Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

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brink.daniel
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Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby brink.daniel » Thu Mar 17, 2011 1:15 am

Hi guys, I'm busy building myself a 6wd all terrain explorer robot, but I'm having trouble with the spatial sensor's compass. It works perfectly when away from my robot, but is completely wrong when attached to it (anywhere within 60 cm). I tried running the calibration app while the sensor is attached to the robot, but its not correcting the problem. Am I forgetting something simple here? Any ideas on how to correct the problem?

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Re: Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby erik » Fri Mar 18, 2011 11:43 am

Is there any really strong ( > 3Gauss ) and/or changing magnetic fields nearby? Such as high current motors, solenoids, etc.?

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Patrick
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Re: Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby Patrick » Fri Mar 18, 2011 11:44 am

You'll definitely need to calibrate it after it's mounted. What type of trouble are you having with the calibration program? Are you running the 2-axis or 3-axis calibration? Does it behave ok when your robot isn't moving? I imagine your motors could interfere fairly heavily with the compass.

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Re: Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby brink.daniel » Sun Mar 20, 2011 2:22 am

Hi guys, thank you for your replies. I'm using a dagu wild thumper 6wd chassis, so there are 6 motors and a 1064 - PhidgetMotorControl HC causing magnetic interference.

I've been running the .net calibration program (source code), which came with the sample code, in 3-axis mode while the robot is power on and the spacial sensor mounted to it. I have not tried the 2-axis mode yet as I need 3-axis data. Is there anything specific I should do with the output after running the calibration program? Or is the calibration program suppose to automatically correct my sensor readings/settings after running it?

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Re: Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby Patrick » Mon Mar 21, 2011 9:09 am

The calibration program will give you 9 numbers. You then need to plug these numbers into the CPhidgetSpatial_setCompassCalibrationParameters function after opening the PhidgetSpatial in your program - these values are stored/used in the library and don't stick around on the PhidgetSpatial itself.

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Re: Magnetic Interference (1056 - PhidgetSpatial 3/3/3)

Postby brink.daniel » Tue Mar 22, 2011 12:09 am

Thats what I was doing wrong! Thank you. Will try it out later in the week when I get a chance.


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