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setting up a reflective object sensor for dummy's
« on: January 20, 2008, 11:17:43 AM »
hello everybody. I know many people have posted about this before but I cant seem to find all the info Im looking for in one place. Ifinally got my fairchild reflective object sensor hooked up and I can get a signal to the controller. but from there Im lost. first off my original idea to take a peice of foil tape, mask off a strip of it and paint the rest black and wrap it around the inside spindle shaft, doesnt seem to be yielding results. I cant get a stable signal meaning that in the diagnostic screen my index LED is always blinking rather than staying solid on. I can get it to stay off. when I get it as best I can and turn the spindle on Im getting severly fluctuating and crazy spindle speed numbers. The Mach PDF gives all of one paragraph on how to set this up. so my starter questions are as follows.
- what is every body else using for there reflective material and where are they mounting it?
- what adjustment settings are there in mach to set up the spindle once I get a steady signal?
- and what problems should I be looking out for?
I almost feel like someone should have written a catch all piece of literature to cover this topic by now so if it exist please point the way.
Chris

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Re: setting up a reflective object sensor for dummy's
« Reply #1 on: January 20, 2008, 11:39:06 AM »
You said you are wrapping the reflective tape around the spindle, is this correct? if so thats your problem, you only want a bit of tape there so the reflective tape is only seen on part of a revolution and as such the switch is triggered. If you have the tape right round then the switch will continually see it and thus not react properly.
Hood
Re: setting up a reflective object sensor for dummy's
« Reply #2 on: January 20, 2008, 01:01:54 PM »
no you misunderstood. I used a peice of foil tape all the way around the spindle, but I painted it all black with the exception of a thin strip. so only a small line is reflective. though I really cant seem to get the sensor to function properly at all. basicly it doesnt matter what I put in front of it, It will see it. I tried a black piece of mat board and everything. switch goes on when anything is in front of it switch goes off when nothing is in front of it. no matter how reflective or non reflective. also when the switch is on, say if I put a shiny piece of aluminum in front of it, on the diagnostic screen the index LED is not solidly on like It should be. It blinks irraticly. ( Ive also tried a diiferent sensor with same results)
can someone give me a run down of all the things I have to do, to set up the software for an index sensor because I feel like Im missing something. I set up the input under ports and pins.
I looked at the spindle set up screen but it wont even allow me to enter the number of pulses per revolution in the box. Also I have no idea what the other 3 values marked as P,I,D, are for. I assume they control the accel and deceleration but Im not sure, can anyone clear this up for me. Is there another setup screen  need to know about? I'm really in the weeds here.

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Re: setting up a reflective object sensor for dummy's
« Reply #3 on: January 20, 2008, 01:23:16 PM »
If you want to use these settings I think you will need to use the Timing Input rather than the Index one. However it sounds like your hardware is the problem, I dont have any experience with reflective switches as I just use optical ones, maybe Jim will chime in as I think he uses the same ones as you.
 One seting you could try is increasing the Index debounce.
Hood
Re: setting up a reflective object sensor for dummy's
« Reply #4 on: January 20, 2008, 01:54:58 PM »
well Im open to trying the optical switches. can you give me a link to where I cn buy one.
Chris

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Re: setting up a reflective object sensor for dummy's
« Reply #5 on: January 20, 2008, 02:19:13 PM »
You will need a slotted disc to use the optical switch, I also use them for limit switches on my mill, they are deadly accurate. I am in the UK and I got mine from R S Components, if you go to rswww.com then put 455-0919 in the search box you should come up with the switch I have. You will also need a 22Ohm resistor so you dont blow the switches LED but thats all you will need. Heres a pic of the setup on my mill.
Re: setting up a reflective object sensor for dummy's
« Reply #6 on: January 20, 2008, 05:27:24 PM »
I used a sensor like that for the tach on my spindle.  It worked right off the bat for me.  I think it might be a focus thing.  I aimed mine at a hex nut that I had painted flat black then put a bit of aluminum tape on each of the flats.  It was very sensitive to the focal length.  Once I got it adjusted to the right distance, it worked fine.

I think your round shaft may be the problem.  Try putting your shiny bit on something raised so it has a different focal length.

I use optical switches for my home and limit switches as well.  They only have a .005 aperture but I've still never gotten better that plus or minus a thou on homing repeatability from day to day.  If I need it any closer than .002, I just use the homing to rough it in then indicate the part.

Cheers,
Walt

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Re: setting up a reflective object sensor for dummy's
« Reply #7 on: January 20, 2008, 05:47:17 PM »
Walt
 I find that strange regarding your limits, when I first set mine up it was on a manual Bridgeport that I converted, it still had a DRO on it. I did a test by homing and then zeroeing all axis on the DRO, I then moved off and homed again, I did this 100 times and there was only once or possibly twice (it was 3yrs ago so I cant remember) that the DRO didnt read 0.000 and out of the once or twice it was off it read 0.005 and that is mm not inches ;)

Hood
Re: setting up a reflective object sensor for dummy's
« Reply #8 on: January 20, 2008, 06:27:00 PM »
Yup, I was totally shocked.  I thought that .0005 aperture would make them even more accurate than they usually are.
It's on a Taig so it's not like inertia is affecting it.  With the ball screws I have it it right now, the machine is accurate to .0002 over it's entire envelope and usually repeats to .0001.  But I don't count on those home positions.

 I don't keep it as clean as I should.  Doesn't take much dirt to put you off a couple thou so maybe that's it.  I don't worry about it, I just double check everything if I need the accuracy.

Cheers,
Walt

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Re: setting up a reflective object sensor for dummy's
« Reply #9 on: January 20, 2008, 06:37:27 PM »
Walt that could be it, the switches I used at first were ones from homeshopcnc.com. They are enclosed and have a plunger that actuates them by moving a flag out of the optical switch. I have since made up similar enclosed ones for the mill I have now as Home Shop dont seem to sell them any more.
Hood