On Saturday 24 November 2012 00:21:24 andy pugh did opine: > On 23 November 2012 14:26, Gene Heskett <ghesk...@wdtv.com> wrote: > >> The target wheels we have on our engines are _not_ ferrous. They are > >> a magnetic track and the crank sensor has no internal magnet. > >> (I can't find that actual sensor on the Allegro site). > > > > For a hall sensor to work, there must be a magnetic field for it to > > sense. > > Yes, there is a ring of non-ferrous magnetic plastic stuff (like very > thick cassette tape) round the periphery.
That is on the bottom disks edge in that pix? I wondered about that, not exactly the right color for freshly made metal. > Basically just like this stuff: > http://www.machine-dro.co.uk/high-accuracy-magnetic-linear-tape.html > But applied to the disc prior to the the pattern being applied. > > > Not all steels are magnetic though > > Yes, I know. I have a PhD in ferrous metallurgy. Better than my degree from UHK, and certainly 40 years fresher. But the technology does move on and and I wouldn't want to be 'caught out' anymore than you would. Discussion refreshes memories. Particularly mine. :D > > I've lost interest. Everyone with an opinon seems to think this is a > bad idea. I have no need for it, so I won't bother. I wasn't trying to say it was a bad idea Andy, on the contrary I believe it can be made to work quit well with an additional index detector channel. Half a cmos 556 (7556) set for about a 65 u-sec pulse triggered by the leading edge, and a latch to latch the falling edges state and in should be 100% ready to a simple sampling circuit to grab the resultant dir output of the latch. Seems pretty simple, and possibly less error prone than the quadrature decoder we have already. 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! I can hire one half of the working class to kill the other half. -- Jay Gould ------------------------------------------------------------------------------ Monitor your physical, virtual and cloud infrastructure from a single web console. Get in-depth insight into apps, servers, databases, vmware, SAP, cloud infrastructure, etc. Download 30-day Free Trial. Pricing starts from $795 for 25 servers or applications! http://p.sf.net/sfu/zoho_dev2dev_nov _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
