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Author Topic: Where to get 2-axis gyro?  (Read 5440 times)

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Offline Razor ConceptsTopic starter

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Where to get 2-axis gyro?
« on: October 12, 2008, 05:27:49 PM »
I'm in need of a 2-axis gyro for a helicopter UAV. I've seen a lot out there, but not sure what is the best. Any ideas?

I'm planning on using a 3-axis accelerometer (3d one from dimension engineering) to keep the UAV in a moderately level state, and the gyro will fine tune it to be exactly level, as I think the vibration from the UAV will make the accelerometer unaccurate in fine readings.

Offline dunk

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Re: Where to get 2-axis gyro?
« Reply #1 on: October 12, 2008, 07:18:09 PM »
i've no idea if they are any good but i just ordered a pair of these for my aerial platform:
http://shop.ebay.ie/?_from=R40&_trksid=m38.l1313&_nkw=angular+rate

can't go wrong at that price...


dunk.

Offline Razor ConceptsTopic starter

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Re: Where to get 2-axis gyro?
« Reply #2 on: October 13, 2008, 01:42:06 PM »
Hmm I think I'll just buy two gyros for radio controlled helis, I need the high accuracy they provide.

Also, best compass sensor? I've been looking at this one:  (360 divided by 64 bit = 5.625 degree resolution?)
http://www.trossenrobotics.com/hitachi-hm55b-compass-module.aspx

Or would spending $60 for a 0.5 degree resolution be worth it?
http://www.sparkfun.com/commerce/product_info.php?products_id=7915
« Last Edit: October 13, 2008, 01:48:00 PM by Razor Concepts »

Offline Admin

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Re: Where to get 2-axis gyro?
« Reply #3 on: October 15, 2008, 05:31:21 AM »
Dunk . . . it says 'Prototype PCB', so brave of you :P

Razor, I got the 5-axis gyro from sparkfun . . . the output resolution is poor though, you'd have to amplify it if you want to do something higher precision.

Quote
5.625 degree resolution? . . . Or would spending $60 for a 0.5 degree resolution be worth it?
5.6 deg res is poor in my opinion. For $60, get the better res. But it also depends on the operating environment, like if you expect high interference, you aren't going to get good accuracy no matter what . . .

Offline Razor ConceptsTopic starter

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Re: Where to get 2-axis gyro?
« Reply #4 on: October 20, 2008, 10:55:29 PM »
5.6 deg res is poor in my opinion. For $60, get the better res. But it also depends on the operating environment, like if you expect high interference, you aren't going to get good accuracy no matter what . . .

What would you consider high interference? I noticed that you have a Blade CX helicopter, I'm trying to use these in a Blade CX2. The gyro for yaw is right up near the motors, so is that safe to assume theres little noise coming from the motors?

Also, is there a gyro board that is accurate enough without amplification? The datasheet says the IDG300 (gyro on the 5dof imu) says it is rated for 500 degrees a second. Would switching to a lower degrees/sec (sparkfun sells 75 degrees/sec gyros) improve accuracy?

And going off on a tangent.. the 75 degrees/sec uses a ADXRS401 gyroscope. In RC helis the Futaba GY401 is one of the most popular gyroscopes out there, wonder if the GY401 uses the ADXRS401.
« Last Edit: October 20, 2008, 11:15:12 PM by Razor Concepts »

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Re: Where to get 2-axis gyro?
« Reply #5 on: October 24, 2008, 03:36:17 AM »
Quote
What would you consider high interference?

When the interference is greater than the platforms ability to stabilize - subjective question gets subjective answer :P

Quote
I noticed that you have a Blade CX helicopter, I'm trying to use these in a Blade CX2. The gyro for yaw is right up near the motors, so is that safe to assume theres little noise coming from the motors?

Nope, doesn't mean anything at all. That just means the people who put it there decided interference was acceptable given their design requirements and specific circuitry . . .


Anyway, you need to tell me what you consider accurate enough for your application . . . Have a look at this when it comes to accuracy:
http://www.societyofrobots.com/robot_faq.shtml#robot_accuracy_tradeoff

 


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