Hard limits trigger when spindle turns on

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bob274
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Joined: Sat May 28, 2016 12:10 am

Hard limits trigger when spindle turns on

Post by bob274 » Fri Jun 03, 2016 8:31 pm

I recently added limit/home switches and a new 500W quiet cut spindle to my Shapeoko. The machine runs and homes fine. But the second I turn the spindle on, even at a very low speed, GRBL registers a hard limit trigger. It even occurred when I powered on the spindle power supply and the spindle wasn't turning.

What I did was run the spindle wires on the complete opposite side of the machine, far from any other wires or the USB cable. The spindle power supply is housed in a separate box. I have a USB cable with two ferrite beads on it. I tried using a filtered power strip, but nothing. I added two ferrite beads to each end of the spindle power cable, and the issue went away when flipping the power supply switch. It still triggers a limit when it starts spinning though.

I have the limit switches all held high with external 10k pull-up resistors. When I measure the switches, they're at 4.95V. When I power on the spindle they drop slightly to 4.91V.

I've read through the wiki suggestions and forum posts, and can't quite find the exact problem I'm having (most have USB connection issues). I've tried some wiki suggestions, but am hesitant to start pouring more money into it to see what may or may not work. Anybody have any ideas for this specific problem? Thanks!!

DRobs86
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Re: Hard limits trigger when spindle turns on

Post by DRobs86 » Sat Jun 04, 2016 4:52 am

Perhaps try to put them on two different circuits in your home. I don't think this is going to fix it, but it's easy to do so at least worth a shot.

WillAdams
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Re: Hard limits trigger when spindle turns on

Post by WillAdams » Sat Jun 04, 2016 10:16 am

My suspicion would be a flaw in the wiring or the board — have you checked it for any sort of flaw which would result in current leaking over to ground?
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

bob274
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Joined: Sat May 28, 2016 12:10 am

Re: Hard limits trigger when spindle turns on

Post by bob274 » Wed Jun 08, 2016 6:40 pm

DRobs86 wrote:Perhaps try to put them on two different circuits in your home. I don't think this is going to fix it, but it's easy to do so at least worth a shot.
Unfortunately I can't. There's only 1 circuit anywhere close by.
WillAdams wrote:My suspicion would be a flaw in the wiring or the board — have you checked it for any sort of flaw which would result in current leaking over to ground?
Can you elaborate on what you mean by a flaw in the wiring or the board?

WillAdams
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Re: Hard limits trigger when spindle turns on

Post by WillAdams » Wed Jun 08, 2016 7:55 pm

Some errant bit of solder on the board which shortens the distance between traces?
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

Picengraver
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Re: Hard limits trigger when spindle turns on

Post by Picengraver » Thu Jun 09, 2016 12:48 am

It is most likley electrical noise. Connect a 0.1uf ceramic capacitor between each limit switch connection and a ground connection on the Arduino board, as close to the board as you can.

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