I am new to CNC and built my CNC machine. I have limit switches on all axis for homing. I have use shielded cable for all switches and grounded the shields. I even used a Optocoupler for connection to the controller (Arduino GRBL) But I still get false triggers. I have some other things to try like small caps across the switches and ferrite Rings around the cables. But for the time being Is there a way I can send a code to turn off the homing before starting the cutting operation and back on after the operation is complete.
You surely do need caps across the switches,but there are many other things .
Perhaps some more info about your setup , lots more ,there is no such thing as too much.
There are many here who may help you but there is no context unless you give these details.
Cancelling homing while running could be done but finding the problem is best. Try the caps ,it worked for my home made arduino uno setup . But there i go stabbing in the dark!
How are you grounding your shielded cables?
Also how long are your runs ? Do they come near your stepper cables/motors.
A good place to start is to only connect the shield at one end, usually the ground closest to your controller.
Depending on the quality of your shielded cable you may also need shielded cable on your stepper lines as well. Especially if you’re running your limits in the same cable tray/cable track as your stepper drivers.
If all else fails, using non contact limit switches is always a good option too.
1 Like
the Arduino axis limits use the neg voltage for circuit closed, so i would not think noise ( induced voltage) is the problem, maybe chatter is causing the limits to make. try running a project with no bit ( not cutting) as a test.
I use R/C filters on my CNC projects, even with quality shielded cable. Are you using a Uno with a Protoneer shield? Protoneers have built in RC filters, the other shields do not AFAIK.