Welcome to DroneRacingPilots!
Join our free drone racing community today!
Sign up

My flight controller works under usb power but not battery power, however my vtx works with battery power while wired through my flight controller

stoem

New Member
Joined
Aug 12, 2020
Messages
4
Reaction score
0
Age
18
I just built my first drone and 5 seconds after I took off it completely shut down then rebooted with only the vtx working. So far I've figured out that my receiver is broken. But my flight controller is in a very situational issue. It does not power up when plugged into my lipo battery, but the vtx still works and transmits a signal (just a black screen). But when I plug my fc into my computer it powers up and the LEDs go on and it operates in betaflight as normal. I've that it is usually that a fc will not work under battery or USB power, but for me it still gets power properly just only to the vtx. When the USB and battery are in the camera works fine but the moment I unplug the USB cable the camera no longer works and the LEDs on the fc go out, but the vtx is stable. I'm hoping someone on here is able to help me find the cause of this and what I can do to resolve this issue.
 

HighTechPauper

Well-Known Member
Joined
Feb 5, 2017
Messages
2,548
Reaction score
2,968
Location
The Chesapeake Bay
It all depends on what voltages things are connected to, in all likelihood you have a fried 5v regulator on the FC.
What voltage is feeding the vTX? Something other than 5v?
What voltage is feeding the cam? Assuming camera is hooked to 5v
 
  • Like
Reactions: stoem

stoem

New Member
Joined
Aug 12, 2020
Messages
4
Reaction score
0
Age
18
It all depends on what voltages things are connected to, in all likelihood you have a fried 5v regulator on the FC.
What voltage is feeding the vTX? Something other than 5v?
What voltage is feeding the cam? Assuming camera is hooked to 5v
So my vtx was connected to 9v and I just plugged it in again and now the vtx doesn't power on or transmit a signal anymore. The camera was also a 9v pad, the receiver was a 5v/3.3v pad where I had to make a solder bridge on the bottom of the board to select a 5v output, so it was a 5v pad. I'm not sure what happened to my vtx just now because last night it was working as usual but when I plugged in today it didn't work at all. I have a 4in1 esc below my fc that is connected to my battery as well. I also tested the pads with a multimeter and they read the correct 9 and 5 volts.
Edit: vtx is probably fine the ground wire became disconnected from the FC.
Edit 2: after some thinking I think there is something wrong with the 5v regulator, as you mentioned, because my camera gets warm on the lipo, so I think its getting power. And it might not transmit to the vtx because the fc is unable to take that video input, put the osd over it and send it out to the vtx. So what can I do about fixing the 5v regulator.
 
Last edited:

HighTechPauper

Well-Known Member
Joined
Feb 5, 2017
Messages
2,548
Reaction score
2,968
Location
The Chesapeake Bay
My guess is that the FC's voltage regulators/power circuits have completely blown now. Powering up anything is when the greatest "shock" to the system occurs, if you ever walked into a room and flipped the light switch and the light starts to come on, and then blows, you have seen that power surge shock in action. So it looks like the 5v circuit that steps down battery voltage was bad, and when you fed it 5v from the USB side things would work, and plugging in the battery still had the 9v so the cam and the vTX were likely working but when the FC didn't have the 5v needed to run the OSD and allow the picture through the FC, you had your black screen. Now I think both power rails are gone on the FC and your going to need to either replace it or add an external vReg to replace the 5v and 9v power to the board which could still go at any time due to previous damage. I think you need to replace the FC.

That being said, since the FC is connected to the ESC, it still all depends on a few things, like does the 5v come off the ESC to the FC, or does the FC supply vBat to a 5v vReg on the FC? It could still all be a bad set of V/Ground wires (5v or vBat, whichever) connecting the 2 boards, and especially if it is connectors instead of soldered on wires on both sides.
 

stoem

New Member
Joined
Aug 12, 2020
Messages
4
Reaction score
0
Age
18
My guess is that the FC's voltage regulators/power circuits have completely blown now. Powering up anything is when the greatest "shock" to the system occurs, if you ever walked into a room and flipped the light switch and the light starts to come on, and then blows, you have seen that power surge shock in action. So it looks like the 5v circuit that steps down battery voltage was bad, and when you fed it 5v from the USB side things would work, and plugging in the battery still had the 9v so the cam and the vTX were likely working but when the FC didn't have the 5v needed to run the OSD and allow the picture through the FC, you had your black screen. Now I think both power rails are gone on the FC and your going to need to either replace it or add an external vReg to replace the 5v and 9v power to the board which could still go at any time due to previous damage. I think you need to replace the FC.

That being said, since the FC is connected to the ESC, it still all depends on a few things, like does the 5v come off the ESC to the FC, or does the FC supply vBat to a 5v vReg on the FC? It could still all be a bad set of V/Ground wires (5v or vBat, whichever) connecting the 2 boards, and especially if it is connectors instead of soldered on wires on both sides.
I have the JB f4 AIO FC and the JB 4in1 esc, if that helps at all. But yes the fc is fed vbat and I think it steps down to 5v to power the fc itself. But if the 5v pad is reading 5v does that mean that it is completely blown? I also tried connecting the battery directly to the fc and that did not power it up so it probably isn't the ground wire.
 

HighTechPauper

Well-Known Member
Joined
Feb 5, 2017
Messages
2,548
Reaction score
2,968
Location
The Chesapeake Bay
There have been a number of revs to those boards, the FC has been known to have weak 5v and 9v regs and not sure if that has been significantly improved though I know they have tried. So what you are telling me is that with ONLY the battery connected you have 5v, if so then it sounds like maybe it isn't the 5v rail and something else has broken.
 

stoem

New Member
Joined
Aug 12, 2020
Messages
4
Reaction score
0
Age
18
There have been a number of revs to those boards, the FC has been known to have weak 5v and 9v regs and not sure if that has been significantly improved though I know they have tried. So what you are telling me is that with ONLY the battery connected you have 5v, if so then it sounds like maybe it isn't the 5v rail and something else has broken.
I may have misspoke, with the battery plugged in my multimeter reads 5v on the 5v pad and 9v on the 9v pad. So the power is being given to the parts but not the chips on the fc, or something like that. The power is there on the pads just not for the fc. There’s something I heard about called a diode and there one on the bottom of my board that gives 5v or something like that. I tested the legs on the diode and there was continuity from the multimeter on one leg between the leg and the usb plug but there was not continuity between the other leg and the voltage input from either the battery+ pad or the voltage input on the pin connector to the esc. Maybe that is some more information on a possible fix.
 

HighTechPauper

Well-Known Member
Joined
Feb 5, 2017
Messages
2,548
Reaction score
2,968
Location
The Chesapeake Bay
Sorry for the late reply, been pretty busy the last few days.
There is a number of issues trying to fix these small boards, but you are welcome to try if you want.
No schematics to troubleshoot with even if you did have an O'scope and the other skills and knowledge to accurately troubleshoot.
The parts needed to fix these boards are hard to find in any small quantity, are very expensive by the time you add shipping costs, and SMD soldering requires special tools and skills to do the job effectively.
If you are indeed looking at a diode, the basic principle of a diode is like a check valve, it allows current to flow in 1 direction, but not the other. There are some used for voltage regulation that work in reverse bias at the "avalanche point" called a Zener diode, but either way I don't think repair attempts are cost effective compared to buying a new board.
If you do indeed have voltage, then it seems something else has blown on the board or the BF code on it has been corrupted or lost, it could even be that the CPU is toast.
 

Latest threads

Members online

Forum statistics

Threads
3,437
Messages
29,527
Members
2,917
Latest member
Shylz