On Wednesday 24 August 2016 15:10:58 Dave Cole wrote: > On 8/24/2016 1:02 PM, Gene Heskett wrote: > > On Wednesday 24 August 2016 12:39:39 Jon Elson wrote: > >> On 08/23/2016 10:22 PM, Gene Heskett wrote: > >>> On Tuesday 23 August 2016 22:13:55 Jon Elson wrote: > >>>> On 08/23/2016 04:09 PM, Gene Heskett wrote: > >>>>> On Tuesday 23 August 2016 06:55:03 andy pugh wrote: > >>>>>> For gear tooth detection you probably want > >>>>>> http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570. > >>>>>>l1 31 3.T R0.TRC0.H0.XATS667.TRS0&_nkw=ATS667&_sacat=0 > >>>>> > >>>>> 10 ordered, I'll figure out something to use the others for. 3 > >>>>> for gear sensors and 6 for home & limits, leaves a spare. I'll > >>>>> need to cobble up an index somehow. > >>>> > >>>> The ATS667 is a sensor to detect the passage of a gear > >>>> tooth. It really is not designed as a proximity sensor. It > >>>> will detect a ferrous item passing across the face of the > >>>> sensor, but then stays in that state. If you check the > >>>> datasheet, it has two sensors close together, compares the > >>>> signal from them and sets a flip-flop for which one has more > >>>> signal. So, it is designed to sense an object moving ACROSS > >>>> the face of the sensor. > >>>> > >>>> Jon > >>> > >>> So if we want to use it as home or limit, we should trip on the > >>> far side of what we have passed? > >>> > >>> What occurs when it has come back from there? Or is at a great > >>> distance from the trip generator? Or am I back to 59 cent roller > >>> microswitches? I must admit, they do seem to be doing a quite > >>> repeatable job where I've used them in essentially dry circuits. > >> > >> OK, so when a ferrous object passes left-to-right across the > >> sensor, the output goes high, and then holds. > >> When the object passes right-to-left, then the output goes > >> low, and holds. > > > > That would work for either limits or homeing I think. I have my > > microswitches set so whatever trips them can pass by, but it quite a > > ways before the lever would open the switch again. > > > >> The FF holds the state until the object > >> comes back within range. > >> > >> There most certainly are Hall sensors that detect the > >> presence of an object, without the latching or directional > >> features. I think that is really what you want. Also, > >> sensors that have big magnets in them are not ideal in metal > >> cutting machines. They are fine inside the head of my mill > >> where chips shouldn't be able to get. > > > > There is that too. I have enough trouble with residual magnetism in > > my hand tools as is, those that can approach a motor in particular. > > The motor on my toy mill? I could remove it from the mill and stick > > it to a tin plate decorative ceiling and not worry about its falling > > unless the Richter scale is above 6.5. And tool that approaches the > > nearby drawbar bolt is instantly grabbed. PITA. > > > >> Jon > > > > I found the parts list for the Sheldon and that gear I want to drive > > the spindle encoder with has 60 teeth. Thats 240 edges, similar to > > my optical's I've made before. But while I can envision a 1/2" wide > > alu bar cut in the curve of the tooth OD, with pockets for the > > 667's, I've not decided where I drill holes to mount the alu piece. > > Its a tight fit. > > > > Cheers, Gene Heskett > > Gene, > My experience with standard prox sensors is that they are plenty > accurate enough for homing and limits especially when you are using a > the two approach method which is a rapid approach and then a second > slowdown approach. By doing that I can get single digit thousandths > accuracy for homing which is fine for most automation jobs. Combine > that with Index homing and you are all set for CNC machine work. > Prox sensors are great in that they don't have a magnet in them so > they don't attract chips and most are oil and coolant proof. There > was a company selling oil proof proxes for less than $10 each in the > US. Here they are: > http://www.ezautomation.net/ezvizprox/ezvizprox_products.php?cat=290 > I have never used their sensors so YMMV. There is a big difference > between a shielded prox and an unshielded prox. In most cases you > will want to use a shielded prox. (the plastic doesn't stick out the > end of it.) Automation Direct is a good source of prox sensors. > They also have a generous return policy. > > Dave > Well, I have 2 different versions of the other coming, so we'll do some testing when the arrive.
Thanks Dave. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
