Universal g-code sender miss triggered hard limit error when Spindle motor start spining

[weigang]

hello, i don't kwow is right to post this here, but i really have no idea with my diy cnc machine:

my board is arduino uno + CNC Shield v3
firmware: GRBL v1.1h
software: Universal G-Code Sender v2.1.6

i added six microswitchs as hard limit, and set $21=1 to enable these, works fine.

now the problem is when i start Spindle motor Manual, the ugs rasied message:

An error was detected while sending '$G': (ALARM:1) Hard limit has been triggered.

and the machine halted, can not make any move unless i stop the motor. but the motor and arduino complete with no Electrical connections,

if i use set $21=0 to disable these hard limit microswitch, the problem won't happen, but i really want to keep hard limit.

any advice is welcome, thank you.

[groundFungus]

Your spindle motor is injecting noise onto the power supply. I had the same thing happen and just decided to not use hard limits.

Put 0.1uF caps on the motor to bypass noise.

Put 0.1uF ceramic caps from the switches to ground to bypass noise. Put the caps right on the switches.

Get all limit switch wiring as far as possible from any motor power wiring.
If the only pullups are the internal pullups (30K-50K) on the limit switches, decease the pullup resistance (stronger pullup). Try 10K and go down from there.

[Grumpy_Mike]

@weigang

hello, i don't kwow is right to post this here, but i really have no idea with my diy cnc machine:

No,
The obvious place is about CNC devices.
Let me move it for you,

[weigang]

thank you for your quick reply to me, for your suggest, i study and try to use soft limit, and maybe i will try to add the Component to bypass Electronic noise later. thank you again, you really help me a lot

[weigang]

hello, i have tried, but it looks not well (forget to say, my Spindle motor is ac110v 500w)...

i added ceramic caps on motor circle, added 10k resistance on limit micro switches, first time to try, it's not working, the problem is same as the title of this topic.

second time, when i start motor for seconds, one of the ceramic caps has explode (as the red circle of the image below), and the fuse of the power adapter of motor is blown...

you see, I have a little no confidence now... the good thing is I have studied soft limit on UGS, the engraving operation even won't start if the ugs compute there is risk of collide. well, it's nice, that's good enough:)