On Wednesday 14 October 2009, cogoman wrote: >|Another option I have considered, is to use Hall sensors which would >|work okay without an enclosure, but I seem to recall that Hall sensors >|are not very fast, though engine crankshaft sensors seem to work well >|enough. > >Here is a new encoder option on the market that looks very attractive, the: > > > AS5040 > 10Bit 360° Programmable Magnetic Rotary Encoder > >These are chips with hall sensing of a single magnet positioned over the >chip. this one gives 10 bit resolution and in the quadrature mode has >this to say about speed: The incremental outputs are not affected by >rotational speed restrictions due to the implemented interpolator. The >incremental output signals may be used for high-speed applications with >rotational speeds of up to 30,000 rpm without missing pulses. There is a >delay from the actual position change to the time it is reported, but it >looks like it could follow a 1500 RPM motor without interpolating, and >if used with a spindle at constant speed, since you're looking for the >index pulse to line up at the same spot every time for threading, it >might work for that application too, as long as you didn't have to sync >up the thread start with some feature cut at low speeds. Some of the >chips in this series are available from component distributors for >around $10 each in onesies, and I remember seeing the magnet specific to >this application for sale also. There is a company that has put out an >encoder using the AS5040 at this link: >http://nubotics.com/products/me110/index.html > While that item is neat, its rev limit of 240 rpm because of the ABS bearing and a .125" shaft would seem to relegate it to the hobbiest rc model controller market. It also needs programming at least once, or perhaps at power up each time. So while nice, it would only be suitable for proof of concept, not the production floor. That same chip and magnet, mounted in a decent housing with a pair of ball bearings (steer clear of the skate wheel bearing, its used as blade guide bearings on my new bandsaw, and at bandsaw blade induced rpms, chatter to beat hell, which prints into the cut, so their price for a tube of 1...@$4.50 reflects that quality and they WILL be changed) would begin to make it pretty attractive.
That is not to say that _we_ couldn't make one using that same chip and magnet, that would be quite serviceable, for instance by fitting a plastic gear of the same pitch and tooth count as the spindle gear in an x1 mill so it follows the spindle on a 1/1 basis. Or the same idea in the head of a 7x12 lathe, but that would require an extra slot cut in the end cover, and a new, cover the gear cover made. I would assume the chip maker could give us the mechanical specs, but AI haven't googled that yet. -- 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) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> If you notice that a person is deceiving you, they must not be deceiving you very well. ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
