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Topic: Angular position sensor? (Read 6 times) previous topic - next topic

AWOL

Quote
it senses speed.

No, it senses magnetic fields.

You need a shaft encoder.
I don't know of any solid-state ones, so a Gray code encoder is probably the only sensible absolute position sensor.
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louarnold


Quote
it senses speed.

No, it senses magnetic fields.

You need a shaft encoder.
I don't know of any solid-state ones, so a Gray code encoder is probably the only sensible absolute position sensor.

OK. I'll keep my eyes open.
Thanks very much.

johnwasser

You have not said what kind of resolution you need. 

Austria Microsystems makes the Hall Effect absolute encoders in 8, 10, 12, an d 14 bit resolution (256, 1024, 4096, 16384 steps):

          http://www.ams.com/eng/Products/Magnetic-Encoders/Rotary-Encoders

DigiKey has the AS5263 (12-bit) for $10.22 each: http://www.digikey.com/product-detail/en/AS5263-HQFT/AS5263-HQFTCT-ND/3028680
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louarnold

#8
Jul 17, 2012, 08:48 pm Last Edit: Jul 17, 2012, 08:58 pm by louarnold Reason: 1

You have not said what kind of resolution you need.  

Austria Microsystems makes the Hall Effect absolute encoders in 8, 10, 12, an d 14 bit resolution (256, 1024, 4096, 16384 steps):

         http://www.ams.com/eng/Products/Magnetic-Encoders/Rotary-Encoders

DigiKey has the AS5263 (12-bit) for $10.22 each: http://www.digikey.com/product-detail/en/AS5263-HQFT/AS5263-HQFTCT-ND/3028680

Ahhh, that's a good question.  I'm not really sure about angular resolution. Placing a gear around a steering shaft and using a stepping-motor driven worm gear, what would be a realistic resolution? Would 1 degree be enough? I wonder.

The sources are good. I'll have to look at them more closely, but now I know that they really exist, so thanks very much. I note they seem to be ICs. How do they connect to a shaft?

Can a hall-effect device be made to sense angular position without having rotation - so that when the device powers up, it knows what direction the single tire steering wheel is pointing?

johnwasser

> Placing a gear around a steering shaft and using a stepping-motor driven worm gear, what would be a realistic resolution?

If your stepper does 200 steps per revolution and your worm gear has 100 teeth that is 20,000 positions.  Perhaps you would be happy with 4096 positions.

> How do they connect to a shaft?

Magnet on END of shaft.  IC centered over magnet.

> Can a hall-effect device be made to sense angular position without having rotation - so that when the device powers up, it knows what direction the single tire steering wheel is pointing?

Yes.  That's why they are called ABSOLUTE angular encoders.  They tell you absolutely which way the shaft is pointing.
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