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Feb 17, 2009, 01:55 PM
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How to read gyro datasheets


You can get the worst case drift from the datasheet. They all have a null drift over temperature or zero rate vs temperature parameter. If it's in volts, you divide the volts by the volts per deg/sec parameter. This is the key parameter 4 U.

IDG300: 150 deg/sec
IDG500: 25 deg/sec
ADXRS150: 26 deg/sec
MLX90609 - 150: 7.5 deg/sec
LISY300AL: 5 deg/sec

So we got the 2 worst gyros in the world. 2007 was the dividing line where they got a lot more accurate, except for the Silicon Valley ones. No-one is anxious to spend $100 on LISY300AL prototyping boards, so the idea of accurately predicting the outcome of cheap gyros without buying a PC board is dead.

The days of magnetometers & accelerometers are over. If they're really down to 5 deg/sec, modern IMU's can go for over 20 minutes without any corrections.

FYI, polulu.com has the same breakout boards as $parkfun for slightly less money. The polulu LISY300AL can take 5V & lowpass filters the output. You need a 3.3V reference either way because A/D converters are nonlinear.
Last edited by Jack Crossfire; Feb 17, 2009 at 02:02 PM.
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Feb 22, 2009, 01:09 PM
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kbosak's Avatar
I believe your drift for IDG300 is datasheetingly-pessimistic because it has simply narrower temperature range, within reasonnable outdoor conditions or even in mid winter it behaves very well provided you dont change more than 20degC or so.
95% agree on general conclusion, however I believe because of initial tolerances, Kalman or similar is still required.

I wouldn't believe in LISY300AL. It is too cheap. I would believe in MLX, it has internal temp compensation.

ADXRS150 is BGA, so forget it.

IDG500 is a nice find, how did I missed this one?

The problem with LISY300AL is lower resonant frequency, cheap acceleros with that resonant freq caused problems on some of my planes. I will evaluate it one day.

There is one good reson to stay with IDG: fits on a single PCB. Ihis means reliability, low cross section, and cheaper prototyping.


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