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Author Topic: Spindle speed  (Read 4512 times)

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Offline Kristin D

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Spindle speed
« on: May 14, 2008, 04:58:20 PM »
Just wondering I have a bunch of U shaped opto switches I bought surplus, if I put a disk on my spindle with either a slot or possibly drilled holes will inputing that to Mach provide a RPM readout? I'd go play with the program but it's hot back where it is today and I don't even want to step into the room till later after the sun is off that wall.

Kristin

Offline Hood

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Re: Spindle speed
« Reply #1 on: May 14, 2008, 05:53:30 PM »

Offline Kristin D

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Re: Spindle speed
« Reply #2 on: May 14, 2008, 07:19:17 PM »
So if I install a disk and sensor I can calibrate it to give an RPM readout? Cool, I don't think I can incorporate speed control though as I don't have any documentation on my DC motor controller and it needs to start from zero or it just does not work, I suppose I could cobble up something like a D/A converter to drive the input further down the road.

Thanks,

Kristin

Offline Hood

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Re: Spindle speed
« Reply #3 on: May 14, 2008, 07:21:39 PM »
No need to calibrate it, Mach will see one pulse per rev so it will know what speed you are doing :)
Hood

Offline Kristin D

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Re: Spindle speed
« Reply #4 on: May 14, 2008, 07:28:00 PM »
Thanks, now if it cool's down in the "LAB" I will have to go back and experiment later.

Kristin

Offline Kristin D

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Re: Spindle speed
« Reply #5 on: May 15, 2008, 03:31:42 AM »
Another question, I would rather not have a notch in the disk, could I for instance drill (2) 1/8" holes and file out between them, it would be more user friendly should I lay my hands upon the spinning disk.

Kristin

Offline Hood

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Re: Spindle speed
« Reply #6 on: May 15, 2008, 04:26:52 AM »
You will need more than 1/8" wide or at high speeds Mach may miss it. If you drilled a 3/8" or 7/16" hole and then squared it off with a file it should work fine as long as you get the opto lined up properly.

Offline Kristin D

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Re: Spindle speed
« Reply #7 on: May 15, 2008, 03:07:07 PM »
Well it looks like a 1/8" hole might work for my application, I am running this on a taig lathe probably not going to exceed 3500 RPM, so from the website the slot width or angle is (alpha=.0012xN) or 4.2, so with my 2.5" diameter disk should be (W=.0088x alpha x dia) or .0924, I still may drill 2 holes next to each other and file out between them to increase my capability to say 5000 rpm when I am not using a chuck. Please check my calculations math is NOT my strong point! I just didn't want to make a finger remover by making open slots which is why I am looking at keeping this compact and using drilled and filed holes.

Offline Hood

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Re: Spindle speed
« Reply #8 on: May 15, 2008, 03:10:28 PM »
Try with that size and if you have problems make it bigger, some people get away with smaller slots than others, I suppose there are many factors that come into play. I have always made the slots approx 3/8" wide and never had a problem so thats why I suggested it.
 Be sure to let us know how it works out
Hood

Offline Kristin D

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Re: Spindle speed
« Reply #9 on: May 15, 2008, 05:31:40 PM »
Wondering about powering this up, I have a USB cord from another project and was thinking (dangerous unto itself) that would be a safe place to get the +5 VDC for the LED in the opto and also either ground or +5 for the input without worring about floating grounds between supplies, I don't want to take anything off the controler board and let out the magic smoke. Do I need a resistor in series with the photo transistor going into the LPT port or can I just wire it directly. I will use a 220 Ohm 1/4 w for the LED and am planning on doing a comb test, running a hair comb through the sensor to see what is going on before mounting it to the machine.

Kristin