Arduino IMU

Forum 2005-2010 (read only) Hardware Interfacing
#1

Hello all,

I recently purchased a 5DOF IMU from sparkfun to interface with my Arduino. I have since found that an ADC is required to interface the gyro outputs the the Arduino.

Could anyone recommend an ADC for me? To my understanding I need a 2-channel 12-bit ADC.

Thank you for your responses,
Calaway21

#2

Just wondering, any reason you can't use the A/D converters built-in to your Arduino?

#3

That's a good question. On the diydrones website a user posted that the 5DOF IMU from sparkfun cannot interface directly with the arduino. I am currently unable to find the article but it indicated that the arduino can only detect 2.44 mV changes whereas the gyro on the IMU has an output differential of 2mV/degree. This seems to cause a necessity for an external ADC to cope with the output differential. Does this seem correct? Or can anyone challenge this concept with the built-in Arduino ADC?

Your posts are much appreciated, Calaway21

#4

Ah, I see. It's not quite that simple. The IDG300 has a sensitivity of 2mV/deg/s which means that WHEN you are rotating a 1 degree per second, the signal will be 2mV. If you are rotating faster, well, you'll get a higher signal.

So the question is, do you NEED to sense 1 degree per second rotation?

With a 5V analog reference, there are 1024 steps (10 bits) so each step is 4.88mV, which corresponds to 2.44 degrees per second of rotation. So you'll either sense 2.44 degrees/second, 4.88 degrees/second, etc. Is that good enough?

This is all pretty theoretical anyways:

  • Down in the mV range, just using plug-in modules is not going to be electrically "quiet" enough to shield from outside noise sources. A few mV is really "down in the muck" without proper ground planes, shielding, etc.

  • The IDG300 has specs like +/-10% initial accuracy, +/-2% cross-axis sensitivity (i.e., you rotate in Y, you see 2% of it in X), +/-0.3V initial error from nominal 1.5V....this thing is just not a PRECISION instrument so having 2mV resolution is not buying you much I don't think.

#5

Thank you RuggedCircuits. That really clears things up for me. For now, high precision is not necessary so long as it can function properly.

#6

any one have a code for IMU 5 dof with arduino using kalman filtering?

#7