Electronic – Best sensor for measuring rotation angle

sensor

I've come into an existing design that uses a 2D accelerometer chip to measure a board's rotation angle around a shaft. The board is attached to a motor that drives a gearbox that rotates the shaft, so the motor and board rotate with the shaft. Deriving the angle and calibration of this device is quite complex, is there a simple part out there that say has a high level serial interface that can just tell me the rotation angle? Desired accuracy would be < 1 degree. It's for a solar tracking application so angles are between -85 and 85 degrees, speed of rotation is quite slow.

Thanks if anyone can help,
Fred

Best Answer

Rotary encoder
Optical Encoder
Discrete hall effects at predefined positions (viable if you only need zonal info - BLDC)
Linear hall effect sensors either 2off at quadrature & use atan2( via cordic), or 3off at 120deg displacement and use park&clark.
resolver

I would say for your requirement two optical encoders slightly displaced from one another to increase the angular resolution

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Electronic – Best sensor for breathing activity

Probably a thermistor to look at the temperature change between inhaled and exhaled breath would be easiest. If you're really interested in flow, then a thermistor in self-heating mode to be cooled by inhales and exhales. the latter is trickier, as inhaled and exhaled breath will be two different temps, so the flow sensitivity for each phase will probably be different.

Moving up the line, you can also look at chest inflation using skin plethysmography, which is essentially the broadcasting of a small sin wave, and looking at the reception at a distant location on the chest. The sine wave should really be isolated.

Electronic – L3G4200D Gyro Sensor – Measuring Angle

First, you could use something like this to get your value into a proper signed integer:

uint8_t xl = ...;
uint8_t xh = ...;
int16_t x = *(int8_t *)(&xh);
x *= (1 << 8);
x |= xl;

But x is just a value in Degree per Second. To get your current orientation as angle, you have to integrate this value over time, which will add a lot of drift. To compensate for this, you could then filter it with accelerometer data (PDF!).

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