I replaced the AIO that came from my Cinebot30 with a SpeedyBee F4 Mini Stack on my Volador 3" frame. When I hover, it rolls left and pitches back quite significantly. I can see this by just giving a little throttle after arming--the front rises first, and it tilts to the left. All sticks are centered in betaflight, and I calibrated the accelerometer.

I was able to correct this pretty well with the TX trim controls. I then learned about the accelerometer trim settings, and was able to get it to work OK by setting both roll and pitch trim to 50. It's still not quite right, so I'd need to tweak these some more to get it to where it feels OK to fly.

Before doing that, I'd like to figure out why this is happening in the first place, and determine if there's something more fundamental that's not right and that can be fixed. I've never seen this with any other quad so far.

Some more info. I mounted the stack rotated 180 degrees from normal because there wasn't room between the stack and the O3 VTX to fit the capacitor, and I didn't want to use wires to move it elsewhere--there is plenty of room between the stack and the camera in front, so the cap fits nicely there. 



I set Yaw degrees to 180 in BF Board and Sensor Alignment, and of course set my motors order appropriately. All of this works fine, but I mention it in case it might be related to the accelerometer issue.

The other thing I did is flash Bluejay to the ESCs, since they came with BLHeli_S, and I wanted to use RPM filtering. The flashing didn't work smoothly--each ESC got stuck on "resetting", so I had to disconnect and flash again for each ESC, but in the end it seemed to work. All ESCs show the proper Bluejay firmware, and everything seems to work fine except the accelerometer calibration. I was even able to change my startup melody.

Thoughts?

On a related note, I tried to use the Betaflight stick commands to change the accelerometer trims, but it didn't work. The command I used is throttle max, yaw neutral, then either roll right or pitch up to increase the trim settings. The stick command to bring up the betaflight settings in the OSD does work.

(16-Sep-2023, 05:27 PM)aerokam Wrote: On a related note, I tried to use the Betaflight stick commands to change the accelerometer trims, but it didn't work. The command I used is throttle max, yaw neutral, then either roll right or pitch up to increase the trim settings. The stick command to bring up the betaflight settings in the OSD does work.

I was able to fix this. I had raised the throttle stick center to something like 1530, because otherwise I was not able to get throttle max above something like 1964, even with the TX output set to max, and I read somewhere that throttle center didn't matter. I changed center back to 1500, and left throttle max at 1964 (min = 1000). After this, the BF accelerometer trim stick commands work as expected. Now at least I can quickly trim accelerometer pitch and roll in BF to get it to hover reasonably steady, and see how flying feels after that.

Any inputs on how be able to set the throttle stick min, center, max to 1000, 1500, 2000? I played around with offsets in the model inputs page, but couldn't get it to work that way either.

Scroll down to the “Using RxRange to adjust end points” section:
https://oscarliang.com/adjust-tx-channel-mid-end-point/

(16-Sep-2023, 06:52 PM)Lemonyleprosy Wrote: Scroll down to the “Using RxRange to adjust end points” section:
https://oscarliang.com/adjust-tx-channel-mid-end-point/

Right. That's the article that says mid point for throttle doesn't matter:

Quote:Don’t worry about throttle mid point, it’s irrelevant.

At any rate, I went ahead and used the rxrange CLI to set the upper end throttle value correctly (set it to 1966, which then shows 2000 in BF), allowing 1500 to be used as center. It hasn't helped anything.

Before even doing that, the stick commands to trim accelerometer stopped working again. The stick commands to change profiles work--I can see the profile changing in BF as I use the stick command to change it. Not so for the acc trim settings. I don't know what the incantation was to get them working for a bit, but I suspect it has something to do with the max throttle position. I have max throttle set to the default of 1950 in BF.

Since this is a SpeedyBee stack, I am able to use the speedybee app to change BF values, including acc trim. I was doing that in the front yard when motor # 1 stopped working. Brought it in, props off, connected to BF, and all motors were spinning up as expected. Props back on, back outside, and after adjusting the pitch trim a few times, motor #1 stopped again. I also heard a single motor singing the startup tune a few times (at least I think that's what I heard, since it was much quieter than normal), so I assume that was motor #1 acting up.

I see some suspicious motor wire connections to the #1 ESC pads, so I'll fix that and see if it fixes the problem.

Other things that happened during my attempt to get this thing hovering properly. I gave it too much throttle yesterday at a local school, it shot up in the air, I disarmed, and when it crashed the bell and prop from a motor were missing. I think it was motor #2. It occurred to me that maybe the bell wasn't properly secured to the rotor, and maybe that had been causing the acc. problem, but after replacing the bell and the prop, same acc. issue.

Today I also noticed some non-zero values in the board alignment section for roll and pitch. I have no idea how that came to be, but I thought maybe that had been causing the acc. issue. Nope. Set them to 0, and it's still pitching back as soon as I give it enough throttle for any part of the quad to lift off.

I'm still curious to know if anyone else has ever had a quad that pitches and rolls so much with sticks centered after calibrating the accelerometer. I hadn't seen that in any of the three quads I've built. I'm wondering if the FC is faulty, or if it's related to rotating it 180 degrees for the installation.

As long as you correctly set board alignment, as it sounds like you have, rotating the fc wouldn’t cause that.

I have had quads veer wildly on takeoff, but it’s been my fault and was caused by a “drunk” gyro. Gyros are electromechanical, they’ve got tiny little moving bits in there. If you crash too hard or too often, it can damage those bits or cause them to get caught up. Usually a good smack onto concrete will free it up and allow me to get more flights in until I’m in the mood to do hot air work and replace the gyro.

In your case, since you haven’t mentioned repeatedly cratering this thing in the ground, I might suspect a faulty gyro/accelerometer from the factory. You can verify or rule that out via the sensors tab.

I redid two of the motor 1 connections, and not only did this get the motor working , it solved the acc. problem! So I guess the motor connection was intermittent, and the motor 1 was never working at 100%, causing the drift.