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Author Topic: Limit switches  (Read 2376 times)

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Offline RonC

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Limit switches
« on: February 11, 2011, 03:20:02 PM »
Hi Guys,
I am having a problem wiring up my home switches, I have a Warco round column mill which I converted to CNC
some while ago and wired the switches in series and it works perfectly, I have recently built a 4' x 2' router table
 using the same type of electronics, a DIYCNC Optoport board, Zapp drivers and motors, and wired the switches
in series but when I try to home the machine it homes on Z and backs off the switch as it should then homes on Y
hits the switch and does not back off, it triggers an estop and I cant move off the switch.
I have auto override enabled as on my mill but it wont move even when I use manual override switch, I have to power
down and wind off by hand.
Any Ideas would be greatfully received,
Thanks in advance
Ron

Offline Hood

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Re: Limit switches
« Reply #1 on: February 11, 2011, 04:25:08 PM »
Sounds like your switch is not positive snap action, in other words when the Y is hit it opens but as Mach reverses the axis the switch closes instantly then opens and then closes again thus the limit error.

Auto override should be allowing you to reset and jog off but again if the switch is constantly bouncing open/closed then Mach will see you come off the switch (closed) but it then opens again and another E-Stop is triggered.

You could try increasing the debounce interval to 2000 on General config page but probably best to sort the switch out.
Hood

Offline RonC

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Re: Limit switches
« Reply #2 on: February 11, 2011, 06:25:24 PM »
Hi Hood,
Thanks for the quick reply, the switches are micro switches as used on my other machine,
totally forgot about the debounce setting, Dohh!, will try out tomorrow and let you know.
Cheers
Ron

Offline Hood

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Re: Limit switches
« Reply #3 on: February 11, 2011, 07:10:38 PM »
Still could be a bad switch on the Y, debounce may mask the problem but personally I would replace the switch.
Hood

Offline RonC

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Re: Limit switches
« Reply #4 on: February 12, 2011, 07:53:22 AM »
Hi,
I have swapped the switch and upped the debounce, still the same result.
Here is the full story, when I built the machine I had the same problem and I got round it by
having each switch on a separate input,  that works perfectly, that left me 2 inputs, 1 for E stop and 1 for my probe
The other day when I went to run a job I noticed that the green light on the probe input was on all the time,
when I checked it out I found that there was no voltage on the bob pin, should be 5 volts, when not connected to anything.
I have Emailed Roy at DIYCNC, and am waiting for a reply. So that means I have no probe, so I thought give it another go
and see if I could put the switches in series but no go. Every time it hits the second switch it will not back off, I have put the Z axis
on its own input with Y and X in series on another input Z homes and backs off, Y homes and backs off, X homes and locks up, always the second switch!!
If any one has any ideas I am all ears!!!

Thanks
Ron

Offline djc

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Re: Limit switches
« Reply #5 on: February 13, 2011, 03:59:30 AM »
...I have put the Z axis on its own input with Y and X in series on another input Z homes and backs off, Y homes and backs off, X homes and locks up, always the second switch!!

A few random things.

1. check your configuration in ports and pins. Make sure you haven't accidently swapped an active low for active high or port 1 to port 0 or 2.
2. put an LED and resistor in the circuit so you see what's going on.
3. if it is X that you are having a problem with, why not put that on its own input and share the other two until the cause is identified?
4. X does not home in a different direction to the other two does it (i.e. Y & Z home from positive towards zero; X homes from negative to zero or zero to positive)?
5. check the numbers and buttons in the homing dialog.
6. disable the other two axes and get X working on its own. Add stuff back in one part at a time.

Offline RonC

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Re: Limit switches
« Reply #6 on: February 13, 2011, 06:34:23 AM »
Thanks for all the suggestions guys, I have ripped out all the switch wiring
and have relaced all cables with new screened cable (old cable was screened)
and all seems to be working OK. Don't know if there was a bad connection on the screen
and picking up interferance or what, but seems OK now.
Thanks again
Ron