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Author Topic: Limit switches  (Read 3522 times)

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Limit switches
« on: November 28, 2008, 10:46:52 AM »
 I have had some problems with my limit switches and seems not an uncommon problem. So by process of elimination I found that if I only use them for homing, they work fine. but when they are used for homing and limit, I get frequent limit trip errors.
 Have not needed my limit switches at this point but may find a need latter as I gain knowledge with experience.

Offline Hood

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Re: Limit switches
« Reply #1 on: November 28, 2008, 11:10:36 AM »
The reason you dont get problems when you use them  for Home only is because you dont have any limits set when you do that. You may find at some time you will get a error when you are homing as the switch will bounce or pickup noise just at the time you are doing the homing as obviously they are still doing so,  just Mach is not constantly monitoring them so you are not noticing.
Re: Limit switches
« Reply #2 on: November 28, 2008, 11:22:28 AM »
Thanks for your input... this sounds very reasonable. because when I am homing I jog close to home...

Offline jimpinder

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Re: Limit switches
« Reply #3 on: November 29, 2008, 06:03:08 AM »
You don't say what switches you are using, but to get over this bounce problem, try replacing them with optical switches of some sort. Mine are laser detectors, fixed at the limits. I have two lasers on the carriage, and when they shine on a detector the detector sends a Ov signal to the computer. The lasers were £10 each and the detectors were in the order of £1 each (possibly less, I can't remember) The beauty about it, there is no big mechanical obstruction on your lathe bed to get wiped out, and you can, if you wish have both homing and limit detectors run by each laser.

The detectors are schmidt trigger types, which give an instantaneous signal (no bounce), and I find the accuracy very good, even with cheap non-focused lasers (to less than 1 thou).

I had some pictures, but have lost them - if you would like to see the idea, I will post them again.
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Offline RICH

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Re: Limit switches
« Reply #4 on: November 29, 2008, 06:50:53 AM »
Repost the pic's along with some info on the switches. One of these days I may decide to use them.