On Monday 03 December 2007, Kirk Wallace wrote: >Has anyone tried using a magnetic sensor such as a crankshaft position >sensor for a spindle encoder? I would not have to protect this >arrangement nearly so well as an optical system against oil and dirt. > >Initially, I found this part - AKL001-12E: > >http://www.nve.com/Downloads/gtsensor_catalog.pdf > >The "gear" and bias magnet would be easy to make and mount. I guess the >tricky part is in dealing with the analog nature of the sensor, which >means more than one or two components to wire, but no big deal.
I'd think it would be an ideal solution. The response goes down to DC, and obviously GMR is high speed too as its now being used in the new terrabyte sized disk drives as the read head. There might be a physical problem with the bias fields when attempting to develop an index pulse from an adjacent device, requiring more separation than the usual opto thingy's need though. With a few milliamps through them, any 'analog' problems caused by the strength of the bias field would be absorbed by running them through an lm-339 comparator anyway. Or, with the right current through them and a good bias field, it might be possible to use the output of one side of the bridge as a TTL level signal all by itself. Neat, and probably fairly cheap to boot since the auto industry uses them in 100k quantities. Here is a thought, cannibalize a 5 volt reed relay coil as the bias source, you may be able to use one end of it for the gear teeth, and the other for the index pulse detecting a piece of bailing or even picture hanger wire going by for the index pulse. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Windows is the only solitaire game that requires 16 MB of RAM. ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
