Digital Compass affected by ground plane?

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I'm designing a circuit that involves a digital compass and I'm worried about effects from a ground plane directly under it.

The digital compass can pick up Earth's weak magnetic field . . . so can current going through the ground plane under the digital compass affect readings?

Average current is maximum 20mA at 3.3V, but with 1 amp current spikes for a few milliseconds about 20 times per second. Proper capacitors are placed between power and ground.

Should I keep the ground plane far away, or am I'm being over careful? If not for potential interference, there are specific benefits to the ground plane, so I don't want to 'just play it safe'.

I'd want to design around the problem *before* spending time/money prototyping, so experimentation is ruled out for now :?

edit: corrected spelling errors

How do YOU make a robot?
http://www.societyofrobots.com

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If you can perform your compass measurements between the current pulses you will almost cerainly be OK.

I am using a digital compass, ultrasonic range finder and multiple servos in a tracked-base robot setup wherein I perform a compass measurement just BEFORE
recalculation of servo desired servo positions.
I run my servo task every 500ms so the compass measurement occurs well after the servos have stabilized.

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That is a very good trick, wg0z. :D

However, you should try to route the high current carrying parts away from the compass.

I have found it useful to mount the drive transistors for the motors directly on the motor terminals on a small PCB. Then only a low-current switching signal goes from the controller to the motor assembly.

If you think education is expensive, try ignorance.

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Would anyone know if the ground plane could reduce Earths magnetic field around the sensor?

(and I like the software solution of taking measurements *before* sending new commands to the motors)

How do YOU make a robot?
http://www.societyofrobots.com

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yes the plane likely will reduce the effects of the already weak magnetic field of the earth. (effects will depend on orientation)

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Quote:

Would anyone know if the ground plane could reduce Earths magnetic field around the sensor?

On its own, no, it won't affect the Earth's magnetic field. However, current flowing through the ground plane will create an interfering magnetic field. Since the current can flow in a number of different paths across the ground plane the effects will be inconsistent. If you can force the current to stick to a known path things should be better.

Instead of dumping the current into the ground plane, why don't you make a special track for it? If you are concerned about the current carrying capacity of the track, do not solder mask that track and the soldering process will leave a layer of solder on the track increasing the effective thickness. (You can also do this by hand). :D

If you think education is expensive, try ignorance.