Now I'm a bit confused about unipolar vs bipolar. When my wheel spins, the magnet will pass in front of the sensor (sensor is static, magnet is rotating with the wheel on a spoke) with the same orientation, as it passes, the magnetic field increases, then decreases. With unipolar sensors this should count as a rotation (a rising and decreasing edge at the output pin - of course I'll use just one of the edges at the controller level). On the other hand with bipolar sensors I think I'd need two magnets, one near the other oriented with opposing poles towards the sensor, one would make it go high and the opposing pole from the second magnet passing by would make the signal go low, am I understanding this correctly?
Now for the sensitivity of the sensors. Let's assume, for the sake of the argument, a typical fridge magnet at 5mT as per Wikipedia.
With the unipolar versions of the sensors with the TLE4905 (page 8 of the data sheet linked above) the strength of the magnet would not be enough to trigger the sensor which has a
The TLE4906 is a bit more sensitive at
Bop=6.5mT, but still not enough.
Is this right? Now I either need a stronger magnet or a more sensitive unipolar sensor, right? If I got the unipolar vs bipolar part right, then the answer should be yes, otherwise I need some explanation on why not.