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Quad Question: Constantly re-trimming the Transmitter with the Flight Contoller?

#1
Hey There!

I've been building/flying quads for about 6 months now, but I haven't been able to find an answer about trimming.

I'm using a KK2.1.5 board (old, I know) with a Spektrum DX6 (SPM6700). Every time I go out to fly, I have to go the the receiver test screen and re-trim (through sub-trims) so that everything zeros out.

People mention setting the sub-trims when setting up the KK2, but no one ever seems to mention if trimming is a one time thing or if that is expected each time you go out to fly.

So my questions are:

Is re-trimming each time you fly to be expected?
Is that just a fault with the KK2.1.5 board?
Should I expect to constantly re-trim with any future flight controller that I buy?
Are there additional settings on the transmitter that I am missing?

Any guidance would be much appreciated!
 

ElectriSean

Eternal Student
Mentor
#2
Once you set your centers you should never have to touch the trims again. If they are moving around a lot, it's a problem with your transmitter - the FC and Rx just take the values they're given.
 

PsyBorg

Wake up! Time to fly!
#3
Did you calibrate the KK2 on a level surface? Are you giving the FC enough time to stabilize before flying? How worn are your gimbals on your radio is it old? If all of that is good check and make sure the physical trims on your radio are centered before setting sub trims. Its very easy to unknowingly bump those while whipping the sticks around. NEVER touch those to trim the quad. Always set centers and endpoints in software.

Finally when you have to trim is it always in the same axis? If so then look for issues like bent shafts or binding on any motors that effect that axis. Then recheck how you mounted the KK2. Is it parallel with the frame and not leaning to one specific side? Is it loose and can move from vibration or tilting?
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#4
so . . . I'm wondering . . .

How's the weather been up in your part of Indiana?

Flying outside? Pretty cold this time of year? (listen to me talk -- it's a nippy 60°F outside my door :eek:)

Maybe dragging a warm copter and TX out into the harsher elements?

There's been quite a few reports of servos drifting in the cold (bring a warm tower-pro 9g servo outside and you can watch it "recenter" as it chills) I haven't seen an RX/TX do that before . . . but first time for everything . . .
 

PsyBorg

Wake up! Time to fly!
#5
I live dead smack in the middle of New York which can get or be as cold during winter. I have flown a skyline32, a spf3 clone and now a Kiss fc in weather below freezing and never had a drift problem I have noticed. Early in my time flying quads I was even dedicated (stupid) enough to fly in windchill's below zero a few times before I knew the stress on batteries. Servos I would think struggle even more under certain temps as I believe the lithium grease used in them is not temp sensitive and could even potentially freeze to near solid.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#6
True . . . but have you ever flown it with a KK2.1.5?

There actually was an electronics issue (not sure if it was fixed) in the TowerPro 9g servos drifting as the servo cold-soaked -- chill the chips, and the clock slowed down . . . and 1500ms to a sluggish freezing servo controller starts looking more like 1550 . . . or 1600 . . .or 1700 . . . someone here posted a freezer experiment they ran after isolating the issue a few years back.

I've never had a drift issue with any of the kk2.x boards I've flown but I don't get much cold soak in Middle Georgia (current late afternoon temp: 64°F -- it's getting chilly out there), so not seeing an obvious source of the headache, knowing the time of year, location and the potential for cheap electronics to have trouble keeping time as they chill . . . it's worth looking into.
 
#7
Yes, the KK2 was definitely calibrated on a level surface.

After powering on the FC, I always check the "Receiver Test" screen about 10 to 20 seconds after powering up. (Then I see it's not zeroing out). I correct that with sub trims and then fly.

If I remember correctly, I calibrated it before I set the trims. Should I set the trims before calibration?

The FC is stable and parallel to the frame.

The funny thing is, I have the same problem on another quad with another KK2. So I know it's not the specific FC. I use the same TX with both. The transmitter is basically brand new. I got it in July but probably haven't logged 6 hours on it yet.

Did you calibrate the KK2 on a level surface? Are you giving the FC enough time to stabilize before flying? How worn are your gimbals on your radio is it old? If all of that is good check and make sure the physical trims on your radio are centered before setting sub trims. Its very easy to unknowingly bump those while whipping the sticks around. NEVER touch those to trim the quad. Always set centers and endpoints in software.

