Author Topic: Ground loop video noise (Read 428 times)

gavnthat · « **on:** November 11, 2014, 10:07:35 PM »

Got the APM mini and Fpv gear on the teksumo now but added the minimosd and now have noise in the video, I'm pretty sure its a ground loop, the camera and vtx are powered direct from the ESC wires from the battery through an lc filter but the minim is powered from the telemetry port on the APM. The APM is powered from the bec on the current sensor so the ground from the Fpv gear has 2routes back to the battery.
Really what I wanted to check is can I have the 5 volt live for the minim coming from the APM telemetry port and the ground from the lc filter 12 volt feed. This way all the grounds are going one way back to the battery.
It makes sense in my head but just wanted to see what others think before I smoke anything.
The minim would still be getting 5 volt live from the bec and the ground would be direct from battery
I have tested it without the minim osd and the picture is clean.

bigMouse · « **Reply #1 on:** November 11, 2014, 10:36:43 PM »

I can't follow you in detail without a circuit diagram, but instead of thinking ground loops use a ground point where all neg wires are connected to that single point, Obvious best place is neg on the PDB.
Minim should run fine from the apm port, On my old UAV one bec supplies the full apm, gps, data downlink, Rx and a micro servo, whole lot only takes about 200mA

Don't know what minimOSD you have, the early ones worked cooler on dual supplies, later ones fine on one 5v supply

gavnthat · « **Reply #2 on:** November 11, 2014, 10:53:39 PM »

I should have done a diagram really I have the later minim that I have modded so both sides run off the the 5v feed I think this is the problem as it joins the ground to the cam and vtx side. Of minim

MrBen · « **Reply #3 on:** November 12, 2014, 08:20:14 AM »

I only connect video signal on my spanky no ground or power on the video side

gavnthat · « **Reply #4 on:** November 12, 2014, 09:26:21 AM »

Cool that will be nice and easy then

I thought you had to have a ground going in and out the video side toget picture.

gavnthat · « **Reply #5 on:** November 13, 2014, 07:48:18 PM »

Tried running just video in and out the video side of the minim with no ground but the osd flickers and goes off when I throttle up

put it back to how it was, tidied the wiring up a bit and all is good, there is still a ground loop its coming from the current/voltage sensor bec through the apm and minim and into the video loop but the picture is nice and clean now. I will give it a try flying and see if its a problem.