Unable to Start or Finish Homing Cycle

I just finished building an ACRO1010 laser engraver using an Arduino Mega 2560 controller running Grbl 1.1g. The engraver works great, except I have never been able to use the Homing Cycle.

When homing is turned on, the machine boots in alarm state, as it should. I enter $X to reset and then $H to home. The machine just sits there - no movement with either axis. After about a minute or so it goes back into alarm state. Since the machine is trying to home, I can't use '?' to see what is happening. If I disable the homing cycle the machine works fine, I just manually home it.

I'm using limit switches supplied with the kit in a "normally open" mode. I have confirmed they are working correctly with a continuity tester on the Arduino pins. I'm using Pin10 for X-Axis and 11 for Y-Axis. I also disabled Z-Axis homing in config.h, by commenting out the homing definitions and replacing them with:
#define HOMING_CYCLE_0 (1<<X_AXIS)
#define HOMING_CYCLE_1 (1<<Y_AXIS)
#define N_HOMING_LOCATE_CYCLE 1

I'm new to laser engraving and Grbl, so I'm not sure how I can see what is happening to determine where I messed up. A log of a recent attempt is below along with my configuration settings.

Any suggestions or ideas are greatly appreciated!

Thanks,

Jim

In the following the machine does not move after the $H commands.

Waiting for connection...
Waiting for connection...
Grbl 1.1g ['$' for help]
[MSG:'$H'|'$X' to unlock]
error:9
[MSG:Caution: Unlocked]
ok
?
<Idle|MPos:0.000,0.000,0.000|Bf:35,254|FS:0,0|Pn:XYZR|WCO:0.000,0.000,0.000>
ok
$i
[VER:1.1g.20180813.Mega:ACRO1010]
[OPT:VNM+,35,255]
ok
?
<Idle|MPos:0.000,0.000,0.000|Bf:35,254|FS:0,0|Pn:XYZR|Ov:100,100,100>
ok
$H
?
ALARM:8
ok
Grbl 1.1g ['$' for help]
[MSG:'$H'|'$X' to unlock]
[MSG:Caution: Unlocked]
ok
?
<Idle|MPos:0.000,0.000,-10.000|Bf:35,254|FS:0,0|Pn:XYZR|WCO:0.000,0.000,0.000>
ok
$$
$0=5
$1=255
$2=0
$3=0
$4=1
$5=1
$6=0
$10=3
$11=0.005
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=1
$24=250.000
$25=50.000
$26=25
$27=10.000
$30=1000
$31=0
$32=1
$100=230.620
$101=230.620
$102=500.000
$110=3000.000
$111=3000.000
$112=500.000
$120=15.000
$121=15.000
$122=10.000
$130=914.000
$131=914.000
$132=500.000
ok
$X
ok
$H
ALARM:8
ok
Grbl 1.1g ['$' for help]
[MSG:'$H'|'$X' to unlock]
[MSG:Caution: Unlocked]
ok
?
<Idle|MPos:0.000,0.000,-10.000|Bf:35,254|FS:0,0|Pn:XYZR|WCO:0.000,0.000,0.000>
ok

 

Hi Peter I looked at that option. I'm using an Arduino Mega 3560, the wizard only allows me to select an Arduino Uno or Nano. Do you know which one I should select?

Thanks,

Jim

 

Thanks for the insight about the 2560. I was not aware of the stability issues. I may look into an Atmega328 as an alternative.

 

I found an UNO from an old project. Reflashed it with an empty program to clear it out, then used the Flash Wizard to flash it with the 2 axis option. I'm making progress, but it's still not Homing right. Now when I home, the x-axis will move to the left (-x direction) for 5 mm, pause, then move left for 5mm. Next the y-axis will move closer (-y direction) for 5 mm, pause, move 5mm closer, then stop. It appears the home cycle completes at this point. I have the gantry in the middle and it does not contact any limit switches. If I change the pull off distance from $27=5 to $27=20. It moves in 20mm increments as described above.

