MultiWii

I noticed when ascending or descending.. the quad tends to yaw to a certain deg.. and backward when descending.. so i did a small bench test...

video shows that the mag is affected by motors

http://www.youtube.com/watch?v=Hdld9I15ylk

mag is connected but not turned on..

board. AIOP1.1
motor Turnigy park 300 1080kv
bs12A simonk fw
3s battery
m2m 50cm


anyone has idea how to solve it?...

thanks

jy0933 wrote:I noticed when ascending or descending.. the quad tends to yaw to a certain deg.. and backward when descending.. so i did a small bench test...

video shows that the mag is affected by motors

http://www.youtube.com/watch?v=Hdld9I15ylk

mag is connected but not turned on..

board. AIOP1.1
motor Turnigy park 300 1080kv
bs12A simonk fw
3s battery
m2m 50cm


anyone has idea how to solve it?...

thanks

I have the same MAG problem - mag turns left buy around 20 degrees max at full throttle. It is coming from power wires, close to magnetometer.

The solution is to relocate the MAG further away from all power wires, like is done, for example, by DJI - MAG is in the GPS module, witch is 10cm or more away from all electronics.

Other solution is to use higher voltage batteries (4S-6S or more) with suitable motors, plus thicker and shorter power wires, then the current in wires will be less and the magnetic field generated also.

I have ordered and am waiting for HMC5883 breakout boards to arrive soon, and will take off the MAG from my CIUS AIO Pro board and connect the external one.

I don't believe that the compass is impacted by the motors, but by the power pack cables.

Rationale: electrically commutated motors like brushless motors provide a magnetic field rotating of roughly 1000 Hz.
The iron motor housing shields this field. The distance between motors and compass is quite large.

But, the cable of the accu pack leads a high current at high throttle. This high current result in a high static magnetic distortion of the earth magnetic field.
There is hardly a way to shield this distortion without influencing the earth magnitic field.

As a fast solution I propose
- not to split the plus cable and minus cable of the akku pack. Both should be as close together as possible.
- a high distance between this cables and the compass. Try to set the compass as high as possible and the power distribution plate (if there is any) as low as possible, close to the accu pack.

I hope that will help a bit.

it makes sense that the compass is affected.. but since mag is not turned on... how would the turning happen

Your video shows that the mag is affected. What happens if you fly with mag turned on?

What is wrong with your Cycle time: 4000 to 5000?

I have AIOP v1.1 and I have cycle times around 3000.

i fixed the cycle time to 5000 in code..

jy0933 wrote:i fixed the cycle time to 5000 in code..

And what is benefit for fixed cycle time?

What I made:

My set up is (from bottom to top) battery, power distributor (cables), CD´s box, MWC Pro, GPS antenna, and CD´s cover.

As I had that problem, about 12 degree when full throtle, with 20 amps each motor, I covered the CD´s box (it sould be almost flat) with an adhesive aluminium foil with ground derivation to one - pin (minus).

Now is only 1 degree.

Mmmm? seems too easy :-/, could you explain the reason of this? Does this rout the wire inducted magnetic fields away from the mag sensor?
manu

Yes, it is as simple as it looks.

The idea is to set a metal shield between the wires and the electronics, and connnected to - minus. The same as others do under the GPS antenna.

My first atempt was with food aluminium film, but it moves too much. So I tried with adhesive aluminium 5 cm roll, and it works.

You can´t loose anyting trying.

hi sounds interesting
can you show my the picture. What do you mean with "and connnected to - minus"
It is always nice to see a actual picture.

many thanks in advance

Hey,
intresting, i had the same idea without reading javiers post. It happened to me as i opened up my laptop for cleaning. There is also a alu foil on the case with connection to gnd. With my basic understanding of shielding it made perfect sense. I know shielding is very important for nice data transfers.
As my FC is boxed in a "Tupperware-casing" , i decided to add 2 layers self-adhensive alu-foil to the bottom of it. I did connect this foil direct to the gnd of my lipo. (to avoid gnd-looping)
Know what? I am quite impressed.
As i started to use the Multiwii Pro (FFIMU v2) without external mag, i ran into big problems....
Around 30° mismatch at full throttle.
Now with the case-gnd-mod, i got only 10° mismatch at full throttle. Will keep experimenting, if it helps to add another alu-foil layer, to eliminate the last 10°motorpower induced error.
Beside, what i did not expect, my GPS module (MTK) works much much much better. At same location and weather situation ,Instead of 6 sats i got a solid 9-10 sat lock.
So this seems to be a real good option to shield your components.
Btw. i had to recalibrate the mag after this mod, as it has gone wild with the old calibration data.

Maybe we are on a easy way to get rigid mag readings, even if they are soldered directly onto fcboard.

Hope it helps others also to get rid of that problem. I will do some more GPS testing next few days.


Wohooo i like such improvements!

offtopic:
(btw. im on lastest dev now, seems to work quite nice.) But anyhow GUI is troubeling more and more on Win7 (64-bit). I use the 32-bit version of GUI, as 64-bit does not start. (Even if selfcompiled.) I get grey box "of death?" after some secound or minutes of fc connection. I had sometimes the feeling it would depend to copter movements, especial if i yaw my copter. I was not able to do a mag calibration on GUI. I had to use KV-OSD to see north, while calibration. Thx KV
Did all the Java update stuff, chose compatibility mode etc.
Its same behaviour on my laptop. Am i missing something?

Greetz Noc

edit: will try gui on linux these days

Hi.

You should be able to lower the magnetic field by twisting the plus and minus cable together.
If the both cables are flows through by same current, the magnetic field will disturb...

But with some very fat cables it will be hard...

Noctaro: I used also only 32bit version of GUI, otherwise that I have x64 system...

Hi,

I have a MW SE 2.5 on Tarot TL250 frame. Mag was having serious interference problems creating yaw instability (about 20+ degrees shift). I cut up a tin can (for a shield), placed it directly under FC (about 3 mm froom PCB) and connected it directly to battery minus. This eliminated my mag problems - I can not detect any yaw shifting! The can must be ferrous. The shield size is about 25 x 25 mm.

Thanks for the shielding idea, it definitely works!

Dennis

hahaha, great idea! i will definately give this tin can mod a try. It sounds to me like styleneed