KOSMIK harness. Nevertheless, I do not see a reason yet to cut this wire.