Comments on: Accelerometer on Robot Finger

By: Don Anderson

Don Anderson — Fri, 16 Apr 2010 01:31:38 +0000

Hi Nate,
I’m trying to compile your code above for the adxl accelerometer using a Arduino Duemilanove. It stops at the following line of code:
rv.data[i] = (((int16_t)msb) < < 8) | lsb;
Would it be possible for you to send me a .pde sketch file I could work off of? I'm a new to electronics and any help you could provide would be appreciated. I'm trying to put the the accelerometers on a kayak paddle and life vest. Have you had any luck running 3 or more adxl345's on the same Arduino analog input pins 4 &5?

Thanks for any help you can provide,
Don Anderson

By: EyeTic

EyeTic — Thu, 03 Dec 2009 21:11:53 +0000

Nate thanx! I’ve managed to translate it well enough for my app! The problem was mixed types, I used chars instead of bytes, and it pretty much messed up the readings…

You can see the final thingie here: http://www.youtube.com/watch?v=BJeohcZssBU

By: Nate

Nate — Thu, 26 Nov 2009 19:20:41 +0000

@guest2-
We actually didn’t use resistors, and connected it straight to the arduino pins specified for those. We were a little confused about the pull up resistors, but it seemed to work without them. We were thinking it might effect the bandwidth of the measurements, but not really sure. You should reply if you investigate more into this topic.
Thanks

By: Nate

Nate — Thu, 26 Nov 2009 19:14:07 +0000

@EyeTic-
Well, for our application, we didn’t need to do this, but I may be able to tell you which direction to go.
Each individual axis has three positions that can allow you to translate output from accelerometers into g’s.
Pointing an axis down should be the value corresponding to 1g, pointing it up should be -1g, and having it horizontal should be the zero value. Using these three points for each axis you should be able to do a linear regression and get a transform function for each axis.

By: EyeTic

EyeTic — Wed, 25 Nov 2009 11:18:07 +0000

Hi!
I’ve managed to work out the data reading from the adxl345, how do I translate the values to g’s though? The pos/neg doesn’t seem to be consistent, and I can’t figure out how to arrange the bits so that I get it in the right format

Thanx!

By: guest2

guest2 — Sat, 21 Nov 2009 17:20:24 +0000

May I ask what pull-up resistor values you used for the SDA and SCL lines? Thank you.

By: Nate

Nate — Fri, 06 Nov 2009 16:22:50 +0000

Ah, yes there was a problem with the html escaping. It’s fixed now.

By: guest

guest — Fri, 06 Nov 2009 06:02:54 +0000

byte lsb, msb;
for (i=0; i<< 8) | lsb;
}

in the read routine. Is there something missing here? I presume you are creating and int out of the lsb and msb for the x value…but the syntax/construct looks strange