Posted by Jordi Muñoz on December 30, 2009 at 1:30pm
I have dumb and obvious question (this is the cover my ass step) but i would like to hear the opinion of everybody. I really need it.This is the picture of new magnetometer for ArduIMU V1 and Flat version or any platform. It uses the HMC5843 and i2c translator that make it compatible with 3.3V and 5V uControllers (jumper selectable), that also works as a booster in case you are planing to mount it far, far away from the main board like the tip of your wing (for disturbing magnetic field reasons). It also has build in power regulator (only used in 5V applications) and my new invention: breakaway holes (yellow arrows). Can be also soldered directly to the ArduIMU Flat in case you want an small design. The next picture is an example of the breakaway holes:
The new ArduIMU flat batch will have this breakaway holes too!My PROBLEM is:If you look into the first picture you will see a huge 100uF capacitor (red arrow) next to the magnetometer (blue arrow). Do you think it will have a big impact on the magneto? I know that you have to calibrate the magneto to get it used to the ferro "i don't what" around it, that would be enough?Another angle:Luckily capacitors don't work like inductors LOL.Any help will be much appreciated (PLEASE!!). ;-)
Hi Jordi , I can't help you with choice of the capacitors problem :( but I see the DIYDRONEs symbol is in the break away portion , may be you want to put it some where in the main board :-) , may be you have done it already , just in case.
The capacitor will only contribute a "hard" error by virtue of the leads that may have some small ferrous component.
Otherwise, there will be much more pervasive errors from nearby components that are likely to acquire permanent magnetic fields, not to mention the induced magnetic fields from nearby cables carrying up to 2 amps of current. (as in Electronic control units for the motors)
However, the actual precision and accuracy of the HMC5843 isn't all that good anyway, so those field variations would probably get lost in the noise inherent in the system.
I have been testing it in my basement, surprisingly repeatable and works well. I have serial output of X,Y and Z sensor readings as well as the total magnitude mag=sqrt(sq(x)+sq(y)+sq(z)). I do see an elliptical nature to the magnitude as can be expected and can be corrected (scale factors and offsets). This is why I need my rf link working, to freely rotate sensor for data.
Yes i had the same problem, i just soldered a huge electrolytic one parallel to the original 10uF capacitor and the problem was gone. In this case i will use this 100uF ceramic capacitor (just in case).
Maybe your are right because mainly the capacitor is "ceramic" material, so it should not block/reflect magnetic fields.
Comments
Thanks for the info!
but the EasyStar cringed at the 1000grams, :)
G-822A CESIUM MAGNETOMETER
Otherwise, there will be much more pervasive errors from nearby components that are likely to acquire permanent magnetic fields, not to mention the induced magnetic fields from nearby cables carrying up to 2 amps of current. (as in Electronic control units for the motors)
However, the actual precision and accuracy of the HMC5843 isn't all that good anyway, so those field variations would probably get lost in the noise inherent in the system.
Hello Michael,
Yes i had the same problem, i just soldered a huge electrolytic one parallel to the original 10uF capacitor and the problem was gone. In this case i will use this 100uF ceramic capacitor (just in case).
Maybe your are right because mainly the capacitor is "ceramic" material, so it should not block/reflect magnetic fields.
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