I have the x-limit switch in pin 9 and the y-limit in pin 10 of the UNO. My current config is below. Any ideas on what is causing this and how to fix it are greatly appreciated.

[21:06:48] [ $$ ] ok
[21:06:48] [ $I ] [VER:1.1g.20181112:ACRO1010]
[21:06:48] [ $I ] [OPT:V,15,128]
[21:06:48] [ $I ] ok
[21:06:59] [ $$ ] $0=5 ;Step pulse time, microseconds
[21:06:59] [ $$ ] $1=255 ;Step idle delay, milliseconds
[21:06:59] [ $$ ] $2=0 ;Step pulse invert, mask
[21:06:59] [ $$ ] $3=0 ;Step direction invert, mask
[21:06:59] [ $$ ] $4=1 ;Invert step enable pin, boolean
[21:06:59] [ $$ ] $5=0 ;Invert limit pins, boolean
[21:06:59] [ $$ ] $6=0 ;Invert probe pin, boolean
[21:06:59] [ $$ ] $10=2 ;Status report options, mask
[21:06:59] [ $$ ] $11=0.010 ;Junction deviation, millimeters
[21:06:59] [ $$ ] $12=0.002 ;Arc tolerance, millimeters
[21:06:59] [ $$ ] $13=0 ;Report in inches, boolean
[21:06:59] [ $$ ] $20=0 ;Soft limits enable, boolean
[21:06:59] [ $$ ] $21=0 ;Hard limits enable, boolean
[21:06:59] [ $$ ] $22=1 ;Homing cycle enable, boolean
[21:06:59] [ $$ ] $23=0 ;Homing direction invert, mask
[21:06:59] [ $$ ] $24=500.000 ;Homing locate feed rate, mm/min
[21:06:59] [ $$ ] $25=200.000 ;Homing search seek rate, mm/min
[21:06:59] [ $$ ] $26=250 ;Homing switch debounce delay, milliseconds
[21:06:59] [ $$ ] $27=5.000 ;Homing switch pull-off distance, millimeters
[21:06:59] [ $$ ] $30=1000 ;Maximum spindle speed, RPM
[21:06:59] [ $$ ] $31=0 ;Minimum spindle speed, RPM
[21:06:59] [ $$ ] $32=1 ;Laser-mode enable, boolean
[21:06:59] [ $$ ] $100=230.620 ;X-axis steps per millimeter
[21:06:59] [ $$ ] $101=230.620 ;Y-axis steps per millimeter
[21:06:59] [ $$ ] $102=250.000 ;Z-axis steps per millimeter
[21:06:59] [ $$ ] $110=3000.000 ;X-axis maximum rate, mm/min
[21:06:59] [ $$ ] $111=3000.000 ;Y-axis maximum rate, mm/min
[21:06:59] [ $$ ] $112=500.000 ;Z-axis maximum rate, mm/min
[21:06:59] [ $$ ] $120=10.000 ;X-axis acceleration, mm/sec^2
[21:06:59] [ $$ ] $121=10.000 ;Y-axis acceleration, mm/sec^2
[21:06:59] [ $$ ] $122=10.000 ;Z-axis acceleration, mm/sec^2
[21:06:59] [ $$ ] $130=914.000 ;X-axis maximum travel, millimeters
[21:06:59] [ $$ ] $131=914.000 ;Y-axis maximum travel, millimeters
[21:06:59] [ $$ ] $132=200.000 ;Z-axis maximum travel, millimeters
[21:06:59] [ $$ ] ok

 

Hi Rob - Thanks for the advice on the noise issue. That solved the problem! After I verified in the troubleshooting tab the swithes were set correctly, I added the 0.0uF cap filters. That cleared up the issue immediately. I had the limit switch wire running inside the vrail for both x and y axis.

I was surprised it was noise. I thought that the noise would trigger 'false positives' with the switches. I did not see anything like that in the troubleshooting tab.

Regardless, it's now working and I appreicate your and Peter's help in resolivng my problem. I was going crazy trying to figure it out.

Jim