[chbot] Unusual sensor

Helmut Walle helmut.walle at gmail.com
Mon Dec 14 10:41:16 GMT 2020

A Hall sensor package should not have epoxy fillings, and the packages of Hall sensors are
usually fairly thin with parallel flat sides, which makes it straightforward to use them in a
geometric configuration where the field to be measured crosses the actual semiconductor
perpendicularly, e.g., with the sensor glued into a slot in a ferrite toroid.

A capstan motor controller on the other hand probably mainly needs to control for speed, and for
that purpose either a tacho generator, or even just a small pick-up coil if the rotor has
alternating permanent magnetic poles that can be detected, or a photo-electric pick-up (IR
emitter-detector pair aimed at a contrast pattern on the rotor) would be suitable. So it could
be a transducer for that latter principle.

Kind regards,

On 14/12/2020 23:00, Martin Towers wrote:
> This looks like something I've seen inside the capstan motors of VCRs.
> That would have been 20 years ago.
> I thought it might be a hall sensor.
> Martin
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