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Topic: Understanding hall effect sensors? (Read 112 times) previous topic - next topic

munty-scruntfundle

Hi there.  I posted a question a few days back for finding small linear hall effect sensors.  I've since worked out the sensors are all tiny, it's what they're packaged with that makes the difference.

Anyway, I don't have the brain to read through all the technical documents for these things, they're totally above my pay grade and mental capacity, I'm getting old!!  

So I've ordered a load of different small boards, thankfully none of these things are expensive, sadly I can't get any of them to work properly, except the well known KY-024 which is too big for the application.  It's a shame as the KY-024 gives me the exact range I need and the arduino reports a lovely smooth curve.

With any of the other makes and models I get only high or low, an immediate switch within a fraction of a mm, no ramp at all.  They're all 4 pin boards with a digital and analogue output, yes I'm using the analogue, all the same setup as with the KY but very different results.  

What is it I'm not understanding?  How does an old idiot get around this problem?
Thanks.

munty-scruntfundle

I should add, I have tried loads of different magnets from pretty large to tiny, the only difference is the distance at which the boards switch, I don't get any kind of ramp with any of them.

PerryBebbington

Hello Munty,

As you have not told us what Hall effect sensors you have I'm not sure how you think any of us can help.

My non-helpful generic answer is that if the output is switching from low to high or high to low then you have Hall effect switches, which do exactly that.

MarkT

Hall sensors come in two types, linear and switches.  The switch sort have an internal comparator(s) to
convert the Hall voltage to a logic signal.

You want the linear sort.

If you look at the datasheet for the KY-024 it claims to use the A3141 hall sensor and an opamp,
but the A3141 is a Hall switch, not a linear sensor, so something's a bit fishy there.

Had a quick look and found: https://www.mouser.co.uk/ProductDetail/Melexis/MLX90242LUA-GAA-000-BU/?qs=KuGPmAKtFKWLmpSPshcA%252BA%3D%3D

You have to be careful as a lot of confusion exists between Hall switches and linear Hall sensors on
various websites.  The datasheet is the place to go to check what is what.

You don't need a whole module, that's overkill for a single chip sensor like this that is available as a
simple TO92 3-pin chip.  The only other component needed typically is a decoupling capacitor.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

Ron_Blain

Using a good magnifying glass look at the part numbers on the actual hall effect chips. For example a KY-024 module uses any of several analog sensors but primarily a SS49E (Honeywell). An actual analog sensor. Part of the problem is just because a module says Analog and Digital does not mean the sensor used can do both. If you can read some actual sensor numbers Google them for their data sheets. A true analog sensor data sheet will state so and should reflect a sensitivity such as mV/Gauss. Digital Out units normally reflect a threshold. The pinout on the modules can be deceiving.

Ron  

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