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Converting accelerometer adc values to Gs
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kein



Joined: 23 Jul 2007
Posts: 103

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Thanks
PostPosted: Wed Sep 05, 2007 4:15 pm     Reply with quote
Quote:
If( VinX > 1.63 )
{
Calibrate_Output = (( VinY - 1.63 ) * MA_x ) + 1.65

}else if( VinX == 1.63 )
{
Calibrated_Output = 1.63

}else if( VinX < 1.63 )
{
Calibrated_Output = 1.63 - ((VinX - 1.63 ) * MB_x )
}
*buf_xptr++ = Calibrated_Output;

Calibrated_Output = 0;

/* for the case of "Y" */

VinY = READ ADC Value for Y_Axis

If( VinY > 1.64 )
{
Calibrated_Output = (( VinY - 1.64 ) * MA_y ) + 1.65

}else if( VinY == 1.64)
{
Calibrated_Output = 1.64

}else if( VinY < 1.63 )
{
Calibrated_Output = 1.64 - ((Vin - 1.64 ) * MB_y )
}

*buf_yptr++ = Calibrated_Output;

Calibrated_Output = 0;
}

Thanks alot. I think the input voltage in the following line should be VinX instead of VinY
Code:
If( VinX > 1.63 )
   {
          Calibrate_Output = (( VinY) - 1.63 ) * MA_x ) + 1.65
   
   }

and there should be VinY in the following line(typo error)
Code:
else if( VinY < 1.63 )
   {
          Calibrated_Output = 1.64 - ((Vin - 1.64 ) * MB_y )
   }

thanks
collegeman
Guest
pulling up accelerometer using pic16f877a
PostPosted: Fri May 01, 2009 5:38 pm     Reply with quote
My fellow students and I are trying to program a pic16f877a controller to control a rc car. We are using an accelerometer and want to integrate the signal to get the distance traveled. We are having a hard time trying to figure out how to get the information from my accelerometer to be able to integrate it. can any one help us with this.
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Sun May 03, 2009 10:52 am     Reply with quote
To understand, if you can get a meaningful distance measurement, I suggest to to determine the expectable error of your acceleration value, put in the intended duration of measurement after zeroing the position and calculate the position offset.
Code:
s = 0.5 a * t**2

I fear, you won't go far with it.
nachum



Joined: 23 Aug 2009
Posts: 3

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Re: Converting accelerometer adc values to Gs
PostPosted: Sun Aug 23, 2009 9:41 am     Reply with quote
hi
You have the code to reading from ADXL330 ?
vinniewryan



Joined: 29 Jul 2009
Posts: 154
Location: at work

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PostPosted: Sun Aug 23, 2009 1:22 pm     Reply with quote
Wow this is all great help to me as well! I'm working with an accelerometer right now as well, though I do have one question in regard to wiring it to the PIC: will I need any extra components in order to get the accelerometer to send signal to the PIC? All I want to do is have the pic read the x, y, and z inputs as decimal values. I've looked it up but everything I've found is specific to some other circuit and I don't need anything else. Accelerometer, PIC, battery.

Thanks!
nachum



Joined: 23 Aug 2009
Posts: 3

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adxl330
PostPosted: Sun Aug 23, 2009 2:04 pm     Reply with quote
hi
You read the data from the pic...to computer

You have electric diagram of the circuit ?
u can send me the code that wrote or what you have ?
nachum.adi@gmail.com
nachum



Joined: 23 Aug 2009
Posts: 3

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Re: pulling up accelerometer using pic16f877a
PostPosted: Sun Sep 13, 2009 12:01 pm     Reply with quote
hi
You read the data from the pic...to computer

You have electric diagram of the circuit ?
u can send me the code that wrote or what you have ?
nachum.adi@gmail.com
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sun Sep 13, 2009 2:36 pm     Reply with quote
Nachum,
He is buffering the output of the ADXL330 with 3 opamps which are
configured as Voltage Followers. It's similar to this circuit:
http://www.mikroe.com/pdf/accelboard_schematic_v202.pdf

Read this thread for more discussion on the best OpAmp to use:
http://www.ccsinfo.com/forum/viewtopic.php?t=31907

In the same link, you can see that he's using ADC channels 0, 1, and 4
for the ADXL outputs X, Y, and Z. The output of the opamps goes to
pins AN0, AN1, and AN4 on the 16F877.
avneesh



Joined: 27 May 2010
Posts: 1

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Adxl335
PostPosted: Thu May 27, 2010 5:33 pm     Reply with quote
Hi
I have a similar problem with using the adxl335. I read the values using my 12 bit ADC in the aduc7020. The result is a 12bit binary, which I can convert to decimal, but I want to know how to get the values to voltage.

when the adx335 is flat on the table the values of x=2773 y=2857 z=1192
note: these value are decimal

How do I convert these values to voltage... the math to do this what I need.

Thanks.

I'm new to this so any help will be appreciated.
Also I would really appreciate a quick back, I need to complete this work very soon.

+++++++++++++++++++++++++
The ADuC7020 micro is off topic.
Please ask on a ADuC7020 forum.

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