On Mon, 2009-10-12 at 17:40 -0500, Hubert Bahr wrote: ... snip > I am guessing if I provide slots of uniform presence and > absence of material around the periphery of a disk this will give my the > 50% duty cycle. Then if I set two detectors in a relationship where one > is offset from the other half a slot away this provides a method of > detecting 4 transitions per slot instead of just two. And then the > relationship of the highs and lows determines direction. A third > detector senses a single slot/hole elsewhere that rotates in a constant > relationship with the other slots.
Here is an example of a shop made encoder: http://www.wallacecompany.com/machine_shop/Shizuoka/mpg_proto-1a.jpg This could easily be adapted to a spindle shaft. The disk was milled so in the X-Y plane so a rotary axis was not needed, just a standard CNC mill and .063" end mill. > I think I am approaching the limits > of the number of pins available from a parallel port for a 4 Axis mill. > The number of slots to use is a trade off between desired/necessary > resolution. Its easy to add a PCI parallel port card, even if you have a variety of different controllers. > What resolution is required for tapping? Isn't the > starting edge of an index pulse sufficient, or do they need to track > loading on the spindle? > > Hubert ...snip For electronically geared g-codes, such as rigid tapping, single point threading, cutting helices, the more resolution the better. With a parallel port software encoder counter, there is a limit to how fast the software can count. For measuring just spindle speed, an index may be enough. For electronic gearing 100 to 200 pulses (25 to 50 lines) per revolution seems to be normal. The encoder above is a 100 ppr encoder. For a disk like the one above, a second disk can be used for the index. Lawrence Glaister has a good write up on his encoder: http://members.shaw.ca/swstuff/spindle-encoder.html -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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
