Re: [PICLIST] [EE]: "Tilt-o-meter" for RC plane ADXL202 Results!

Since reading a post earlier negating the use of an accelerometer as an
absolute position sensor in a powered rc model airplane I set out to see if
it was true.

Test results on Sunday are promising. The test included mounting an ADXL202
into an RC airplane to measure pitch and roll. One senser was mouted with
the X and Y axis parallel to the earth. On the bench steady readings of down
to 2 tenths of a degree were acheived. A Pak-IX was used for calculations.

RC Airplane readings during "somewhat" straight level non accelerating
flight swayed between -4 and +4 degrees of pitch and roll during snapshots,
Peaks up to about +/-8. Snapshots were taken at 100ms intervals and
controlled by a separate rc channel from the transmitter. During the 100ms
interval 8 samples were read and averaged per axis.

Next test was to turn OFF "differential ailerons" and "aileron to rudder
coupling" and bank the airplane and take further readings. The same degree
of error occured more or less.

For those that are familiar with the ADXL202, I used 249k for Rset and 0.1uf
for Xfilt and Yfilt. 0.1uf gives a bandwidth of 50hz. I am guessing that a
higher value of X/Yfilt and better padding of the sensor should bring the
readings down a degree or so.

But all in all the ADXL202 seems to do what it was partly advertised for. I
have yet to put the Precision Navigation "Tilt-o-meter" in the air.

Leslie Lowe

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