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[DPRG] voltage problem in IMU

Subject: [DPRG] voltage problem in IMU
From: Jon Hylands jon at huv.com
Date: Wed Jul 5 09:24:42 CDT 2006

Hi everyone,

I'm making a serious run at building my tiny AUV, NanoSeeker. You can see
pictures and info at http://www.huv.com/nanoSeeker

In the nosecone, I'm planning on putting a 6-axis IMU together with a
2-axis digital compass. The IMU will be (assuming I can figure this out) a
5-axis breakout board from Sparkfun (3-axis accel + 2-axis gyro) plus an
ADXRS breakout board, mounted upside down on the bottom of the 5-axis

On a 3rd board on top of both of these, I'm going to have an 8 or so
channel A/D converter with an I2C interface, and the Honeywell HMC6352
2-axis digital compass, which is also I2C. Interfacing this whole thing
will be a Tiny2138 board from NewMicros.

The compass, the 5-axis IMU board, and the Tiny2138 are all 3.3 volt parts.
The 5-axis IMU has 5 analog outputs, which are all 0 - 3.3 volts. The I2C
bus will be run at 3.3 volts. The problem I have is the ADXRS board is a 5
volt part.

Reading the data sheet, the ADXRS seems to put out 0.5 to 4.5 volts. Is
there any simple (read, really small components) way to maybe cut that
voltage in half, so the full scale output becomes 0.25 - 2.25 volts? I'm
reading it with a 12 bit A/D, so I have a fair amount of resolution.


   Jon Hylands      Jon at huv.com      http://www.huv.com/jon

  Project: Micro Seeker (Micro Autonomous Underwater Vehicle)

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