Trimming the yaw

[gicks]

Hi everyone,
Yesterday I had the first flight of my first quadcopter and I was amazed with the stability using the standard PID settings. I was expecting to do a lot of calibrating and messing with PID settings, but the copter is stable already! (flying gyro, WMP only)
With a bit of trimming on the transmitter the roll and pitch drift is eliminated and the quad hovers in place nicely. The YAW axis however needed more trimming, so much that I could not arm the quad anymore.

The multwii FAQ also mentions this problem, but not the solution.:

The motors start & stop but after trimming the yaw it’s no longer possible to start or stop the motors
By setting the trim, the complete range moves up or down so the endpoint does not reach the desired 1000 or 2000 any more.
One transmitter suffering from this is e.g. the very basic Planet T5 2.4Ghz transmitter.

I am using a simple transmitter, Spektrum DX5e, and cannot adjust endpoints or traveladjust to 120-140%. Instead I changed the values MINCHECK and MAXCHECK to respectively 1120 and 1870.
What is the best solution to trim the tendency of clockwise turning on the YAW axis? Is it possible to do this in the code?
Or should I just adjust the MINCHECK en MAXCHECK even more, so I can arm the copter even after trimming the YAW?

Additional set-up information:

Motor: EMAX FC 2822
Propellor: 8x4.5 flyduino
esc: Hobbyking 18-20
battery: zippy 3000 mAh
transmitter: Spektrum dx5e
receiver: OrangeRx R710

Gyro: WMP
arduino: Nano V3.0
DIY frame, total weight 1009 gram

[PatrikE]

Check in the gui if your channels center at 1500.
If not it can create a drift in all axis.
There's a parameter MIDRC to adjust if needed.
But its general and aplys to all channels.

[gicks]

Hi,

This is a picture of what the MWC GUI shows me. I have all trims on transmitter set in middle position.



Since I am using 1120 and 1870 instead of 1000 to 2000, should I change this MIDRC parameter to ((1870-1120)/2)+1120= 1495?

[tovrin]

also, you can use roll to arm/disarm as long as throttle is at minimum, instead of yaw.

[chris ables]

I have heard of yaw gyro reversed causing this !

[gicks]

also, you can use roll to arm/disarm as long as throttle is at minimum, instead of yaw.

Thanks tovrin, great tip, this solves the problem of arming the copter after trimming the yaw.

I have heard of yaw gyro reversed causing this !

Actually when I tried the first few hops with the MWC I noticed that YAW, ROLL needed to be reversed. I first tried reversing YAW using the piece of code in the config.h file., but this resulted in a quadcopter spinning fast around the yaw axis without any stick input. So I decided to reverse the YAW and ROLL using the sliders on the transmitter.

Thank you everyone for your input. I should be able to now trim the yaw and still arm the quad.

Still would like to know about the MIDRC parameter. Since I am using 1120 MINCHECK and 1870 MAXCHECK instead of 1100 to 1900, should I change this MIDRC parameter to ((1870-1120)/2)+1120= 1495?