Feather

By painfpv on Jul 27, 2020

3  128  8

whenever I force a current spike (very quick rolls, very quick punch with full lipo) the image goes dark for a fraction of a second. I can also see the OSD overlay quickly dissapearing and apearring again when the image goes black. when I fly it with a small lipo (450, 650mah) it generally flies good and its hard to force the above issue. with a fully charged 850mah though lipo the issue occurs imediatelly. any small but quick touch throttle input forces the video issue.

Update: with proper caps it flies perfectly fine even with a fresh 850mAh pack. (no longer valid: also on a fully charged 850mah pack, besides the image issue, you can also hear an oscilation noise in the motors similar to the issues reported by kebabfpv with his ultralight AIO setup.)

see the video problem in the video at 00:03

Photos

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Dash   14 days ago  

I ended up here as I'm scoping out parts for a ET5 and I'm curious about these BH 2004's in 3150Kv.. but I noticed your video and black screen issue and it aligns with some concerns I have using these motors within the lightweight 5 incher realm (sub-1000mah, sub-250g AUW, 5125 and similar props)
See the specs on pyrodrone or wherever.. on 4s and a 5125 prop these motors suck 32 amps each, thats 128 amps total on a straight up moon shot.
Problem is, a 100c 850mah is only good for ~85 amps continuous, maybe a bit more new. A older 75c 850 will be lucky to hit 60 amps, which is less than half of what these motors will try to pull at 100%

With all that said - In your video I don't see a large voltage sag or amp draw before or after the black flicker. Looks like it might be 37 amps total??
I'd say its an issue on or within your FC as the osd is missing from several frames while the cam and vtx are humming along fine.
It looks like the osd resets and interrupts the Video in/out, then takes a second to display again, meanwhile the cam and vtx are still working without osd info.

Try tying it down to a workbench or clamp it into a vice and see if you can duplicate the issue with throttle alone.

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Dash   12 days ago 

Bummer..
The problem has to be in the OSD/FC itself - if it were in the cam the osd would overlay a black screen, if it were in the vtx it wouldn't show a few frames of video without the osd text. The video in/out is simply being interrupted.
Good news is your Pheonix 2 should have its own configurable OSD. Power the cam directly off of VBAT and it'll display pack voltage, and I think it has a timer too... but you're on you're own for rssi :/

btw.. your using the same AIO I'm considering (maybe not now lol) what BF version are you using, how are the pids/filters, and do you run RPM filtering?

Thanks

painfpv   12 days ago 

nice idea to use the camera OSD but I am not sure my camera has this feature, I have to check. I am running phoenix 2 nano version (contrary to the build description where by mistake I didn't mention it was the nano version).

I tried tunning the crap out of the ESCs. played with PWM frequency, ramp up and demag while trying to mitigate spikes. I took rampup down to minimum to see the OSD issue disappears (it didn't). I went to max PWM frequency to see if there is any significant difference (none that I could feel).

I am using BF4.2 with default settings and no RPM filtering. it flies so good that I don't feel the need to change anything. I will post a video to show how it flies after I bypass the OSD.

Dash   12 days ago 

Are you using RMP filtering? (its blheli_32 right?)
Either way, BF 3.5.7 is pretty good on lightweights - maybe do a CLI dump of your 4.2, then backdate it to 3.5.7... there might be some hiccup in 4.2 that's causing your issue.
It only takes 3 minutes to reload 4.2 and past your dump back in...

You might just have a sketch board with a crap regulator (shrug)

I'm definitely curious tho... was planning the exact same build with a Vista.
I might skip the AIO's altogether and use a F7 20x20 stack... same price, far better filtering (more caps), larger pads, and if either part poofs I spend half as much fixing it.
But I'm not sure if it'll all fit under a PHX-3d HD canopy without a bunch of janky weak standoffs?

Jodie Froster   16 days ago  

Oscillations could be from that vTx antenna waggilin' round. Perhaps a different length antenna, or a canopy that has a cool spot for it.
You might have a harmonic that builds at a certain frequency that you just NAIL at max throttle, or close to it. Maybe reduce your max throttle % by 3 or 4 (you won't miss the power. Really.).
Maybe get into blackbox? It's an interesting side of the hobby :)

painfpv   16 days ago 

I wish you were right but the problem is clearly an electrical one. The image goes black for a second, meaning that a spike reaches the OSD, Cam or VTX.

painfpv   16 days ago 

I've added a small video in the description

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