Unexpected motor glitches (speed up) with Tri Hex and Octo APM 2 & APM 2.5 using 2.73

It seems since going to 2.7 and up to 2.73 I am having uncontrollable glitches with the motors. I think I have isolated everything, no bullet connectors, checked the amperage draw of the 880 motors to see if bearings could be the problem.
I have 2 units, TriHex & Octo with 1 inch carbon fiber tubing for the arms, exhibiting the same glitches, I don't know what's causing it. This morning I flew the TriHex for about 10 seconds and about 5 feet high and suddenly it rolled completely over upside down all within less than a second and broke 5 props, anybody else having this problem or a solution. I'm not flying anymore until I have a fix.....I see 2.74 is in the works but don't see anything that would fix this....Don

Views: 3840

Reply to This

Replies to This Discussion

I have the DX8 TX and the AR8000 RX.
In my case which sounds like yours, the motors would pulse. I could clearly hear the motors increase in speed.
Are you saying the issue is ch 6 or ch 6 & 7 connected?


You do use the same setup.
The issue is only when I hook up aux3 to either ch6 or ch7 and only if aux3 is set to maximum.
If you don't connect aux3 it works without any problem.
Last test I did was aux1 - ch6, aux2 - ch7, aux3 unconnected at maximum --> no issue.

For the moment I can't see why this is happening but I guess I need a good night sleep.
Maybe it will be more clear tomorrow :-)

I had a look into the logs...
First part is with aux3 set to minimum.
At line number 1400 I turned aux3 to maximum and the motor spikes appear.

Around 2200 I cut the throttle and set aux3 back to minimum, throttle up --> no spikes

When I had the problem, it was spiking without the batteries connected also.
Does it spike on the bench, no power to the ESC?


The graph I made was on the bench with only RX and USB plugged in (no external power or motor connected).
I just did a test by mixing aux3 onto aux2 in the DX8 via the Mix switch.
This works, so connected aux2 (AR8000) to ch6, flipped the mix switch to 'on' and aux3 now outputs via aux2 --> no glitches.

This can be used as a workaround until someone can fix the problem permanently.

Sounds like you have something here, would this be the same with the Futaba system, I have a FGH 12


Unfortunately I can't verify this as I only have Spektrum.
I would give it a try by connecting up to eight channels.
My wild guess is that something is not quite right with the last channel conversion in the code.
But again it is a wild guess as I need to have a look into the code myself.
I've been busy detecting the cause and finding a workaround.
Next will be a dive into the code.

Thanks Jan, I hope you can figure it out.


We just fixed our own motor glitches and twitches problem after some time. The culprit was the multi-connector cable between receiver and APM board. They were probably a bit worn and if there is some vibration, they loose contact. An observation though, this same connector works well with the AQ50D FC. Possibly, less filtering of input noise/glitches or more noise sensitive inputs in the APM. Hope this helps those who are having the same problem. 



Thanks, not sure this is my problem as I have a tri-copter and also a quad doing this with an APM 2 and the other with an APM 2.5 doing it, but I will replace as I have an extra connector.
Jan, so then is the problem with channel 6, which I use for the camera stabilization, and if I were to disable that function I should not have any glitches if I understand correctly.


Not quite, at least not in my case.
For the moment I use ch6 and ch7 and the quad is airborn without any glitch, it flies very smooth even with stock PIDs.
I only did not connect aux3 of my AR8000 which is the last channel of my DX8.

my current setup:

ch1 to 5 -> standard

ch6 - aux2 (AR8000) that is mixed to aux3 so I can use the knob on the DX8 to tune my parameters

ch7 - aux1 (AR8000)

--> No issues here

My findings, at least with a DX8 and AR8000 is that as soon as you connect aux3 to either ch6 or ch7 and put aux3 to maximum the glitches appear. I've been able to reproduce this several times.

If I'm correct you have a Futaba with at least 8 channels.
What would be interesting is to see what happens if you only connect 7 channels and next if you connect 8 channels.
How is your current setup on receiver level?

Reply to Discussion


© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service