iso9001 said:
Accelerometer wont work. Need somthing sort of absolute since it wont always be on.
Oh yeah!
An extract from the link I quoted earlier.
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THEORY OF OPERATION
The ADXL202E is a complete, dual-axis acceleration measurement
system on a single monolithic IC. It contains a polysilicon surfacemicromachined
sensor and signal conditioning circuitry to implement
an open loop acceleration measurement architecture. For
each axis, an output circuit converts the analog signal to a duty
cycle modulated (DCM) digital signal that can be decoded with
a counter/timer port on a microprocessor. The ADXL202E is
capable of measuring both positive and negative accelerations to
at least ±2 g. The accelerometer can measure static acceleration
forces such as gravity, allowing it to be used as a tilt sensor.
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JimB