New to EMC configuring limit switches

Hi all,
I am wondering how to set up the limit switches on my Knee mill that i plan to control using EMC2

I notice that in the pinouts EMC says limit/home for each axis. does this mean that one limit switch per axis is all that is required to operate the machine? Ie the machine will know which direction it was moving so it can alarm "over travel X positive" or similar. this is set up by positioning the limit centrally to the axis travel and having a ramp at each eng to trigger the switch...

does the machine then move toward X0 Y0 Z0 till it hits the limits and knows that it is home?

I am asking these questions as i need to know how many limit switches i will need to buy and wire up...

thanks

Andrew

BigJohnT wrote:

EMC2 doesn't require any limit or home switches. You can have any combination of limit/home switches. For EMC2 to know which limit has been tripped you need two switches for each axis, one for each direction limit. If you have enough inputs then a limit at each end and a home switch where ever you want it is nice to have. The best way to wire limit switches is for them to be normally closed so if you loose a wire the machine thinks it is on a limit instead of merrily crashing into the hard stop. Also position the limit switches so the axis will stop after tripping the limit before it hits the hard stop.

The homing sequence is how you define it. Read about HOME_SEQUENCE here:

www.linuxcnc.org/docview/html//config_ini_homing.html

John

ok. thanks

I don't think i will have enough inputs on the breakout board to run that many switches... it has 5 inputs 6 would have been good:(

so can EMC recognize a second serial port with an additional breakout board to accommodate the desired inputs?

cheers

Andrew

Are you using stepconf ? You can choose 'all limits' and connect all the limit switches in series, so would only use one parallel port input pin.
The same can be done with the home switches.
EMC can recognize up to 8 Parallel ports (I assume that is what you meant not serial) though stepconf only helps with three.
stepconf also doesn't help you set up signals on the extra two parallel ports, you must do that in a custom file.

cmorley wrote:

Are you using stepconf ? You can choose 'all limits' and connect all the limit switches in series, so would only use one parallel port input pin.
The same can be done with the home switches.
EMC can recognize up to 8 Parallel ports (I assume that is what you meant not serial) though stepconf only helps with three.
stepconf also doesn't help you set up signals on the extra two parallel ports, you must do that in a custom file.

yes I'm assuming i mean parallel to;)

I haven't had much of a chance to muck around with it yet as the computer with the install isnt setup yet. i have just been having a bit of a look at the cd...

I have just been trying to work out what i should be buying to best get the job done. i have been buying almost everything via ebay from international sellers so need some planning so i dont get any unwanted delays...

can someone please explain how the homing sequence works with the home switches connected in series? how does it know if it has hit a switch?

thanks

Andrew

after reading the link to explain the homing sequences i think i will use 6 limit switches. 3 wired in series for X,Y,Z positive and negative. the machine wont alarm as to which limit has been triggered but i don't plan on running into them often and it should be reasonably obvious which has been tripped.

for the home switches i will use one per axis wired individually. this will leave 2 spare inputs in the breakout board. i will use one for the e-stop and the other is free at this stage.

are there any other required inputs that i am missing?

thanks again

Andrew

BigJohnT wrote:

If your going to do a lot of setups a MPG is very handy. One with axis and increments selectors is even handier.

John

yes I have been wondering what is involved in setting one of these up?

was hoping to be able to make one... where does one plug such a device in? and is it feasible to make one?

cheers

Andy

I think it is time to boot up the computer that will run the show. stepper motors and drivers will arrive within 2 weeks and i am waiting for a quote to do the required machining on the ball screws. getting close (ish...)

There is some great information on the subject here wiki.linuxcnc.org/cgi-bin/emcinfo.pl?EmcKnowledgeBase
Also look at wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Simple_Remote_Pendant and wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Add...imple_Remote_Pendant

Rick G

thanks. it's going to take a fair bit of reading before i get my head around all this...

looks possible then but i might get the mill up and running first before i stick the time into this one...