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limit switch triggered
« on: February 22, 2013, 07:21:05 AM »
Hi Its me again, I still get the occasional program stopping because Mach tells me a limit switch has been triggered although non of the warning on the diagnostics page show any faults. I have rechecked and earthed the machine, BOB and spindle drive board, shielded the wires, set the debounce on several occasions, changed the computer and checked the switches but I still get the machine stopping once a day. Luckily the stop is instant so no damage or cutter breakage has occurred. My questions is in the general config page there is a tick box to "use WatchDogs" if I unticked this box will it stop the limit switch signal stopping the program, or is it unwise to do so as it removes the overtravel limits and other protection systems. Or has it nothing to do with my problem. Jim   

Offline Hood

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Re: limit switch triggered
« Reply #1 on: February 22, 2013, 07:50:21 AM »
If the message you get is Watchdog triggered then disable it, if not then its unlikely to help but wont do any harm disabling.
Regarding not seeing the LEDs on the diagnostics page, that is normal with noise issues as they are so quick the screen does not have time to react due to the screen refresh but the driver sees them as it is fast.
Hood

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Re: limit switch triggered
« Reply #2 on: February 22, 2013, 07:53:33 AM »
BTW that is why Industry uses 24v for signal wiring, very resistant to noise due to the big difference between a high and low signal threshold. I am glad to see at least one company has seen the benefits of 24v I/O as it makes my life a lot easier as I dont have to have extra interfaces to convert the 24 to 5 and vice versa.
Hood
Re: limit switch triggered
« Reply #3 on: February 22, 2013, 08:09:15 AM »
Cheers Hood whats got me baffled is the machine has been working fine for some 3 years, so whats got into it is beyond me. You can see from my previous threads I think I have solved it only for it to return a couple of days later. I'm running on the latest Mach software since my computer failure early this year. Is it worth going back to the older version, I must have it on a disc somewhere or am I clutching at straws. Jim

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Re: limit switch triggered
« Reply #4 on: February 22, 2013, 08:35:49 AM »
Could be  something gradually dying, eg a VFD may produce more noise as capacitors start to go.
You could try an older version, I do know there are lots of issues with the latest lockdown and development versions and Turn and I do have at least one issue with them and mill but nothing like limits tripping. You can get older versions on the ftp site if you dont have them.

Hood

Offline Chaoticone

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Re: limit switch triggered
« Reply #5 on: February 22, 2013, 09:06:09 AM »
Jim, it would be easy enough to load an older version just to see if it helps.  I don't think it will, but can't hurt anything to try as long as you back everything up before you do.  Just copy your whole Mach 3 folder and put in on a thumb drive.  As to why it is doing it now after doing for a while you must understand, many things effect EMF.  Humidity being one great example.  Ever slide your socks on the carpet and get a shock when you touched something metal?  The results vary greatly with the relative humidity.  How about rub your hair with a balloon?  That doesn't work if your hair is wet.  Noise can be a real PITA to put it lightly.  I remember a while back a guy had a machine that had been running fine, all of a sudden it started throwing false limit switch triggers.  The problem was he had added a fluorescent light over his machine.  So, what has changed that effects your machine?  

BTW that is why Industry uses 24v for signal wiring, very resistant to noise due to the big difference between a high and low signal threshold. I am glad to see at least one company has seen the benefits of 24v I/O as it makes my life a lot easier as I dont have to have extra interfaces to convert the 24 to 5 and vice versa.
Hood
No truer words have ever been spoken Hood!

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: limit switch triggered
« Reply #6 on: February 22, 2013, 10:45:43 AM »
Thanks for the advice Chaoticone. As I have mentioned in previous forums I have an old 1988 LYNX 80 spindle drive unit, its right next to all the other electronics and looks like something out of an old TV. I have looked at it and I think I could move it into a separate box on the back of the machine. This is a standard metal electrical enclosure and will be about 60cm for all other electronics, is it worth a try our does the interference go down the control wires. Jim

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Re: limit switch triggered
« Reply #7 on: February 22, 2013, 11:47:20 AM »
Jim, it may well be worth trying.  The interference will go down the wires but shielded cables should eliminate the worries of that.  This is why you only attach one end of the shield, at the controller.  You simply cannot eliminate EMF, you can only try to guide it where you want it to go.  What you hope to do is give a path of little resistance to ground and away from your low voltage bits.  Ground loops are like big antennas, they simply distribute the noise all over.  It gives them a path to run around freely wreaking havoc without ever having to go to ground.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: limit switch triggered
« Reply #8 on: February 22, 2013, 02:09:02 PM »
Hi Chaoticone, just looking at my Lynx80 Spindle drive board and thinking about moving it when I noticed a burnt thingy. Its on the 240v power in line (see picture) the first electronic connection on the board. In the manual it says "Diodes D34-D37 form a separate full-wave, fused for motor-field supply. Field circuitry is protected against high field-transients by capacitor C6 and varistor VDR1," it looks as if the capacitor has blown (C6). The spindle drive board works perfectly so don't want to mess unless you thing this could be giving my limit trigger fault?

Offline Hood

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Re: limit switch triggered
« Reply #9 on: February 22, 2013, 02:12:17 PM »
Looks like a RC Network, ie a capacitor and resistor in one package, could well be causing your issues ;)
Hood