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
--
"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>
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