Hi all,

Over the weekend I finished building my second quad (a clone of my first build to act as a backup). The original quad is built with the exact same components and can run 3S and 4S fine. But the new quad constantly rebooted itself when using 4S.

Before I go too far into detail, I have found and fixed the issue! but I was looking for advise on if what I did to fix the issue is correct or there is a better way to do it.

The problem was the flight controller which is a Omnibus F4 from banggood, the 5v regulator was being overloaded when using 4S and the board was rebooting. On my original build I had the full voltage of the battery running to the vbat pin and besides the OSD and receiver, nothing else was being powered from the FC.

To fix the issue I ran 5v from my PDB to the vbat pin on the FC, this of course caused me to lose correct voltage info in my OSD, so I ran a wire from the VCC pin on my PDB to the vbat pin on my runcam swift 2 and am using its OSD to display my voltage.

My question is, should i be running my FC off 5v through the vbat pin (which still goes through its own 5v regulator), or should i remove the 5v regulator from the board and run the 5v to one of the 5v motor pins to power the board. Essentially my FC is being powered through 2x regulators... is this an issue? And if not should I update my original build to the same to reduce stress on that regulator?

Thanks! and let me know if you need more info.

If your setups are the same, and your soldering is OK everywhere, then you possibly have a faulty FC. Instead of changing the one that works fine, you might consider documenting and contacting BG for a replacement FC for the one that doesn't. They're usually pretty good as long as you have a video or photos of the issue. Why mess with something that isn't working like it should? My 2 cents...

(10-Jul-2017, 11:07 AM)sloscotty Wrote: If your setups are the same, and your soldering is OK everywhere, then you possibly have a faulty FC.  Instead of changing the one that works fine, you might consider documenting and contacting BG for a replacement FC for the one that doesn't.  They're usually pretty good as long as you have a video or photos of the issue.  Why mess with something that isn't working like it should?  My 2 cents...

Thanks sloscotty, good point, I will do this.

For anyone wondering about regulators in future though, I found that with an input voltage of 5v the FC's regulator was outputting only about 3.3V (it was working but this was too low). To get it working at a more reliable voltage I switched the input voltage to a 12v output from my PDB, now the regulator is putting out 5v correctly and everything seams stable on 4S. But I would still consider my board faulty and will be seeking a replacement.

UPDATE: Don't do what I did here, see Oscar's post below

Hi!

I'm using similar FC (the one without integrated OSD). I run my system on 4S.

Even without any other components - only the FC pcb - that 5V regulator gets extremely hot (around 85-90C, measured with IR camera). I wouldn't connect anything else behind that regulator. The first build of yours must be at it's very limit and would probably fail on hot days.

This is what I did to get everything working on my quad (including the voltage measurement):

1. I disabled the on-board 5V regulator - instead of completely removing (de-soldering) the regulator, I just cut through one of the regulator's legs - the input pin.
2. I connected another wire from PDB's 5V rail to one of the FC board's 5V pin to power the FC.
3. I connected the VCC (battery voltage ~16V) to FC's VBAT pin - FC can now measure correct battery voltage (the on-board 5V regulator is not needed; the VCC wire is only used for FC voltage measurement).

And that's it.

DO NOT power your FC with 2 voltage regulators..
There is a chance that you could fry one of the regulator or both if there is a voltage difference, and they don't have reverse current protective circuits in them.

(10-Jul-2017, 01:40 PM)rapidsh0t Wrote: Hi!

I'm using similar FC (the one without integrated OSD). I run my system on 4S.

Even without any other components - only the FC pcb - that 5V regulator gets extremely hot (around 85-90C, measured with IR camera). I wouldn't connect anything else behind that regulator. The first build of yours must be at it's very limit and would probably fail on hot days.

This is what I did to get everything working on my quad (including the voltage measurement):

1. I disabled the on-board 5V regulator - instead of completely removing (de-soldering) the regulator, I just cut through one of the regulator's legs - the input pin.
2. I connected another wire from PDB's 5V rail to one of the FC board's 5V pin to power the FC.
3. I connected the VCC (battery voltage ~16V) to FC's VBAT pin - FC can now measure correct battery voltage (the on-board 5V regulator is not needed; the VCC wire is only used for FC voltage measurement).

And that's it.

Decided to give this method a try, clipped the legs off the FC's regulator and ran 5v and GND from my PDB to the 4th motor 5v and GND to power my FC. Ran VCC to FC Vbat pin and all is working perfectly! The board is running from the 5v and I'm still getting betaflight voltage. This has been a good learning experience.

(10-Jul-2017, 02:09 PM)Oscar Wrote: DO NOT power your FC with 2 voltage regulators.. 
There is a chance that you could fry one of the regulator or both if there is a voltage difference, and they don't have reverse current protective circuits in them.

Thanks Oscar! This is really good to know. Luckily I didn't have an issue in the 2 test flights I did with this setup. I've taken the FC regulator out of the equation now as above.