How to choose a hall sensor?

[Kirill]

Hi everyone!

How to choose a hall sensor?
I have a MAC 8T hub motor.
SS41 it’s a size. But what should be the rest of the parameters?

 

[hias9]

SS41 is not a size, it's a model by Honeywell. The size would be the measurements of TO92 package.
The sensors should be TO-92 package, digital, bipolar, should work with 5V input voltage and should have a max. operating temperature of 150 (or higher) degrees celsius.

 

[Bradz estuff]

Does it even make a differance what hall sensors you install?
From motors I've done it doesn't seem to as long as they are all the same type they seem to work fine

 

[amberwolf]

Does it even make a differance what hall sensors you install?

Yes. Typical ebike/etc motor controllers that use three hall sensors for position info are looking for a digital output that grounds itself when active, and is open-circuit when not active. That's usually called OC or open-collector output.

There are many kinds of hall sensors, including analog ones (which won't typically produce antyhing like the required output signal), and digital ones that output a voltage rather than just grounding the output, etc.

There are also latching output, which keep the output active (grounded, in the case of typical motor halls) once activated, until the opposite polarity magnetic field is detected, and then they turn off. Some controllers with high ERPM motors may work better with these because it halves the number of detected pole transitions vs sensors with nonlatching outputs.

The other common type in motors (and hall type brake levers, speed sensors, etc) is the non-latching type, which simply turns on the output (grounding it instead of leaving it open circuit) whenever the magnetic field strength is high enough (regardless of polarity).


Most controllers will work with either latching or non-latching digital output halls with OC (open collector) outputs.

The most commonly used are some version of Honeywell SS41 or SS411, or a clone thereof. As long as it has that same functionality, has a VCC rating within the voltage supplied to the motor for hall power (mostly 5v, with some 12v), and has open-collector signal pin with max signal pin input voltage (for pullup resistor inside controller) of whatever that controller uses (mostly 5v, with some 12v), it will probably work.

Any other type...you'd have to test it with the specific motor and controller combination and report back.

 

[Comrade]

There are many kinds of hall sensors, including analog ones (which won't typically produce antyhing like the required output signal), and digital ones that output a voltage rather than just grounding the output, etc.

From what I know, the proper name for "analog ones" is linear, and latching for "digital ones".

There are also latching output, which keep the output active (grounded, in the case of typical motor halls) once activated, until the opposite polarity magnetic field is detected, and then they turn off.

Latching means there is a specific Gauss strength they need to latch "on" and a specific Gauss strength to latch "off".

So a hall sensor that might work well in this context would latch at say 100 and release at say 50. So it will produce a square wave as the magnet comes closer and then gets too far.

I'm not sure how a glued down magnet would generate an opposite polarity magnetic field.

 

[amberwolf]

From what I know, the proper name for "analog ones" is linear, and latching for "digital ones".

Not all analog ones use a linear output curve. You may read posts or pages that equate them, but they are not exactly the same thing. A linear output sensor is analog output, but an analog output sensor isn't always linear output.

Latching means exactly that--the output latches on once a magnet has activated it (per whatever specifications that specific sensor has. A latching output sensor is generally a digital output sensor too (I haven't worked with any analog output latching ones yet), but a digital output sensor is not always latching.

Latching means there is a specific Gauss strength they need to latch "on" and a specific Gauss strength to latch "off".

Depends on the sensor. The ones used in motors for this purpose use an opposing polarity, not just a specific strength (though they require that, too). One page that explains more about their latching sensors:
https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/latching-switch-hall-effect-ic-basics

pdf version
https://www.allegromicro.com/-/media/files/application-notes/an296067-latching-switch-hall-effect-ic-basics.ashx

They have other documents talking about their other types:
https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/unipolar-hall-effect-sensor-ic-basics

https://www.allegromicro.com/en/products/sense/switches-and-latches/micropower-switches-latches

https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/bipolar-switch-hall-effect-ics

So a hall sensor that might work well in this context would latch at say 100 and release at say 50. So it will produce a square wave as the magnet comes closer and then gets too far.

That sounds more like a Bipolar sensor.
https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/bipolar-switch-hall-effect-ics

I'm not sure how a glued down magnet would generate an opposite polarity magnetic field.

The magnets in a typical BLDC motor are installed in alternating polarities. Other motor types may also be. You'd have to check any specific motor you are working with. (use a magnet you know to be polarized in a specific way, and see which magnet faces repel it and which attract it (don't ge it too close to the magnets under test or you may lose hold of it and it could crack them on impact), or use a magnetic sensor tool that tells you. A tiny compass might work but it may be too swamped by the surrounding fields to flip properly).