On 03/09/2016 11:38 AM, andy pugh wrote: > On 9 March 2016 at 16:54, <sa...@empirescreen.com> wrote: >> The issue is that we drilled about a .130 hole for the index but it acts >> odd. If you rotate the spindle one direction it will pass the index and >> stay high until it passes the hole then you get a little index pulse low. >> If you run it the other direction it goes low after passing the index - and >> you get a positive index pulse at every passing of the hole. > This may be the internal logic at work. The sensors are rated to zero > speed, and I think have an internal offsetting circuit. However I > can't see how it can tell which way the gear is turning unless it has > two sensors. > Some automotive sensors do actively sense direction, and send a > different pulse length in one direction compared to the other to > encode the direction on a single wire. > The sensors I used (Allegro ATS667LSGTN-T) have indeed, two Hall sensors separated by a mm or two, and a FF that flips one way when sensor 1 has more signal than sensor 2, and flips the other way when that condition is reversed. (I think, maybe check the data sheet on your sensor to be sure how YOURS works.) This reliably detects the passing of a gear tooth. It does have the side effect of showing a reversed polarity when run the other direction. My encoder counter treats the index signal as edge-triggered, so it won't have random alignment if the index is high most of the cycle. Some other interface boards may not work like that.
It shouldn't matter, as the sensor is only used once at the beginning of the spindle-synched move. if your encoder counter DOES act in a level-triggered manner, you would have to add a one-shot to detect the rising edge of the index pulse. Jon ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785111&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
