Relocate the magnetometer?

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Taipan
Posts: 6
Joined: Fri Jan 08, 2016 11:40 am

Relocate the magnetometer?

Post by Taipan »

Hi,

I understand that the magnetometer's accuracy can be compromised by circulating currents to the motors. Has anyone successfully disabled the magnetometer on the flight controller PCB and installed a remote magnetometer up with the GPS module?

I was thinking of using something like the SparkFun Triple Axis Magnetometer Breakout - HMC5883L (https://www.sparkfun.com/products/10530) - mounted up in the GPS housing. But, I would first have to disable the HMC5883 that is already on the flight controller PCB (a Hobby King MultiWii Pro board - the red one).

Regards,

Taipan

Kbev5709
Posts: 451
Joined: Mon Aug 17, 2015 5:56 pm

Re: Relocate the magnetometer?

Post by Kbev5709 »

Taipan wrote:Hi,

I understand that the magnetometer's accuracy can be compromised by circulating currents to the motors. Has anyone successfully disabled the magnetometer on the flight controller PCB and installed a remote magnetometer up with the GPS module?

I was thinking of using something like the SparkFun Triple Axis Magnetometer Breakout - HMC5883L (https://www.sparkfun.com/products/10530) - mounted up in the GPS housing. But, I would first have to disable the HMC5883 that is already on the flight controller PCB (a Hobby King MultiWii Pro board - the red one).

Regards,

Taipan

You can't do a remote mag with that FC. I have one too. There are some boards where you can just cut the inputs to the mag but not on that board. With that FC you need at least 20 mm standoffs spacing the FC from stray currents below. I have no problems at all with mine which is installed on said standoffs, and I have a 25 amp Q brain 4 in one ESC unit 21 mm directly below it.

This board is $35.00 and comes ready for a remote mag: http://www.readytoflyquads.com/multiwii ... gps-option
I have one of those as well as this GPS (with mag on the backplane) http://www.readytoflyquads.com/ublox-6h ... nd-compass
with this ground plane extender http://www.readytoflyquads.com/ublox-6m-gps-shield-hood
which also acts as an RF shield separating the unit even more from stray currents below.
This setup is awesome and works beyond all expectations.

handsomejackuk
Posts: 97
Joined: Mon Sep 08, 2014 12:25 am

Re: Relocate the magnetometer?

Post by handsomejackuk »

some of the gps modules have a mag already in them i have a neo 6m i think it is, but this is on the i2c bus arduino pin a4 a5.. if thats any help, also you can disable the onbaord mag by using an alternative i2c address...


Taipan
Posts: 6
Joined: Fri Jan 08, 2016 11:40 am

Re: Relocate the magnetometer?

Post by Taipan »

Kbev5709 wrote:I have no problems at all with mine which is installed on said standoffs, and I have a 25 amp Q brain 4 in one ESC unit 21 mm directly below it.

My magnetometer is about 40 mm above a Q-Brain 4 in 1 ESC, so it sounds like it should be fine. I haven't done any test flights yet to know for sure ... :D

If I do have issues, you have both given me some ideas to consider, thanks.

Kbev5709
Posts: 451
Joined: Mon Aug 17, 2015 5:56 pm

Re: Relocate the magnetometer?

Post by Kbev5709 »

handsomejackuk wrote:some of the gps modules have a mag already in them i have a neo 6m i think it is, but this is on the i2c bus arduino pin a4 a5..
The pins on his board are different.
handsomejackuk wrote:if thats any help, also you can disable the onbaord mag by using an alternative i2c address...
I, not being a great programmer, would like to know how to give my onboard mag on my Pro board from HK, an alternative i2c address. Can you explain how it's done? Do I need to change the address in the sensors.cpp section? Lets say I change that address. How is the new outboard mag recognized. What if it is the same make of mag? The new mag, hooked up to the i2c to replace the one with the changed address, is given a new i2c address? How does the rest of the code know that the new mag with a new address is there? Do you give it the address of the one you changed? Since the mag whose address you changed is still physically wired in to the i2c circuit, wouldn't the FC recognize the old mag instead of the new one again with the old address entered again?

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