HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 31, 2010, 02:52 PM
York Electronics
Gary Warner's Avatar
Dallas Tx USA
Joined Apr 1999
2,505 Posts
Discussion
Rotational sensing - Analog Hall Sensor - Check me

I 'know' about analog hall sensors, but I've never played with them. I'm reading the rotation angle of a shaft (+/- 30 deg.).

I'm using a ring magnet that's magnetized diametrically (not on it's axis) and slid onto the shaft. I'm placing the hall sensor on the side next to the magnet. Sensor setup in bipolar output.

Is this right? I'm not sure.

Hall Sensor:
http://www.analog.com/static/importe...ts/AD22151.pdf

Magnet:
http://www.kjmagnetics.com/proddetail.asp?prod=R424DIA
Gary Warner is offline Find More Posts by Gary Warner
Last edited by Gary Warner; Dec 31, 2010 at 03:08 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 31, 2010, 04:50 PM
Registered User
Ohio
Joined Nov 2003
1,655 Posts
The chips have a "sense path", you have to supply lines of flux that are
aligned, or it won't see the magnet. Just hook one up to a dc source and
load R, and move the magnet by it different ways, to see what turns it on. Radial is more complicated.
Not sure.
jglenn is offline Find More Posts by jglenn
Reply With Quote
Old Dec 31, 2010, 04:54 PM
Registered User
mudville
Joined Nov 2002
952 Posts
Sounds right.

in bipoler mode, the sensor output should go from Vcc/2 when neither pole is pointed at the magnet, to closer to Vcc when one pole is closer, and closer to zero when the other pole is closer.

To get an unambigous reading, the magnets travel should be limited between the poles..
, not from one side of a pole to the other side of the same pole....

HTH

SteveH
shoutchen is offline Find More Posts by shoutchen
Reply With Quote
Old Jan 02, 2011, 07:58 PM
Registered User
UK
Joined Sep 2005
298 Posts
Presumably you can only measure 0 to 180 degrees like this? So good for total rotations, but not absolute position.
MatC is offline Find More Posts by MatC
Reply With Quote
Old Jan 02, 2011, 08:02 PM
York Electronics
Gary Warner's Avatar
Dallas Tx USA
Joined Apr 1999
2,505 Posts
Thanks guys for the feedback. The hardware will be here in a week and I'll report on how this configuration works. Even 2 EE's that are my friends can't agree on whether or not this configuration is what I want?

Anywho, I have the sensor vane made and all I need now is the Hall IC and magnet. Past that, a few thousand lines of code and I'm in business!
Gary Warner is offline Find More Posts by Gary Warner
Reply With Quote
Old Jan 02, 2011, 08:24 PM
Registered User
Ohio
Joined Nov 2003
1,655 Posts
You might try sim software, probably expensive.

http://www.google.com/images?hl=en&e...iw=790&bih=342
jglenn is offline Find More Posts by jglenn
Reply With Quote
Old Jan 02, 2011, 09:14 PM
Registered User
UK
Joined Sep 2005
298 Posts
I think you'll need two sensors to measure absolute orientation ..
MatC is offline Find More Posts by MatC
Reply With Quote
Old Jan 03, 2011, 10:53 AM
Registered User
mudville
Joined Nov 2002
952 Posts
Maybe I misunderstood, can hte shaft freely rotate, or is the travel limited to +-30 degrees?

If limited to +- 30 degrees,
This seems to be the same application as in hobby servos like a falcon..
Only one sensor is need if you need to read +- 30 degress
if you orient the magnet correctly when the angle is zero..


SteveH
shoutchen is offline Find More Posts by shoutchen
Reply With Quote
Old Jan 03, 2011, 11:05 AM
York Electronics
Gary Warner's Avatar
Dallas Tx USA
Joined Apr 1999
2,505 Posts
Yes Steve, it's an AoA sensor and the rotation will be limited, most likely from -20 degrees to +30 degrees.
Gary Warner is offline Find More Posts by Gary Warner
Reply With Quote
Old Jan 03, 2011, 11:11 AM
Registered User
Dan Baldwin's Avatar
United States, CA, Norwalk
Joined Apr 2004
2,709 Posts
I did something very similar to what you are trying to do with a web unwind system. I needed to be able to sense the position of a "dancer" arm to about +- 30 deg. I used a hall effect sensor (mouser #785-ss495a1) and a cylindrical magnet that was magnetized on the end (McMaster Carr #5688k52 see picture below), and it worked, but I didn't have as much output as I wanted, so I ended up putting 2 magnets facing each other with the hall effect sensor in the 1/8" gap between them, and output was okay. The magnets were oriented with north pole of one facing the south pole of the other.

Dan
Dan Baldwin is offline Find More Posts by Dan Baldwin
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Building a EXI 450, Double check me please. cInfidel 3D Electric Heli Flying 7 Dec 28, 2010 10:28 AM
Discussion High Current Hall Sensor magudaman DIY Electronics 3 Dec 18, 2010 02:19 PM
Discussion hall sensor nitrah60 Engines 8 Dec 11, 2010 07:55 AM
Discussion Hall Sensor upgrades? EddieO Electric Motor Design and Construction 14 Nov 09, 2010 11:47 PM
Discussion Rotational Rate Sensor for Motor RPM bolarobric Electric Plane Talk 3 Jan 17, 2007 05:40 PM