Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: jonny quest on January 30, 2013, 03:03:10 PM
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I'm using latest version of Mach... when machine sits idle for a few minutes I need to reset because it says limit switch has been triggered.
Is this normal... or is there a way to see what switch has been triggered to see if I have a faulty switch?
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It sounds like you might be picking up noise. Do you have a value in your Debounce setting in General config (top right corner)?
Brett
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Debounce interval is set to 5000 x 40us, index debounce is 500.
This machine has never done this before... just started doing it. Only change has been updating to newest Mach version... and lowering Kernel speed to 35000, from 45000 to help with some suspected missed steps in my Z which seems to be fine so far.
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Was the debounce set to 5000 before this problem or did you just change it?
Brett
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I haven't changed it, and I don't know what it was at.
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5000 is high. If it had to be that high before to prevent the false triggers, I would try to eliminate that. I'm not saying you don't have something else going on like a flaky switch or something, but will be hard to find if dealing with noise issues as well. How are your limits wired to Mach? Are they all on a single input or does each have their own?
Brett
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Jonny, I meant to also tell you that many things can effect noise including temperature, humidity, etc. Even light bulbs. It can be a pain to get sorted but usually proper switches and shielded wires with proper grounding are the first line of defense. Also, here is a link that may help you.
http://www.machsupport.com/forum/index.php/topic,21908.msg152243.html#msg152243
Brett
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I fixed the problem. I restarted Mach.
Uggghhh, that's frustrating.
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It's doing it again after machine is turned on for a couple of hours. Everything is fine... then it triggers a limit switch like every 5 minutes.
If I reboot computer, it's good for another 2 hours or so... then repeats problem.
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Have you opened the controller to see if any and or what grounding practices are being used? Start there and then work on cleaning up the problem. I promise fear of starting is much worse than solving it.
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I bought an oscilliscope. Where would the best place to look for noise be? I have a 2 channel model. where would I hook up the scope leads?
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Electrical noise is generally one or a series of relatively high amplitude and very fast spikes appearing on an input to the BOB or controller. These spikes are often so fast that it requires a pretty high quality scope to be able to spot them so don’t be surprised if you find nothing. Scope probe connects to an Input and it’s Screen to GND. Measurements should be taken whilst the machine is in operation so take care.
The best bet with electrical noise problems is to fit miniature 0.1uF capacitors (one connected between each used Switch Input and GND) at the controller / breakout board end.
Tweakie.
Addition; Just a suggestion but another thing that has caused problems is the Watchdog Timer – Config / General Config – Make sure ‘Use WatchDogs’ is unchecked.