[Resolved] No throttle control on arducopter 2.9.1, quadcopter 3DR, APM2.5

Update 19/02/2013: problem has been resolved. See discussions below for conclusion.

I am in a dead end that frustrates me to the point I might give up soon...any help welcome.
I have not yet flown my new quad that I try to finalize for weeks now,learning step by step how to solve the hidden road blocks. Except this time I am at a road block I can't resolve and do not find any info on the wiki.
This is the issue:
-I am at the stage where I have apparently succesfully calibrated the ESCs until step 6 of the wiki automatic calibration procedure
-After that if i turn on the quadcopter again and I arm it with the throttle stick bottom right for 4 seconds,then comes the issue:
Any throttle stick position make the four motors turn at a constant speed (except full down where motors stop). It is as if the throttle stick would be an on/off switch.
If i connect one esc directly to channel 3 of the receiver,then stick works as expected.
So is it a defect on my APM board,not able to send variable pulses to the output rail? is it a problem with 2.9.1?
(i was in stabilize mode)

Any advice/ help please!

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I've been in RC since 1980, electrics since they first came out, and Arducopter since about three years back.

And I say calibrate your ESC's one by one using the correct battery, and straight out of the throttle port on your RX.

Once you KNOW the ESC's are working, you can start to fault find the rest of the system.

And sometimes you have to do the APM upload/config/radio calibration a few times before it works properly.

Yes, I do electronic repairs/fault finding for a local RC supplier/ Drone supplier :-)

I will try your suggestion to calibrate the ESCs one by one (i did not try that yet), howeverI am pretty sure they are correctly calibrated. I can for example see in the mission planner the display of the following parameters : CH3 IN and CH3 OUT.

CH3 IN varies correctly in function of the position of my throttle stick (low PWM value 989- High PWM value 2013)

but CH3 OUT is either PWM 989 when stick full down, or PWM 1700 whatever the stick position. This means that the APM does not translate/forward correctly the CH3 value from the receiver to the motors control wire. It is as if the APM would output on CH3 OUT a fixed value of 1700 PWM...

It is also as if after I unplug the battery at step 6 of the end of ESC calibration, the APM does not "memorize" the parameters. Because as long as I stay on step 6 without unplugging the battery, everything works perfect and in function of the throttle's stick position.

Hope I do not have a defect APM board...


     Of course you're testing in stabilize mode right?

     If you can see those values in the mission planner then it means that arducopter is trying to output those values.

     Not that is should matter but you have a very wide throttle range (989 ~ 2013).  In fact, ESCs only have 800 positions (i.e. something like 1100 ~ 1900) so there's no advantage to having a wider range than that.

     Maybe you can make video?

Yes indeed I am in stabilize mode (i see I have the checkbox "simple" ticked next to the flight mode in the mission planner, does that matter ?).

I will make a video of my problem. I indeed see those PWM values in the mission planner. I am using as Tx a classical Turnigy 9x with ERX firmware, so nothing special in principle.


So I have done the following :

-I have calibrated the ESCs manually , one by one , succesfully: with direct connection between ESC and receiver, I get a normal throttle control (input=output PWM).

- I have reconnected all 4 ESCs to the quadcopter, redone radio calibration. I can arm without problem and I am in stabilize mode.

But still same problem. I illustrate with pictures:

First picture: motors are armed, throttle stick full down : ch3 in->PWM =989, Ch3 out->PWM=989


On the second picture I push the throttle stick at about 50% : ch3in->PWM=1633, ch3out->PWM=1119

On the third picture : I push throttle stick at maximum : ch3in->PWM=2012; ch3out->PWM=1267

In addition I notice that leaving the throttle at same position, the ch3out varies between 1200 and 1400 in a kind of random way (ch3in stays constant).


Is this normal or do I have a problem with the arducopter code/APM ?

I don't know if this helps, but I'm having what could be a similar problem using APM 2.5 and 2.9.1 on my DJI450 quad.  I started describing it in the comments on this posting:


The two differences are (1) I'm using ESCs that cannot be calibrated (the DJI Opto 30 model), and (2) instead of getting a fixed throttle response, I get no throttle response (which is like saying mine is fixed at 0).

It'll be interesting to see if this is really just two versions of the same problem.  I'm currently at a loss for what else to try.

I am more and more leaning toward a problem with 2.9.1.

I had 2.8.1 and do not remember having this issue. Maybe a good test to try reload 2.8.1 ?

Interesting... that totally seems worth trying. :-)

This my first quad with APM and I started with 2.9.1.  (Pervious builds were KK2 boards.)

Would be nice to know if 2.8.1 has same issue or not. Please post your results. I won't be able to test that myself for the coming week but I will afterwards.

Ok, I'll try this weekend.

heelo Randy, can you take a look at my last post in this thread with the pictures I posted. I even tried tonight with 2.8.1, same behaviour. I do not understand why the APM outputs constant PWM values to the four motor control lines whatever the throttle input value. This drives me nuts !

Hello,I just tried now with 2.8.1, same issue for me.

Still stuck without a solution.. lets' hope someone has an idea.


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