what are the correct settings for NC limit switches

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jrdarrah
Posts: 5
Joined: Sun Mar 18, 2018 10:38 pm

what are the correct settings for NC limit switches

Post by jrdarrah » Mon Mar 19, 2018 12:17 am

I''m just getting started with the CNC shield and so far I can make the motors spin. I was doing some experimenting with just the board before wiring up the mill. I have the End Stop jumper set to high. I have jumpers representing the NC switch on Z+, Z-, Y+, Y-. No jumpers on X+ or X-.
My settings are

Grbl 0.9j

$0=10 (step pulse, usec)
$1=25 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=0 (dir port invert mask:00000000)
$4=0 (step enable invert, bool)
$5=1 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=19 (status report mask:00010011)
$11=0.010 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=0 (report inches, bool)
$20=0 (soft limits, bool)
$21=1 (hard limits, bool)
$22=1 (homing cycle, bool)
$23=0 (homing dir invert mask:00000000)
$24=25.000 (homing feed, mm/min)
$25=500.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=1.000 (homing pull-off, mm)
$100=250.000 (x, step/mm)
$101=250.000 (y, step/mm)
$102=250.000 (z, step/mm)
$110=500.000 (x max rate, mm/min)
$111=500.000 (y max rate, mm/min)
$112=500.000 (z max rate, mm/min)
$120=10.000 (x accel, mm/sec^2)
$121=10.000 (y accel, mm/sec^2)
$122=10.000 (z accel, mm/sec^2)
$130=200.000 (x max travel, mm)
$131=200.000 (y max travel, mm)
$132=200.000 (z max travel, mm)

the ? command gives -- <Idle,MPos:0.000,0.000,-1.000,WPos:0.000,0.000,-1.000,Lim:111>
a G90 then
X10 Y10 Z10 spins all three motors which makes sense based on the Lim:111. My expectation was that Y & Z would move but not the X. Is that correct, if one limit switch trips it only affects that axis or is it if any limit switch trips then all three axes stop?

My question is why are all three limits showing 1 when I only have the jumpers on the Z & Y pins? What am I doing wrong?

bruceg
Posts: 1
Joined: Sun Nov 11, 2018 5:20 am

Re: what are the correct settings for NC limit switches

Post by bruceg » Sun Nov 11, 2018 5:39 am

All the limit switches are held Hi by separate, switchable resistors built in to the Arduino microprocessor. This is the default for grbl.
So regardless of whether a switch is connected they ALL will show as '1' (+5V).
Vr 3.1 (and later?) CNC Shield has 3 extra pins to allow supporting different grbl versions -
For older versions of grbl you tie the outer limit pins to Gnd with a jumper between High/Low. Recommended wiring of limit switches is NO.
For > 0.9 jumper End Stop | High and the outer pins will be assisted to +5V. Recommended wiring of limit switches is NC.

Note that command 5 will invert the response to the switch value, $5=0 is normal response, $5=1 is opposite.

bye.

Bertus Kruger
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Re: what are the correct settings for NC limit switches

Post by Bertus Kruger » Fri Nov 16, 2018 2:21 am

This might help... viewtopic.php?p=9873#p9873

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