View Single Post
  #18   Spotlight this post!  
Unread 07-01-2010, 22:15
Trevor_Decker's Avatar
Trevor_Decker Trevor_Decker is offline
Registered User
AKA: Trevor Decker
FRC #3504 (Girls of Steel)
Team Role: Mentor
 
Join Date: Apr 2009
Rookie Year: 2009
Location: Pittsburgh
Posts: 42
Trevor_Decker is an unknown quantity at this point
Re: Accelerometers & Gyros for N00bs

Quote:
Originally Posted by Chris Hibner View Post
It depends on the application (i.e. what are you using it for?).

If you're using the accelerometer for an anti-lock brake system, you would want to use a low-g range, like a 1.5g accelerometer, since the largest acceleration you should see under braking is about 1g, (the extra 0.5g is because you'll want a little room for vibrations and noise so you don't get distortion in your filters, but that's a more advanced topic).

If you're using the accelerometer for a side-impact airbag crash sensor, you'll want to use an accelerometer in the 250g range since you mount it right next to the impact and you can see accelerations well above 100 g's.

The idea is that you pick your sensor by determining (from physics or tests) what is the largest acceleration you will see. You should then select a sensor that can measure with just a little more range than this maximum.
So if I wanted to use an accelerometer to tell how fast a robot is moving (constantly adding/ subtracting the acceleration from the speed) , I would want a 2g accelerometer since the field is 54 feet in length, which divided by 32.174(earths gravity) = 1.678 which rounds up to 2.

would that be correct?
How accurate is a 2g accelerometer?

Thanks again for the help!
__________________
- Trevor

Team 3504 - The Girls of Steel 2011 - Present
2012 Pittsburgh Regional Engineering Inspiration, and website awards
Team 1743 - The Short Circuits 2009 - 2011
2009 Pittsburgh Regional Champions (thanks to 222 and 1218)
2010 Won Autodesk Animation Competition
2010,2011 Pittsburgh Team spirit award