I have a Uno. This is my... maybe 6th project (including LED and LED/Button). I have wired up an LCD and an MMA 7361 accelerometer (ultimately from Pololu http://www.pololu.com/catalog/product/1246
). The LCD runs off the Uno's 5V pin, and the accelerometer off the 3.3V. I am reading from analog pins A0-A2 for x,y,z (they are not scaled for 3.3v)
Things seem fine except:
the z Axis analogRead() (runs from 137 (upside down) to 447 - giving a mid point (ie 0g) of 292 - about 1.43V (should be 1.65 = 3.3/2) giving about 712 mV per g - outside the 740 minimum in the data sheet...
however, the x and y axes are zeroing around 335 (1.64v) - there is a little variance in the x and y
Ideas on what is going on?
Is this variation normal? ie Do I just calibrate manually for each axis or is this abnormal (maybe I've hooked it up wrong somewhere or the chip is a dud?)
The readings are not affected by the LCD being unplugged.
Thanks in advance