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Author Topic: Compass or Gyro  (Read 2612 times)

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Offline DarkbluestarTopic starter

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Compass or Gyro
« on: December 30, 2007, 07:13:08 PM »
I am working on an omni directional robot and I am going to be using a single laser mouse placed in the exact center of the robot in order to find out the robot's x,y location. I figured that I need to know what direction I am facing and that I would need either a compass or a gyro. However, I am not exactly sure which one would be best for my application. I only need to run the robot for about 3 minutes at a time and it will hopefully be moving pretty fast.

Offline sdk32285

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Re: Compass or Gyro
« Reply #1 on: December 30, 2007, 07:48:04 PM »
Hi
I would recommend the compass as they are usually easier to use, and you don't need to deal with the gyros drift (a cheap gyro can drift degrees per second).
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Offline DarkbluestarTopic starter

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Re: Compass or Gyro
« Reply #2 on: December 30, 2007, 08:01:02 PM »

Offline mpuvdd

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Any man who reads too much and uses his own brain too little falls into lazy habits of thinking-Einstein

Offline sdk32285

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Re: Compass or Gyro
« Reply #4 on: December 30, 2007, 11:21:17 PM »
The parallax one looks nice even thou I don't see the resolution anywhere...
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Offline DarkbluestarTopic starter

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Re: Compass or Gyro
« Reply #5 on: December 31, 2007, 12:47:15 AM »
The parallax chip looks nice but I am already using the only serial interface on my mcu. I am using the ATMEGA644. I was thinking about the acroname one because it has an I2C interface which I have room for.

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Re: Compass or Gyro
« Reply #6 on: December 31, 2007, 08:23:16 AM »
If you are only running it for 3 minutes than a gyro would be infinitely better (drift will be insignificant in short time spans). The problem with a compass is that motors and nearby objects affect the reading.

Are you doing a three wheel or four wheel omni robot?

Make sure your laser mouse is always perfectly flush with the ground, or it won't work.

Offline DarkbluestarTopic starter

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Re: Compass or Gyro
« Reply #7 on: December 31, 2007, 01:00:43 PM »
Thanks for the info. This is for a competition and other robots will be around so that might influence the compass. I am going to be using a four wheel, pretty much like your omni Admin, and I am going to try and put some sort of suspension on it(ME member on my team is working on it). I am planning on putting the mouse on a suspension system as well so it will always contact the ground(I'm working on that). What would be a good choice for a gyro? I am not really familiar with them and I don't really understand which one I should use. I am mostly going to use the gyro to keep the robot from rotating. I do not want the robot to rotate at all, that's why I am going to use omni wheels.

Offline DarkbluestarTopic starter

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Re: Compass or Gyro
« Reply #8 on: December 31, 2007, 01:31:05 PM »
I found a compass with SPI and analog interface, how does it look? http://www.sparkfun.com/commerce/product_info.php?products_id=8372

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Re: Compass or Gyro
« Reply #9 on: December 31, 2007, 02:12:35 PM »
Quote
I found a compass with SPI and analog interface
you mean gyro? :P

do you need SPI?

what would you consider acceptable error in degrees? (you will always have error)

Offline DarkbluestarTopic starter

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Re: Compass or Gyro
« Reply #10 on: December 31, 2007, 02:32:22 PM »
Yes gyro sorry :D I don't need SPI, but my mcu has an SPI interface so I was just noting that. I am trying to look for as small an error as possible. I am not really sure what would be acceptable. I just need it to be accurate enough so that if my robot accidentally rotates I can compensate for that change. I need my robot to always face the same direction.

 


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