Re: Hall effect sensor

thomas wrote:
I'd like to use a Hall Effect sensor to detect 6 magnets on the outside of a 2.5" rotating cylinder. It rotates at 20 RPM resulting in 120 pulses per minute (I'll calculate speed from this). This will be a damp environment so a ferrous 'target' is not an option.

I have found small inexpensive ring magnets (with the S pole facing out) that I can easily mount on the cylinder. I have NOT found small inexpensive ring magnets that are magnetized diametrically (N and S are on the same face).

There are many many types of Hall Effect sensors. Most need alternating N and S fields: either with 2 opposite poled magnets, or with a single N/S ring magnet.
Is there a type that can detect the coming and going of just a S field (the field will never be totally absent)?

I found a Gear Tooth Sensor type that senses a ferrous target. Can I just use the S facing ring magnet instead of the ferrous target?


TIA


I think the gear tooth sensor will do just fine.
You can also use any small tranformer,from which you can
remove the iron on one side of the coil.
Unless of course your speed can go to zero, in which case
you need the hall type tooth sensor.
You could also try a reed relay, they have a long lifetime
as long as they only have to switch a small current.
.

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