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During the search for some sensor, I stumbled over the following part (MA477M) and I was wondering how exactly it would be used. It is called "Single Phase Hall Effect Fan Driver". How would this drive a fan, and why does it need to be combined with a hall sensor?

Description from the datasheet

Placing the device in a variable magnetic field, if the magnetic flux density is larger than threshold BOP, the DO is turned to sink and DOB is turned to drive. This output state is held until the magnetic flux density reverses and falls below BRP, then causes DO to be turned to drive and DOB turned to sink

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2 Answers 2

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Probably it needs a fan with a permanent magnet.

A induction motor would need two phases, usually done with a capacitor that shifts the main phase off 90 degrees, then this feeds the aux. phase. Combination of both do produce rotating magnetic field.

Now, with a single phase is almost impossible to spin a rotor, unless using a PM and a stator field that follows the rotor position. However this motor may not have a very high torque at low revs, and it is pulsating. But if used on motor with high inertia and low load torque it could be a valid economic solution.

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It doesn't need to be combined with a hall-sensor; one is included in the package.

Mount the package near the rotating armature, in the presence of magnets which can at least provide +/-20gauss.

As built-in hall sensor detects these magnets passing near it, it reverses the coil polarity, causing the armature to accelerate.

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