Author Topic: Help with magnetic switch sense range  (Read 178 times)

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Offline Jwillis

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Help with magnetic switch sense range
« on: November 26, 2018, 04:20:33 am »
Before someone says "buy a new fan"I already did  , this is more for curiosity than cost.I burned out a 120mm computer fan by over voltage.So as usual   I decided to take it apart to see how it worked.I checked the 4 coils on the armature and they check good.
The only other piece in the circuit is a magnetic sensor A1421 which is obsolete.This is the part I suspect is faulty.
Now ,as I understand,  the sensor will trip and release as the poles of the cylindrical magnet (S-N-S-N) pass by it which changes the polarity of the armature.Would that be an accurate analysis ?

The only replacement I can find is A1422LK-T but the sensor range is different. as you can see in the link. And don't seem to match the data sheet
The data sheet shows units in Gauss but the sensing range on comparison chart is describe in milliTeslas ..Threw me off a bit but figured it out eventually.  1 Gauss = .0001 Tesla, or 1 Tesla = 10,000 Gauss.Both seem to have the same Operate Point (15.0G)but different Release Point  A1421LK  Is typ 0G and the A1422LK-T is typ -15G
Anyway would that be a problem if I decide to replace the sensor or should I just consider the peak to peak differential of 50G for both and not worry?

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