Headfree mode problem

[fly4fun6719]

Being new to quads I was wondering if somebody could give me some advice on a problem.I have just installed and programmed a Multiwii se 2.5 with CN06 GPS and IC2 Nav board.Modes activated are Horizon,headfree,GPS hold and return to home through aux 1&2.When I activate headfree the quad doesn't act correctly.From my understanding headfree uses heading information to know the orientation of the quad.Headfree acts as though the heading information has a large error and thought maybe it was caused by electromagnetic interference.
If that is the case could somebody advise me what I could use underneath the board to shield it?

[Cereal_Killer]

Interference is a MAJOR issue with headfree mode however there are several other things it can be too so you've got some testing / changing to do before writing it off.

First off what MAG is on your GPS module and how do you have it mounted?
Do you have your magnetic declination properly converted to tenths of a whole (from degrees & minutes) and have it correct polarity (- for W & S, + for E and N)?
Third have you twisted / braided the wires)?

Are you engaging MAG mode at the same time as headfree (in my experience you should be)?

[Cereal_Killer]

Also, the basics; have you calibrated the mag and does it point to the correct directions? North MUST be the front of the quad, if orientation is off it'll never work.

[fly4fun6719]

Thanks everyone for the advice.The board type is a Crius Multiwii SE version 2.5 using a ATmega 328P micro controller,MPU6050C 6 axis gyro/accelerate,HMC5883L 3 axis digital magnetometer and a BMP085 digital air pressure sensor.The magnetic declination for the area I fly has been added to the code.I don't know whether it was done correctly as it was found by a search on the web.The accelerater and magnetometer were calibrated using the graphical GUI.
As yet I haven't twisted the wires to the ESC's so that will be my first job.I was thinking of putting a thin copper plate under the flight controller and connecting it to the negative side of the battery to try and cancel any interference.

[Cereal_Killer]

A copper plate is unlikely to work,I tried copper, steel and aluminum, what it's always ended up taking for me is distance, I now mount the GPS / MAG up on a 5" mast (3" or more should be good enough on a mini quad). I've also got good enough results for MAG mode (but NOT headfree mode) by placing the sensor out on one arm OUT PAST the motor so it only had the interferance from the one motor to contend with. It wasnt accurate enough for full heading hold function but again it did work well enough for MAG mode to work (if you're not sure MAG mode alone prevents drift on the yaw axis (from things like wind and the drift over time in the gyro but you still control it normally)

Post your location and we can tell you the proper conversion. For example, 6*45'W (6 degrees 45 minutes West) would convert to -6.75 because 45 minutes is 3/4 of an hour and W is negative.

[fly4fun6719]

Thanks for all the help and information Cereal Killer.My position is Latitude -33.944873 Longitude 151.007525.I have gone ahead and twisted the power cables to the ESC's.Initial checks in the backyard after doing the mod have been encouraging.Headfree and GPS hold appear to be working but will do more extensive checks when I have more space.Still haven't checked the "return to home".I believe this be a bit exciting when you first try it.