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Author Topic: series limit switch configuration using one for the home as well  (Read 6354 times)

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Offline geone

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series limit switch configuration using one for the home as well
« on: September 19, 2011, 12:48:44 PM »
The documentation indicates that limit switch(s) can also be assigned as a home switch.  I have all limit switches set to port 1, pin 11 (in this case) and used the autoset for each.  Using limit switch only configuration, the system identifies the switches and they work as expected.  Assigning one on each axis as a home switch will cause the axis to begin to home, but when the switch is hit, the system just reacts as a limit switch and will not back off....any suggestions

thanks
geo

Offline BR549

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Re: series limit switch configuration using one for the home as well
« Reply #1 on: September 19, 2011, 12:57:33 PM »
It is probably switch bounce causing the problem. IF the switch contact bounces (most do) then it see it as a SET/Reset and does not move further. AS then you are still sitting on the switch when it switches BACK to limit mode it thinks it has tripped the limit (catch22)   

Try adding in some Debounce start at 2000.  Then if needed adjust it down until you see the problem then split the difference.

Just a thought, (;-) TP
« Last Edit: September 19, 2011, 12:59:37 PM by BR549 »

Offline geone

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Re: series limit switch configuration using one for the home as well
« Reply #2 on: September 22, 2011, 01:35:14 PM »
is there a value that is too high.....I seem to get stability at about 4500?
thanks
geo

Offline Fastest1

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Re: series limit switch configuration using one for the home as well
« Reply #3 on: September 25, 2011, 12:43:17 PM »
geo, The number used for the debounce is a measure of time that Mach must see the signal to be recognized. In your case if you are using a time interval of 4500, your machine is still moving after the initial signal was begun. At high rates of speed this could be detrimental i.e. a crash. The ideal number would be 0. This is not an unobtainable number but you will have to pay attention to wiring detail, grounds and shielding.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: series limit switch configuration using one for the home as well
« Reply #4 on: September 25, 2011, 12:56:43 PM »
Let me elaborate on my calculation just to clarify it in my own head. Each unit on the debounce setting is 40us (40 microseconds). So if you are setting your debounce at 4500. This is 40us x 4500=180,000 microseconds. Or .18 of a second. That is an eternity. How far does your machine travel in this time at full rapid? How delicate are your switches?  
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: series limit switch configuration using one for the home as well
« Reply #5 on: September 25, 2011, 01:01:37 PM »
Does your Reset start flashing for no apparent reason? Have you run your limit switches successfully (not as home switches) with a low (under 250?) or "0" debounce setting? If you are having to set your debounce that high there must be a lot of noise, I would sure think it was triggering a fault in Mach.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline geone

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Re: series limit switch configuration using one for the home as well
« Reply #6 on: September 27, 2011, 01:46:29 PM »
I have wired the switches in series with a woven wire shielded conductor (stranded) and tested all to confirm proper working condition.  I talked to another gentleman who indicated that the noise may be coming from my power supply (which is right next to the input terminals on the breakout board.  He suggested that I power the board with another power supply other than the one powering the drivers (any thoughts there?).  Beyond that, I am lost for a solution other than to install expensive shielded micro switches or run with soft limits.

thanks for all the info
geo

I am using a C35 breakout board from CNC4PC
SD-2H086MB drivers (80vdc)
PS-6N80 power supply (AnTek Inc)
Mach3 latest locked version


Offline Hood

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Re: series limit switch configuration using one for the home as well
« Reply #7 on: September 27, 2011, 02:49:07 PM »
Do you have the shield connected only at the control end to a single Earth stud in your control?
Hood

Offline geone

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Re: series limit switch configuration using one for the home as well
« Reply #8 on: September 27, 2011, 03:31:19 PM »
i may have a misunderstanding of how the shield works....I presumed that the shield (ground and alum) in and of themselves would divert noise.  I have not actually grounded the lead to a ground source on the breakout board.  I am using a usb power line to the board (it is grounded at the power source, but shield ground portion of the cable has not be connected to a ground port on the board.  So call me dumb...but if I were to connect the outer portion of the cable (not the alum wrap) to the ground on the board...good to go?
thanks
geo 

Offline Hood

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Re: series limit switch configuration using one for the home as well
« Reply #9 on: September 27, 2011, 03:38:32 PM »
Gnd and Earth (where the shield connects) are different things. You should really have a stud of some kind in your cabinet that is connected to your supplies Earth connection and all shields should be connected to that stud. Some breakout boards do provide connections for Shield but most dont.
Hood