Finally when you have to trim is it always in the same axis? If so then look for issues like bent shafts or binding on any motors that effect that axis. Then recheck how you mounted the KK2. Is it parallel with the frame and not leaning to one specific side? Is it loose and can move from vibration or tilting?
 
#8
I've had this issue since August so I don't think it's the weather. I had always assumed this was normal behavior but I finally get annoyed with it enough to ask. :(

Though you are right, it is quite cold here at he moment!

so . . . I'm wondering . . .

How's the weather been up in your part of Indiana?

Flying outside? Pretty cold this time of year? (listen to me talk -- it's a nippy 60°F outside my door :eek:)

Maybe dragging a warm copter and TX out into the harsher elements?

There's been quite a few reports of servos drifting in the cold (bring a warm tower-pro 9g servo outside and you can watch it "recenter" as it chills) I haven't seen an RX/TX do that before . . . but first time for everything . . .
 

cranialrectosis

Well-Known Member
Mentor
#9
Set the transmitter trims to dead center for all axis. Then using the KK2 receiver menu (I think), calibrate the subtrims on the transmitter until the KK2 is in synch with the transmitter. Leave the trims alone. The only time you should use the trims again for multirotors is to ensure that they are at center. :)
 
#10
I'll try to set the sub trim first and then re-calibrate.

It's GREAT to finally know that setting the sub-trims should be a one time deal. Both quads that I have use identical KK2 boards, and have the same issue with both (need to redo the sub-trims each time I decide to go out and fly).

So if I'm doing something wrong, I'm consistently doing it wrong. I'm just hoping there's nothing wonky with my transmitter.

Thanks for all of the responses!
 

PsyBorg

Wake up! Time to fly!
#11
True . . . but have you ever flown it with a KK2.1.5?

There actually was an electronics issue (not sure if it was fixed) in the TowerPro 9g servos drifting as the servo cold-soaked -- chill the chips, and the clock slowed down . . . and 1500ms to a sluggish freezing servo controller starts looking more like 1550 . . . or 1600 . . .or 1700 . . . someone here posted a freezer experiment they ran after isolating the issue a few years back.

I've never had a drift issue with any of the kk2.x boards I've flown but I don't get much cold soak in Middle Georgia (current late afternoon temp: 64°F -- it's getting chilly out there), so not seeing an obvious source of the headache, knowing the time of year, location and the potential for cheap electronics to have trouble keeping time as they chill . . . it's worth looking into.
Quite interesting and no I don't own a kk2 as I thought they were already outdated by the time I got into the hobby. Then I saw they were popular for tricopters after reading a lot of threads here in FT forums.

I was wonder Kilo Foxtrot as some pots wear and require a dead band be set for compensation. Now that you say you see the drift is there every time before you fly I believe CranialRectosis is correct that you may have calibrated the KK2 without the radio being set to neutral trims on all axis then matching the KK2 to the radio for centers.

By Chance have you watched any of David Windestals tricopter videos or KK2 board setup videos? he is the resident expert.

Other then that you could take a look with the quadcopter inside at room temperature to see if the same offsets are there to prove or disprove the temperature theory.
 

cranialrectosis

Well-Known Member
Mentor
#12
Check out step 6 Receiver test at about 2:10..

If you fly a KK2 in weather below 20* F, keep the lipos in your pocketses warm until you use them and let the KK2 cool off for 5 minutes before you fire it up.

Below 0 in Colorado I found the KK2 to be sketchy in autolevel but then again, being from California, I am pretty sketchy below 0 myself so YMMV. :)

Felt really good to see that video and hear that music again. It's been 2-3 years since I've had a KK2 in the air.
 
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#13
Check out step 6 Receiver test at about 2:10..

If you fly a KK2 in weather below 20* F, keep the lipos in your pocketses warm until you use them and let the KK2 cool off for 5 minutes before you fire it up.

Below 0 in Colorado I found the KK2 to be sketchy in autolevel but then again, being from California, I am pretty sketchy below 0 myself so YMMV. :)

Felt really good to see that video and hear that music again. It's been 2-3 years since I've had a KK2 in the air.
Thanks Guys. I have checked out David's vids and I had seen the one cranialrectosis posted before, but it does not hurt to have a refresher. This was probably a user error issue. But it's good to know that once the subtrims are set, these should be set for good.

Thanks again everyone.