My blackbox data shows something different but in reality the drone is performing different. 

Acc to blackbox one of the motor is running at 20% capacity while the other 3 are running at 60%. I can see during the test that all motors are running at the same speed almost. 

Is it possible that the data recorded by blackbox might be incorrect??

Fairly uncommon for blackbox to be wrong.

Usually the motor rom is shared back using dshot telemetry and although it may not be ver accurate but the numbers will be in the ball park.

(21-Jul-2022, 11:39 AM)kafie1980 Wrote: Fairly uncommon for blackbox to be wrong.

Usually the motor rom is shared back using dshot telemetry and although it may not be ver accurate but the numbers will be in the ball park.

This is the blackbox flight data

https://easyupload.io/jhsolb


There is huge discrepancy in what is actually happening and what's the FC is recording.

If the FC is receiving information or inferring that one of you motors is running at 20% while the others are running at 60% then you have to chase it down to what is the actual cause.

Is it a mechanical issue? Is is that one of your motors is not running at rated capacity? Could it be a MOSFET issue? Can it be an issue with the motor windings? Or the Motor wires not making a solid connection?

Did you try swapping the bad motor with one of the other good motors to see if the behaviour changes?

(22-Jul-2022, 01:08 AM)kafie1980 Wrote: If the FC is receiving information or inferring that one of you motors is running at 20% while the others are running at 60% then you have to chase it down to what is the actual cause.

Is it a mechanical issue? Is is that one of your motors is not running at rated capacity? Could it be a MOSFET issue? Can it be an issue with the motor windings? Or the Motor wires not making a solid connection?

Did you try swapping the bad motor with one of the other good motors to see if the behaviour changes?

Kafie1980 the issue is not that the motor is running at 20% capacity. I can physically see the motor running at the same capacity as the other motors. The issue is what blackbox is recording. 

Also, during arming is it normal to have P(sum) 4%, R(sum) 5.2% and Y(sum) to 3%. Because I haven't given any input in arming stage in P,R or Y, but somehow there is already have some input. Shouldn't be they stay at 0%?

(22-Jul-2022, 05:28 AM)mohit Wrote: Kafie1980 the issue is not that the motor is running at 20% capacity. I can physically see the motor running at the same capacity as the other motors. The issue is what blackbox is recording. 

Also, during arming is it normal to have P(sum) 4%, R(sum) 5.2% and Y(sum) to 3%. Because I haven't given any input in arming stage in P,R or Y, but somehow there is already have some input. Shouldn't be they stay at 0%?

For a human to see the motors running at the same RPM because an average human can not differentiate more than 60 frames per second. So any thing above 3500 RPM will be very questionable. The motors on FPV quads are in the average 30000-50000 RPM range. Perhaps 10000 RPM at the lower end.

How can we be sure the motors are running at the same capacity?

The only few methods we have that are usable on our quads are:

1- Using a tachometer with reflective tape on the motor bells

2- EMF feedback from the inactive phase in the motor. BLHeli uses this method to estimate RPM.

(22-Jul-2022, 05:51 AM)kafie1980 Wrote: For a human to see the motors running at the same RPM because an average human can not differentiate more than 60 frames per second. So any thing above 3500 RPM will be very questionable. The motors on FPV quads are in the average 30000-50000 RPM range. Perhaps 10000 RPM at the lower end.

How can we be sure the motors are running at the same capacity?

The only few methods we have that are usable on our quads are:

1- Using a tachometer with reflective tape on the motor bells

2- EMF feedback from the inactive phase in the motor. BLHeli uses this method to estimate RPM.

I am not saying when i run it at full throttle. Even when I arm it, it runs all motors at 5.5%, and visually you can tell if any motor is spinning slower or faster. 

But blackbox data shows when armed one motor is running twice as fast as others.